* 1949 - 1964 * 1964 - 1990 * 1995 - Present

Submit corrections and additions to this information to The Olds FAQ Compiler.

A note about common engine displacement among divisions:
While it may be hard to believe in today's era of corporate engines, each GM division, at least through the mid-70s, unlike Ford and Chrysler, had their own unique engine designs. Despite common displacements, all used different bore and stroke combinations with completely different blocks and heads (and everything else). This applies back to the 30's and farther. In the 60's, 70's, and 80's, many divisions and makes built common displacement engines, say 350, 400, 425, and 455.

For example, the Buick, Chevy, Olds, and Pontiac 350s are all totally different, using different bore/stroke dimensions, different block and head castings, and different reciprocating parts. About the only things common among these four motors are the distributor cap and the carb bolt pattern (assuming a Q-jet - the Holley used on some Chevy motors is obviously different). Things like bearings, accessories, sensors and engine add ons are another story.

As an example, the Buick mounts its distributor in the front, while the other three mount it in the back. The Chevy distributor passes through the intake manifold, while the Olds mounts to the block aft of the intake. Even the distributor housings are different among the four.

The same applies to the 454/455 motors; each division had their own proprietary design. None of the castings or internal components are interchangeable (well, at least, not without a lot of machine work - one trick is to put Buick rods in an Olds 455, but this requires a lot of custom work). To make it even more complex, the big and small block Chevy motors are totally different, unrelated designs. Pontiac, on the other hand, uses a single engine block to produce 350s and 455s though there is a difference between early and late Poncho motors). Olds simply raised the deck height on their small block casting about an inch to accommodate the 4.25" stroke of the big block 455.

The above is a simplification, but the bottom line is that virtually nothing is interchangeable among the engines of the different GM divisions, without a lot of machine work.

I'm no expert, but i understand there is really no such thing as a "torque engine", or "hp engine", as hp is derived mathematically from the measurement of torque. It's interesting that all engines have the same torque as hp at 5250 rpm. I also think that Olds engines are called torque engines because they usually produce a higher torque figure than hp, but i believe this is due to the torque peak being reached at a relatively low rpm.

If you look at a dyno sheet from an engine producing very high hp at high rpm, the torque and hp lines still cross at 5250, but the hp continues to climb. I think most fellows who have good luck modifying factory cylinder headed Olds engines are aware of the cylinder head's limitations, and try to come up with a parts combo that will produce max power peak at a lower rpm.

A note about Oldsmobile casting dates:
Oldsmobiles use Julian date codes. All you will see is a number cast into the part from 1 to 365. It will look like a plate with the date was screwed into the mold for the manifolds. Unlike Chevy, which uses actual dates (like 3 C 69, for March 3, 1969), Olds will cast 62 for the 62nd say of the year. For originality and number matching authentication, make sure your julian date codes fall before your car was produced. Look on your block to the pasenger side of the distributor for you block date. Then make sure your manifolds were cast within a few weeks of the block.

[ Thanks to Tony Waldner for this information. ]

Engines 1949 - 1964

This generation of engines are basically the same dimension block, heads etc.

Used a dry manifold. In other words, the intake manifold can be taken off of the engine without uncovering the lifter valley (like the Pontiac V-8).

Original paint color can help identify an engine. However, since paint is easily changed, it should be used as supporting evidence, not as absolute indication of engine lineage.

The engines were sometimes named, and this was printed on the air cleaner label or sticker. The SkyRocket was a 394 available from 1961 thru 1963, and was standard on Ninety Eights and Super 88s. It was an option on Dynamic 88s. 1964s were known as plain Rockets, which seems strange.

Vehicle ID Plate Location:

1935 - 1940 On frame left side rail under hood
1941 - 1948 On upper left front face of dash
1949 - 1965 On left front door pillar

The Vehicle ID plate breaks down as follows:

Digit   Meaning
  1     Number of cylinders (6 = V-6, 8 = V-8)
  2     Engine series (engine id)
  3     Model year
  4     Plant (M = Lansing, MI)
 5-10   Vehicle build number

Engine Series (Number) Location:

1935-50 Straight six On upper left corner of cylinder block
1949-50 Straight eight On left hand bank of cylinder block.
1949-56 303, 324 V-8
1957-64 371, 394 V-8 Top of center exhaust port of left cylinder head.
1961-63 215 V-8 On right of front cylinder head. Turbo engines have a "T" prefix.

Here are some engine unit numbers:
Number Year CID Notes/Location
A001001 1957 371 Motor series number was placed on a "boss" on the top of the center exhaust port on the driver's side.
B001001 1958 371
C001001 1959 371
D001001 1959 394
H001001 1960 371 Used on some 371 engines.
C001001 1960 371
D001001 1960 394
S001001 1961 215
D001001 1961 394 Different application than F & G.
F001001 1961 394 Different application than D & G.
G001001 1961 394 Differnet application than D & F.

Then in 1962 there were letters all over the place! BTW the above #s were not for engine ID as there were more model specific numbers that were 577( )1001 in 1957 and 620( )1001 in 1962 and on the front of the left cylinder head. In 1963 they went to semi-standardized VIN codes.

This info w/o permission from the "Standard Catalogue of Oldsmobile."

[ Thanks to Karl Aune, Paul Hartlieb, Bill Culp, Scott Clark for this information ]

What CIDs

These engines were produced between 1949 to 1964 in 303, 324, 371, 394 CID. On 1959-1963 engines, the 371 has gold valve covers, and the 394 has green valve covers.

CID   Years       Bore   Stroke   Series   Color
303   '49 - '53   3.750  3.4375
324   '54 - '56   3.875  3.4375   7, 8, 9
371   '57 - '58   4.000  3.6875   7, 8, 9
371   '59 - '60   4.000  3.6875   7        Gold
371   '61 - '63   4.000  3.6875
394   '59 - '60   4.125  3.6875   8, 9     Green
394   '61 - '63   4.125  3.6875   2, 5, 8  Hi-comp Red; Lo-comp Green
394   '64         4.125  3.6875   4

Engine Performance

                           Comp.     Horse-
Year   Series        CID   Ratio     power      Torque    Induction
1949   88            303   7.5-1     [email protected]   [email protected]  2 bbl
1950   88            303   7.5-1     [email protected]   [email protected]  2 bbl
1951   88            303   7.5-1     [email protected]   [email protected]  2 bbl
1952   88            303   7.5-1     [email protected]   [email protected]  4 bbl
       Super 88      303   7.5-1     [email protected]   [email protected]  4 bbl
1953   88            303   8.0-1     [email protected]   [email protected]  4 bbl
1954   88            324   8.25-1    [email protected]   [email protected]  4 bbl
       Super 88      324   8.25-1    [email protected]   [email protected]  4 bbl
1955   88            324   8.5-1     [email protected]   [email protected]  4 bbl
       Super 88/98   324   8.5-1     [email protected]   [email protected]  4 bbl
1956   88            324   9.25-1    [email protected]   [email protected]  4 bbl
       Super 88/98   324   9.25-1    [email protected]   [email protected]  4 bbl
1957   All           371   9.25-1    [email protected]   [email protected]  4 bbl
       Tri-power     371   9.25-1    [email protected]   [email protected]  3 2bbls
1958   All           371   10.0-1    [email protected]   [email protected]  2 bbl
       All           371   10.0-1    [email protected]   [email protected]  4 bbl
       Tri-power     371   10.0-1    [email protected]   [email protected]  3 2bbls
1959   88            371   9.75-1    [email protected]   [email protected]  4 bbl
       Super 88/98   394   9.75-1    [email protected]   [email protected]  4 bbl
1960   88            371   8.75-1    [email protected]   [email protected]  4 bbl
       Super 88/98   394   9.75-1    [email protected]   [email protected]  4 bbl
1961   88            394   8.75-1    [email protected]   [email protected]  4 bbl
       Super 88/98   394  10.0-1     [email protected]   [email protected]  4 bbl
       F-85          215   8.75-1    [email protected]   [email protected]  2 bbl
       F-85          215  10.25-1    [email protected]   [email protected]  4 bbl
1962  D88            394   10.25-1   [email protected]   [email protected]  4 bbl
       Super 88/98   394   10.25-1   [email protected]   [email protected]  4 bbl
       Super 88/98   394   10.5-1    [email protected]   [email protected]  4 bbl
       F-85          215    8.75-1   [email protected]   [email protected]  2 bbl
       F-85          215   10.25-1   [email protected]   [email protected]  4 bbl
       F-85          215   10.25-1   [email protected]   [email protected]  Turbo(1bbl)
1963  D88/S88/98     Identical to 1962
       F-85          Identical to 1962
1964   Jetstar I     394   10.5-1    [email protected]   [email protected]  4 bbl
       Dynamic 88    394   10.25-1   [email protected]   [email protected]  see Note 1
       Starfire      394   10.5-1    [email protected]   [email protected]  4 bbl
       S88/98        394   10.25-1   [email protected]   [email protected]  4 bbl

Note 1: The Dynamic 88 came standard with a 2-bbl carb. The Starfire engine was standard on the 98 Custom-Sports Coupe (the "top of the line" 98). It was available as an option all the other 98s and the Super 88. The 330 HP S88/98 version was an option on the Dynamic 88.

[ Thanks to Scott Clark, Dan Gulino, Dave Paulison, Art Fuller for this information ]

Differences & Similarities

Parts might exchange from 1949-53 303, 1954-56 324, 1957-58 371 engines. 371 and 394 cranks might interchange (same stroke), as might 303 and 324 cranks (same stroke). Cams should be interchangeable. In general, the 324 and 371 can interchange a lot but not to the 394. Parts will not exchange with post-1964 engines (260, 307, 330, 350, 403, 400, 425 and 455). These 1949 to 1964 blocks are physically very different from the 1964 to 1990 blocks, at least in appearance.

You could call some for the cam grinders that were doing cams back in the 50's, like Isky and Crane (check Engle also), to see if they may still have some lying around. You'll probably need to have a stock cam reground. Cams for the 1964 to 1990 Olds blocks won't interchange with the 303, 324, 371 or 394.

Engle Cams is/was a California cam grinder, which were noted for their "hot" Oldsmobile cams in the early and mid sixties. Stone, Wood, and Cook (A/Gas Supercharged) original motors were Olds powered before they and others ultimately went to the Chrysler hemi.

You'd either have to find an NOS cam, or a new, uncut blank. I'm quite sure that nobody is making new blanks for the 394's. You might see if any of the major, older cam grinder might have one sitting on their shelves, and it might not be that overly expensive.

Engine Replacement
I guess the easiest option would be to replace the dead 394 with a running '64 394, but since those motors are not on every junkyard lot these days, there must be some alternative, and the best would be the one that keeps the existing motor-mounts/transmission/exhaust hookups.

Unfortunatly, if you plan on using the current exhaust, trans, and mounts, the only option is another motor of that family. While it is possible to transplant another engine and trans, it would by necessity have to be a Frankenstein with home-fabricated motor and transmission mounts. A custom driveshaft would probably also be in the equation. That kind of swap is by no means impossible, obviously. It's all just a matter of how much time and $$ you would want to throw at it.

Fuel Injection
Hilborn had a fuel injection setup of these things, at least I think it was Hilborn. I remember seeing a trick dragster with a late 50's old, port fuel injection, and stock velocity stacks for each intake. There were blower intakes for these guys as well.

Intake, Exhaust Ports and Manifolds
1954 and 1955 324s' have smaller intake ports and valves than the 1956 engines. There are port differences on at least the 371/394 engines. Intake and exhaust ports differ between the 371 and 394 engines. Exhaust manifolds differ in size and stud hole location. Intake manifolds do not swap either. 1955 and earlier four barrel intake manifolds won't fit a 1956 engine unless you put a dent in the lifter valley cover.

Exhaust manifolds also differ greatly. For headers try a custom header shop. About three years ago I bought a pair of "dual exhaust" manifolds from a 371. The only thing that made them dual exhuast was a factory cast block off for the right side manifold that bolted to my 394 manifold.


1957 and later cylinder heads will physically bolt on to 1949 to 1956 engines, but the port matchup on intake maniflolds will be off because different cylinder deck heights are used. 1957 and later cylinder heads have larger coumbustion chambers and valves.

The 394 might have a weakness in the cylinder heads, and they have a tendency to crack.

J-2 Tri-carb
J-2 engines were first made as an option in '57 and not in '56. They were basically the same engines as the standards. The only difference is that the compression ratio was upped from 9.5:1 to 10:1 and there was a tri-carb setup on it. It was only offered for two years, 1957 and 1958. The only difference in the 1958 was the camshaft.

The J-2 Tri-Power setup will NOT fit the 303, 324 or 394. There were differences between the 371 and 394, I believe in the port sizes. The 394 intake passages are much larger.

You can save the carbs and linkage. As far as performance intakes, Offy used to make intakes, like dual quads, 4 2bbls' and things like that. Offenhauser did make a nice 3x2 intake manifold. Although, Offenhauser and Weiand did make tri-carb, six carb, and dual quad aluminum manifolds for the early years (54-56). Also available was a dual-quad intake for a pair of 625 CFM Carters. The problem now is finding one at a reasonable price, to make yours a rare Tri-Power Oldsmobile. Your best bet for high performance, is a stock 4GC intake with a 625 CFM Carter AFB. Besides, the Offy manifold is aluminum and looks better.

The 1949 - 1964 early Olds engines use hydraulic lifters that are not adjustable. The 50's Olds engines were notorious for flat cams,dished lifters, and worn rocker arms. Usually the lifters are the first to fail.

One theory is that the cam lobes were too narrow for the amount of load from the valvetrain. One of the changes in the 394 over earlier Rocket V8's was a longer cam allowing for wider lobes.

You might have substantial wear on some componet(s) of the valvetrain. Are you experiencing a loss of power with the lifter noise?

First, pull a rocker panel cover and try to identify the culprits. Check for excessive wear in the rocker arms or any damaged push rods. Listening to and watching the rocker arms with the car running should help you narrow down the problem areas.

Second, if necessary remove the intake and valley tray. Loosen the rocker assemblies and check each lifter for excessive wear, cupping, or for a collapsed condition. If you find any of these, you should at least replace all the lifters. Inspect the cam lobes as much as you can.

This is a fairly simple procedure, that most of us can perform. Follow a shop manual and take you time. This was my first major surgery on an Olds 25 years ago. Replaced the lifters and got rid of that embarrassing rattle from my engine. Ran a lot better too.

Motor Mounts
As for motor mounts, I think (stress the think here) that the motor mounts are the same between 303, 324, 371 and 394 engines. So, in theory, you could use any 394 or 371 in that car (those are by far the most common motors in that family, and the easiest to find).

The motor mounts are completly different compared to later ('64-90) Olds engines. The early Olds motors use a single front engine mount that bolts to the timing cover/water pump housing, and then to the K member. In back, the motor shares two mounts with the transmission, that are bolted to the tranny crossmemeber. The engine/transmission mounting points form a diamond or maybe rhombus shape, with one rear trans mount, two middle engine/trans mounts, and one front engine mount.

Parts In General
There will be some trouble finding a few things, but generally, you can find any stock parts you need. Price is the problem. Parts for these beasts generally run more than the more common motors (like a $100 gasket set). Rod bearing and timing chains should be fairly easy to find locally for a good price. Kanter Products offers a complete line of parts to rebuild a stock 394.

And yes, finding parts for these things is only getting harder (believe me, I know!). Like you said, the easiest thing would be to find another 394, if a rebuild is too expensive. But, they are out there.

The bellhousing on these engines is different from the later Cad/BOP pattern, but the 303-394 motors share the same bellhousing bolt pattern. The engine has a bellhousing integral to the motor block. You might be able to fabricate a mounting plate that goes between the engine and trans. I've seen them to go between either a BOP to Chevy, and the other way around, so I'm sure it's possible.

The LaSalle transmission does bolt up, but you have to have a spacer between the engine block and transmission because the main shaft on the trans is about 3/8 too long.

Transmission Replacement
There were some people who wanted to know where to get the kit to convert from an older hydra-matic transmission and 303, 324, 371, 394 series engine, to a TH-350, 400, etc transmission. Get a hold of

Tanson Enterprises, Inc, Dept. H
2508 J Street
Sacremento, CA 95816

They have a catalogue of older Olds parts that you can request.

Convert your 1949-1964 Olds 303, 324, 371, or 394 to an up-to-date Powerglide, TH-350, TH-400 or TH-700R4 Transmission. Conversion kit includes all adapters, modified case, bolts and fasteners. Customer must supply transmission case and flywheel. It is kit #DS7080 Trans Conversion, $550.00.

Dave Smith Engineering
Performance Components For Oldsmobile
P.O.Box 607
Corona, CA 91718-0607
(909) 371-7040 Fax: (909) 371-7012
[ Thanks to [email protected], Doug Ahern, Bob Handren, Isagil, Scott Clark, Chris Witt, Clayton Pierce, Ken Snyder, Robert Barry, Paul Brillhart, Laurence Simpson for this information ]

Varieties of the Early Rocket

Olds 303s come in a few varieties:

[ Notice: ]Please refer to the 303 CID Engine detail section as well!

[ Thanks to for this information ]

Olds 324s come in a few varieties:

[ Notice: ]Please refer to the 324 CID Engine detail section as well!

[ Thanks to for this information ]

Olds 371s come in a few varieties:

[ Notice: ]Please refer to the 371 CID Engine detail section as well!

[ Thanks to for this information ]

Olds 394s come in a few varieties:

[ Notice: ]Please refer to the 394 CID Engine detail section as well!

[ Thanks to for this information ]

Engines 1964 - 1990

In the year 1964, Oldsmobile came out with a new small block (330 CID), and the next year a big block (400 and 425 CID). Over the years other displacements were added. The Olds 455 was a 1968 introduction, developed from the Olds 425 introduced in 1965, which was a tall-deck version of the 330 engine design introduced the previous year, both of which replaced the 394ci V-8, which was a development of the design introduced as the 1949 303ci "Rocket" V-8. Production of big blocks ceased in 1976, although some were used, not necessarily in cars, in the 1977 model year. Production of small blocks ceased in 1990.

The big and small block engine types are almost identical, with the big block having a higher deck than the small block. The bore centers are the same, since the only differences between the small-block and big-block Olds blocks are the deck height (9.33" and 10.625", respectively) and the main journal size (2.5" and 3.0"; diesel 350 used BB size mains, however).

Many internal parts interchange, but it is best to keep the big block parts on the big block and the same for the small block.

The engines were sometimes named, and this was printed on the air cleaner label or sticker. Mid 60's 425s were known as Super Rockets. Some featured Ultra High Compression on their labels.

Quick Identification

The large oil fill tube on the front of the engine, sticking up from the timing chain area, is a dead giveaway that it is an Olds engine. The distributor is found at the back of the block and it does not go through the intake manifold, but right into the block. Also the spark plugs will be above the exhaust manifolds with no need for heat shields.

The Block Code and/or Head Code can give you an idea, but some codes cover many years. The casting number is ususally nearby. Other than that, there is no method of determining the year of manufacture of an Olds block.

The valve covers are a distinctive shape. Straight running front to rear, with an arc connecting each end of the two lines, to define front and rear. From their sealing surface, the covers are curved as they meet their top. The top of the covers are flat, like someone cut off the curved top.

The thermostat cover/radiator hose has a special molded in bypass pipe for the waterpump.

The day of the year of manufacture is the big number right by the distributor hole.

Original paint color can help identify an engine, or further identify it. However, since paint is easily changed, it should be used as supporting evidence, not as absolute indication of engine lineage.

The VIN derivative stamping or engine unit number is on the left most side of the block or head, on the driver's side, just below the cylinder head, toward the front. The pad is part of the engine and will indicate the year of manufacture, but that is usually rusted beyond recognition, and it can be changed by restamping. Basically it IDs the car in which the motor was originally installed. It can provide some circumstantial info but not a positive ID.

The VIN derivative on 68-up blocks doesn't tie directly to the type of car it was installed in (unless you have some way to unambiguously trace the last six digits of the VIN), however it can provide some indirect evidence. For example, if the production plant (third place in the VIN derivative) was one at which no 442s were built (KC, for example), then it obviously isn't a 442 motor. Of couse, you have no way of knowing for sure that the heads were originally installed on that block or not.

For example, what this proves is that it could be a W-30 short block, but it could also be a Toro motor. W-30s were only built in Lansing, so if the VIN derivative had shown some other production plant, you would have positive proof that it was not a W-motor. Of course, if the motor is still in the car and the car is positively a W-30 and the last six digits of the VIN match, then it is a W-motor.

If the engine was replaced under warranty, the pad may be blank. Rubbing alcohol and Q-tips help to remove the grime and grit from the stamping.

1964-67 V-8 Engine:
Code is stamped on the right cylinder head. Unfortunately, this only applies to what was originally the driver's side head. This code consists of a prefix letter (330 V-8=T (1964-65) or W (1966-67), 400 V-8 = V), then a production sequence number, followed by a suffix code letter (L = Low compression, E = 2-bbl export, G = High compression, H = 4-bbl export). A 2-letter code on the oil filler tube identified the engine.

1968-later V-8 Engine
Have the last six digits of the VIN number, the year of the block, and the assembly plant stamped on the driver's side of the block below the cylinder head. A 2-letter code on the oil filler tube identified the engine.

You can use the VIN derivative number to ID the year. For 1968 and up blocks, this number is located on a pad just below the cylinder head on the front left side of the engine. This number will be stamped on a machined pad on the front driver's side of the block, just below the deck surface. Typically it will be covered with a power steering bracket or something, below the number one spark plug location.

This number should take the form of "35Mxxxxxx" where:
3 = Oldsmobile division.
5 = year of manufacture (8=68, 9=69, 0=70, ..., 4=74, 5=75, 6=76, etc.).
M = location of manufacture (M = Lansing, B=Baltimore, X = Kansas City, Z = Fremont, CA, etc).
xxxxxx = last six digits of VIN of car that motor originally came in (original car's sequential production number).

The letter indicating factory must match the letter in the sixth position of the car's VIN (it should also, of course, match the factory indication on the body data plate - in other words, for a Lansing-built car, the sixth place in the VIN would be an "M", the body data plate should indicate "LAN", and the third place in the engine ID should also be an "M").

Now, obviously this doesn't provide all of the information you're looking for, but you do get something. Year of manufacture is nice to know. Additionally, the manufacturing plant may provide some info as to the motor's original use. For example, if the letter is an "X", that signifies Kansas City, which only produced full size cars (88s and 98s). Framingham (the letter escapes me at the moment) built only A-bodies. Lansing, on the other hand, built all Olds car lines (surprise), so an "M" doesn't tell you much.

If the motor has a number stamped which doesn't match the above, it's a non-original motor from another car. If it doesn't have any number stamped at all, it could be one of two things. First, it could be a dealer-installed factory service block, which would come without a VIN derivative. The dealer should have stamped the new block with the VIN derivative, but may not have. The other possibility is that it's a 65-67 block (ie, a short-stroke 400 or a 425), as these motors did not have the VIN derivative stamped on the block. Note that obviously this latter option can be checked by looking at the block casting letter ("D" for the 425, "B" or "E" for the 400 - as opposed to "G" for the correct 68 long-stroke 400).

Some blocks, before 1977, have thier ID cast above the right hand center freeze plug, eg. D for 425, F for 455. Olds didn't cast the displacement into the side of the blocks until they went to the light weight design in 1977. The 1977 and newer blocks will have the cubic inches cast in large raised numbers right above the right hand center freeze plug, eg. 403. The 307 will be in liters (5L), and a diesel engine will have the letters "DX" on it. The engine VIN letter will also be cast into the side of the block. Note that the 260 blocks sometimed have the last 3 digits of the casting number cast there, "355", which is rather misleading.

The VIN in 1972 and newer cars tells you what engine the car came with.

The number stamped on the oil filler tube is the engine unit code. The first number indicates the year the engine was assembled and the remaining numbers refer to the sequence number of the engine assembly (for identification at the engine assembly plant). This number has no link to any of the VIN data of the vehicle and does not contain any codes that identify the engine size.

From the factory, the oil filler tube had a sticker containing two letters which indicated components (carb, etc), model application (Cutlass, 88, etc), and other configuration items (timing, CA approved, etc). See the chassis manual for a list of available configurations. In 1973 and later, the factory did tune the emissions packages to the specific models that an engine might be installed in, but before that, in general terms, most engines were the virtually the same across all model lines.

Looking for information on the 442 CID engine? Check out the 442 section for clarification.

[ Notice: ] Check the Small Block Unit Numbers section for more information about VIN derivative numbers.

[ Thanks to Chris Witt, Joe Padavano, Bob Barry, Brad Otto, Jeff Easton for this information ]

Big Block CIDs

CID   Years      Bore   Stroke   VIN       Color
400   '65 - '67  4.000  3.980              Bronze
400   '68 - '69  3.870  4.250     H[,V]    Bronze
425   '65 - '67  4.126  3.975     O[,P,R]  Red; Toronado is Blue
455   '68 - '72  4.126  4.250     W        Red; Toronado & 1970+ is metallic Blue
455   '72 - '76  4.126  4.250     S,T,U,V,W  metallic Blue

High compression 425s and early 455s were painted red and the air clearners were an orange/red, definately a different shade from the engine. Low compression 425s had black air cleaners.

[ Notice: ] Check "Block" and "Head" sections for more information.

[ Thanks to Chris Witt, Mat Nadrofsky, Drew Senko for this information ]

Small Block CIDs

CID   Years      Bore   Stroke  VIN  Color           Notes
260   '75 - '82  3.500  3.385    F   metallic Blue
      '79 - '80  3.500  3.385        metallic Blue   Diesel
307   '80 - '84  3.800  3.385    Y   Black           No roller lifters, and w/5A heads: 150hp
      '85 - '90  3.800  3.385    Y   Black           Roller lifters, and w/7A heads: 140hp
      '83 - '90  3.800  3.385    9   Black           442, H/O engine; Roller
                                                     lifters w/7A heads '86 and up.
330   '64 - '67  3.938  3.385    T   Gold
350   '68 - '72  4.057  3.385    M   Gold
      '73 - '74    "      "      "   metallic Blue
      '76 - '80  4.057  3.385    R   metallic Blue
      '78 - '79  4.057  3.385    B   metallic Blue
      '80        4.057  3.385    8   metallic Blue
350D  '78 - '81  4.057  3.385    Z   metallic Blue   Diesel; Roller lifters '80 and up
350D  '78 - '85  4.057  3.385    N   metallic Blue   Diesel; Roller lifters '80 and up
403   '77 - '79  4.351  3.385    K   metallic Blue

All GM engines were painted black starting in 1983. It was due to better heat dissipation. From early 1977 to 1982, all GM engines were "corporate blue". Early 1977 and back, each division had their own unique engine colors, combinations, and usage (low & high compression, low & high performance, etc).

[ Notice: ] Check "Block" and "Head" sections for more information.

[ Thanks to Chris Witt, Tony Waldner, others for this information. ]

Is it a Big Block or Small Block (1964 - 1990) Engine?

There are three ways:

  1. A big block measures 14" between the heads at the manifold base, while a small block measure 12" between the heads at the manifold base.
  2. Facing the front of the engine, at the top surface of the timing chain area, to the left of the oil fill tube, there is a code about 1.5" high followed by the casting number. A letter indicates a big block, a number indicates a small block.
  3. A tell-tell sign is that the big blocks have a little hump in that area, whereas the small blocks are flat the whole way across.
[ Thanks to Chris Witt for this information ]

Differences & Similarities: Olds BB and SB

[ Notice: ]Make sure you read the Varieties sections for Olds big blocks and Olds small blocks as well!

There is an enormous amount of interchangeability between Olds engines from at least the 307 to the 455. Not everything will interchange, but many things will.

The gaskets for SB Olds and BB Olds are pretty much identical. The oil pan rails, front cover, water pump, fuel pump, and even head gaskets are the same. The major difference is the deck height of the block and thus the width of the intake (thus the difference in the intake tray gasket).

All stock Olds rocker arms, BB Olds or SB Olds, are the same size. Cams, distributors, carbs are the same.

Harmonic balancers really shouldn't be interchanged among displacements. If you look at a 403 balancer, its different from a 350, and a 455. A 260 balancer is different, and the 400s are different as well.

Only the 403 used siamesed bores, while all other engines (blocks) have water jackets between the bores. There's NO WAY that you can bore any Olds engine (block) to the 403's 4.35" bore size! You'd break into the water jackets (I believe that the outer casing of the cylinder might not even be 4.35" big!).

Then there is the entire category of valve train interchangeability. Chronologically:

Crank Shaft Bolt Pattern

All 1964 to 1967 Olds engines use what is call the early-style crankshaft bolt pattern, while all the 1968-1990 engines use the later patern. Thus two different flexplat/flywheel bolt patterns.

Engine Usage Across Models

After many years of owning tons of Olds muscle cars and countless hours researching engine combos, reading manuals and building engines I found out that the standard 442 AT engine, the W-33 Delta engine and the Toro W-34 engine are all identical. The only difference is the Toro's intake and oil pan. The cams, heads, pistons, and even the distributors have the same id #'s! These are all 1970 engines I am refering to.

It is funny how the public relations people at Olds advertised the compression ratio in the 442 at 10.5 to 1 and the W-33 Delta and the Toro W-34 were 10.25 to 1. The horsepower ratings were so varied on these 3 identical engines too! It was an interesting numbers game that Olds (and probably other makes) put down on paper.

The standard 442 MT engine actually came with a more radical cam than the W-30 AT, W-33 and the W-34. The W-30 AT short block is identical to the three engines mentioned above except for being "select fit".

Oil Pans

Standard capacity was four quarts plus one in the filter. Toronados used five quart pans plus one in the filter. Early pans incorporated a rear sump baffle. In the early to mid 70's this was dropped. Toronados also incorporated windage trays and baffles, but these were dropped in the early to mid 70's. In 1980 the Toronado oil pan was changed to a four quart version.

The later Toro 350 and 307 pans differ from rwd pans in appearance but not capacity. They look deeper and less wide. This is to clear the final drive unit. The 403 powered Toro's used in '77 and '78 use the same 6 quart pan as the early 425 and 455 cars, but they do not have the baffles that bolted to the main caps like the big motors did.

As for the dipstick difference's, they are the same length with full and add in the same locations. I think the 307 tube has a slight bend in it, if that makes a difference. FULL is the same distance below the pan rails. I investigated this extensively one time. Turns out there are a couple different std tubes & sticks to match. All correct matches have the same level at FULL. The Toro pan, being a bit narrower, has the ADD mark about 1/8" lower than others'.

There is a signifcant difference in big block and small block oil pans. There are 2 big blocks (Toro, and non) and the small blocks are all the same. My Olds engineering documents show three distinctive pans. PN's are 391440 (4 qts) for small block, 399270 (4 qts) for big block and 398438 (5 qts) for Toro. Pickup tubes are the same for both the 4 qt pans. The Toro has a different oil pump pickup.

[ Thanks to Tony Waldner, Bill Reilly, Chris Witt for this information ]

Over Square, Under Square

The G-block Olds 400 (1968 - 1969) has the worst bore-to-stroke ratio of any American V-8 ever made. Period. The undersquare 455 isn't too great, either. Of course, the Olds 350 has about the best bore/stroke ratio of any GM 350 motor.
[ Thanks to Joe Padavano for this information ]

PCV Differences, Rocker Covers

"Dual crankcase ventilation system for 455 cid engines equalizes crankcase pressure to allow normal oil flow at high engine speeds." Both valve covers have the "D" holes. In W-30, 455/4spd (OAI and non OAI cars), and W-33 applications, both valve covers used the rubber grommet with the large hole which accepts the black metal filter. This filter in turn connects to the air cleaner through the bent black metal pipe. Again, W-30s and 455/4spd cars used two, while 350s and AT non-W-30s used one on the passenger side only. In these applications, the driver's side valve cover had a rubber grommet with a smaller hole to accept the PCV valve.

All 442 air cleaners and W-33 Delta air cleaners have a rubber plug on the drivers side for dual ventalation. Finding an intake that is fitted with a PCV grommet would be much more difficult. Again, only W-30's and MT OAI 442's had these, and as every one knows the W's were aluminum and highly desireable! Just think, the iron intake with PCV fitting is actually more scarce than the almighty W-30 intake!!

[ Thanks to Jeff Easton, Tony Walder, Joe Padavano for this information ]

Year Differences

Early [pre-68] oil fill tubes had a simple smooth tubular top with a press-on oil fill cap. Late [68-up] oil fill tubes have a twist-on cap with correspondingly enhanced tube shape, AND an engine unit number stamped into the tube, the first digit of which matches the last digit of the year in which that engine hit the streets [well, model year, you know].
A few more differences:
Early:                             Late:
1964 thru 1967                     1968 and up
Big-neck PS pump                   Little 1" or so PS fill hole (1971+)
Early pattern flywheel/flexplate   Late pattern flywheel/flexplate
SB's= 330 CID                      SB's= 260, 350, 307, 403 CID
BB's= 400, 425 CID                 BB's= 400, 455 CID
Block= A, B, D, or E               Block= G, F, Fa
Heads= A thru C                    Heads= C and up
X/W or X/Y xst manifolds           W/Z xst manifolds, if lucky
Forged crankshaft                  Cast crank [99.9%]
45 degree cam required             39 degree cam required
   [except .921" lifter BB's]         [all engines]
No divided exhaust manifolds       May have divided exhaust manifolds
[ Thanks to Bob Barry, Joe Padavano, Tom Lentz for this information ]

Varieties of Olds Big Blocks

The big block of 1965 was initially available only in 425 CID with a 400 CID quickly added for the F-85 and 442 models (else why would some chassis manuals not include the 400 CID engine?). The highest performing version went into the Starfire with slightly lesser versions going into the Ninety-Eights and 88's.

Compared to Differences
425 455 crankshaft (stroke); connecting rods (stroke); pistons (compression height); one of: different lifter diameter (.921 vs .842), or cam bank angle (39 or 45); flywheel (early style); balancer. 455 is notched at the bottom of each bore to handle the connecting rod length.
Late 400 455 pistons (bore); balancer.
Late 400 425 pistons (bore); crankshaft (stroke); connecting rods (stroke); one of: different lifter diameter (.921 vs .842), or cam bank angle (39 or 45); flywheel (early style); balancer.
Early 400 425 pistons (bore); balancer.
Early 400 455 pistons (bore); crankshaft (stroke); connecting rods (stroke); one of: different lifter diameter (.921 vs .842), or cam bank angle (39 or 45); flywheel (early style); balancer.
Early 400 Late 400 pistons (bore); crankshaft (stroke); connecting rods (stroke); one of: different lifter diameter (.921 vs .842), or cam bank angle (39 or 45); balancer.

Olds 400s come in a few varieties:

1965 - 1967: The early 400 was produced from 1965 to 1967. It shared the same stroke as the 425. Early style crankshaft bolt pattern.

1968 - 1970: The late 400 was produced from 1968 to 1970. It shared the same stroke as the 455. Late style crankshaft bolt pattern.

[ Notice: ]Please refer to the 400 CID Engine detail section as well!

[ Thanks to for this information ]

Olds 425s come in a few varieties:

The Olds 425 introduced in 1965, was a tall-deck version of the 330 engine design introduced the previous year. Early style crankshaft bolt pattern.

1965 - 1967: Basically all were the same, with exceptions of compression (9:1 vs 10.X:1) and head valve sizes.

[ Notice: ]Please refer to the 425 CID Engine detail section as well!

[ Thanks to for this information ]

Olds 455s come in a few varieties:

The Olds 455 was a 1968 introduction, developed from the Olds 425 introduced in 1965. Late style crankshaft bolt pattern.

1968 - 1972: Basically all the same, with exceptions of compression (9:1 vs 10.X:1), head valve sizes, and carbueration. Rumored that nickle content dropped a lot in 1971. 1971 saw compression drop to 8.5:1 or 8:1.

1973 - 1976: Basically all the same, with exceptions of head valve sizes, and carbueration, but much more restrictive head ports than previous years. Rumored lesser nickle content as years went by.

1977 - 1978: It's been rumored and in some cases confirmed that a number of 455 blocks were used in 1977 and 1978 motorhomes, boats and irrigation equipment.

[ Notice: ]Please refer to the 455 CID Engine detail section as well!

[ Thanks to Bob Barry, Joe Padavano for this information ]

Marine and Irrigation engines

They were available in 1965-1967 as 425's and 1968 thru (at least) 1976 as 455's. I seem to remember seeing a listing in some factory literature referring to the 350 as being available as an irrigation engine as well.

The blocks, cranks and rods are the same as the passenger cars used. The 68-up 455's all used the same 258/272 duration, .435" lift camshaft. As near as I've been able to determine, all are high compression (including the 71 and up versions). Regardless of cylinder head casting, all used the big 2.072" intake valves. Hardened (pressed in) exhaust seats were used in ALL marine and irrigation heads.

Although I'm uncertain of the specific cylinder head castings used on some marine and irrigation engines, I can say for sure that the 73-76 versions used the KA heads. I believe the 1971 and 1972's used G castings. And C's on the 68-70 (although it is very possible the marine/irrigation C head was the CA head).

On the block ID pad, where the ID numbers go (front drivers side), there is a number that begins with an "L". This strange "VIN derivative" (or engine unit number) number starting with L denotes a marine motor. Some blocks were drilled for the clutch pivot ball, some not. The Ka heads were also marine pieces.

[ Thanks to Greg Rollin, Chris Witt, Joe Padavano for this information ]

[ Notice: ]Please refer to the Best Big Blocks section as well!

Varieties of Olds Small Blocks

Olds 260s come in a few basic varieties:

1978 - 1980: EGR, only 2 bbl carbs. Windowed main webs. In reality, however, you're not likely to blow out the bottom end of this motor on the street below 6000 RPM. Late style crankshaft bolt pattern.

[ Notice: ]Please refer to the 260 CID Engine detail section as well!

[ Thanks to for this information ]

Olds 307s come in a few varieties:

1980 - 1990: A VIN of "Y" indicates the standard 307, while a VIN of "9" indicates a performance 307. MAJOR difference, and easy way to verify 9 engine vs Y is that the Y engines have a thin, almost non existant harmonic balancer, while the 9 engines have a "normal" thickness balancer. Windowed main webs. In reality, however, you're not likely to blow out the bottom end of this motor on the street below 6000 RPM.

Roller-cam blocks, those with 7A heads, (some 1985's and all later 307's) use a larger diameter roller lifter (.921"). 5A heads have no roller lifter, 7A heads have the roller lifters. Later 307's also used a thicker pushrod; I don't know the years. Late style crankshaft bolt pattern.

1980 - 1984: "Y" motors, 5A heads, flat lifters, mild cam, single exhaust = 150 HP.
1985 - 1990: "Y" motor, 7A heads, roller lifters, mild cam, single exhaust = 140 HP, 255 ft/lbs torque.
1980 - 1985: "9" motors, 5A heads, .440 cam, dual exhausts = 180 HP, 235 ft/lbs torque.
1986 - 1990: "9" motors, 7A heads, roller lifters, .440 cam, dual exhausts = 170 HP, 245 ft/lbs torque.

[ Notice: ]Please refer to the 307 CID Engine detail section as well!

[ Thanks to Ed Atlee, Tom Lentz, Bruce D. Brumm, Jason Adcock, Paul Hartlieb, Daren, Bob Barry, Mike Rothe for this information ]

Olds 330s come in a few varieties:

1964 - 1967: Small combustion chambers, strong blocks, forged cranks. No EGR. '64 engines used heads utilizing shaft mounted rockers. 7/16" head bolts. Early style crankshaft bolt pattern.

[ Notice: ]Please refer to the 330 CID Engine detail section as well!

Olds 350s come in a few varieties:

1968 - 1972: Smaller combustion chambers, strong blocks, possibility of Nodular Iron cranks (a close second to the forged cranks that the 330's used). Four-speed 4-bbl engines had pretty decent camshafts. No EGR. Of course, if you get a W-31, you've got a pretty great engine right from the factory. The '68-'69 heads used a smaller exhaust valve than the later units. The high-compression pistons will make any of these a high-compression motor. 7/16" head bolts.

1973 - 1976: Larger combustion chambers, small intake and exhaust valves. EGR intakes, but the #8 heads were not too restrictive (compared to later units). Block is still relatively strong, with solid main webs. No more nodular iron crankshafts, but HEI ignitions on the later units are the best street setup. You need earlier heads to get high compression, even with high-compression pistons. 7/16" head bolts.

1977 - 1980: Large combustion chambers, small ports, EGR, low compression. They did, however, have ½" head bolts (in common with the 403's and diesel 350's), though the windowed mains on the block make these the weakest engines to start a performance rebuild from. In reality, however, you're not likely to blow out the bottom end of this motor on the street below 6000 RPM.

1977 to 1980 350's and all year 350 Diesels used ½" head bolts; all others used 7/16" head bolts. Thus the use of any other head requires reaming out the holes.

There were also the D- and DX-block diesel 350's that are the heaviest duty around, and which had ½" head bolts. These also used 3" mains while the gas 350's use 2.5" mains.

All use the late style crankshaft bolt pattern.

[ Notice: ]Please refer to the 350 CID Engine detail section as well!

[ Thanks to for this information ]

Olds 403s come in a few varieties:

1977 - 1979: Most, if not all have windowed main webs. It is rumored that a number of blocks have full main webs (no holes). In reality, however, you're not likely to blow out the bottom end of this motor on the street below 6000 RPM. Late style crankshaft bolt pattern.

The 403 has siamesed bores (making overheating in this area an issue), while all the other Olds blocks have water jackets between the bores.

403's used ½" head bolts; all others used 7/16" head bolts. Thus the use of any other head requires reaming out the holes.

[ Notice: ]Please refer to the 403 CID Engine detail section as well!

[ Thanks to for this information ]

Olds Diesels come in a few varieties:

Oldsmobile produced diesel engines in 4.3L 263 CID V-6, 260 CID V-8 and 350 CID V-8 variety. The 263 V-6 diesel was available in Cutlass Cieras and Supremes from 1982 to 1985. It was also available in Ninety Eight Regencys in '85. All Diesels were discontinued for '86.

According to my sales handbooks and literature, the 4.3 V6 Diesel was optional on all Cutlass Supreme, Supreme Brougham and Calais models in '82, '83 and '84. This was in addition to the 5.7 V8 Diesel. Option code for the 4.3 was LT6 and retail price was $500 (opposed to $700 for the 5.7). The 4.3 was not available in RWD Cutlass Cruiser models.

The initial 260 and 350 diesels were very bad engines as they were delivered. Definitly, one of the major problems was an uneducated public and GM's unwillingness to do anything early on. Most people didn't have a clue about diesels and neither did the mechanics. Most likely that, coupled with bad fuel, and water in the fuel, and bad head bolts did them in. Engines of the first few years have everything from alternator mounts breaking, injector pumps blowing seals, to top end problems with head gaskets blowing, push rods bending, to rockers breaking. Generally the problems are with head gaskets blowing and injection pumps rusting.

According to a number of sources, the newer diesel engines were like night and day compared to the original ones. After Olds worked out the problems, many owners have 200,000 - 400,000 miles on them, and they are still going strong. The 260 diesel apparently holds up better than the 350 though.

1978 - 1985: Diesel production continued until 1985 when all diesels were discontinued for the 1986 model year. Diesel parts were being handled by Detroit-Diesel-Allison, and not Oldsmobile. Both AC-Delco and GM Goodwrench rebuilt 350 diesel engines are available. In terms of rebuilding, try a competent diesel truck mechanic. Olds diesels were also used in Chevy trucks.

1979 - 1980: The Olds 260 CID V-8 diesel, produced from 1979-1980, with a whopping 90hp and 170 ft/lbs of torque, it made the 2.5L "Iron Duke" motor look like a W-30 by comparison. I wonder why you never hear about buildups based on a "diesel-block 260"? Perhaps the only engine whose main journal bores were larger than the piston bores! (well, very nearly)

1982 - 1985: The 263 V-6 diesel was available in the Cutlass Ciera and Supreme from 1982 to 1985, 85 hp, 4.057" and 3.385" stroke. Basically a 350 with two cylinders chopped off. The V-6 Diesel was an option in the newly designed and FWD 1985 98.

[ Notice: ]Please refer to the Diesel Engine detail section as well!

[ Thanks to Bob Barry, Joe Padavano, Steve Ochs, Greg Pruett, Tom Lentz, Kevin Wong, Lloyd, Paul Hartlieb, Thomas Martin, Kevin O'Brien, Dave Cullen for this information ]

[ Notice: ]Please refer to the Best Small Blocks section as well!

[ Notice: ]Please refer to the Blocks section as well!
[ Notice: ]Please refer to the Heads section as well!
[ Notice: ]Please refer to the Intake Manifolds section as well!
[ Notice: ]Please refer to the Exhaust Manifolds section as well!
[ Notice: ]Please refer to the Crankshafts section as well!
[ Notice: ]Please refer to the Pistons and Connecting Rods section as well!

Similarities: Other GM Engines

A Olds 350 is not a Buick 350 is not a Pontiac 350 is not a Chevy 350, is not a Cadillac 350, small and big block! This applies to Olds small block and big block engines. The only things in common with other GM division engines are the distributor cap, rotor, carb bolt pattern, and the transmission bolt pattern. Buick, Cadillac, Olds and Pontiac are the same, with five bolts. Chevy is different, with four bolts.

Chevy's are bigger and heavier than comparable CID Olds engines since they used very little nickel in the cast iron. Nickel is a expensive strengthening agent for cast iron. Low quality iron requires mass in order to make it stronger, which is why you will see the physical weight and size difference.

I hope you don't think that 4 bolt mains were put in Chevy engines so that they would be "Ultra-Strong" for the performance enthusiast. This is simply not true, they are there because the iron requires strength to keep the cap in place and 2 bolts in mush is not as good as 4 bolts in mush.

Oldsmobile blocks aren't made of mush, rather, they are made of high quality cast iron with plenty of nickel to make it strong. Olds big block engines were cast with extremely high nickel content until mid 1970. You can easily spot the difference in the shape of the "F" near the oil sending unit. Look at any 1968 1969 and early 1970 block and the F will be different in shape than any late 1970 to 1974 block. In 1975 the nickel content was lowered even more. Some of these later engines will have a mounting hole for a clutch swivel rod ball, some will not. This can always be machined.

As the weight of the engines go (stock engine weights):
Model Size Weight(lbs) Notes
Buick 455 600-640 (the later may be with accessories)
Cadillac 500 750
Chevy 350 535
Chevy 454 685
Olds 350 560
Olds 425 660 (flywheel, exhaust manifolds, cross over pipe, starter, water pump, alternater, carb, 5 quarts oil, distributer, etc.)
Olds 455 620
Pontiac 389 650 (a 455 should be the same weight)

And internal comparisons on bore, stoke and bearing sizes:
Maker Size Bore Stroke Mains Rods
Olds 455 4.126" 4.25" 3.00" 2.50"
Pontiac 455 4.152" 4.21" 3.00" 2.25"
Buick 455 4.312" 3.90" 3.25" 2.25"
Olds 350 4.057" 3.385" 2.50" 2.125"
Pontiac 350 3.876" 3.75" 3.00" 2.25"
Buick 350 3.80" 3.85" 3.00" 2.00"
Olds 400E 4.00" 3.975" 3.00" 2.50"
Olds 400L 3.87" 4.25" 3.00" 2.50"
Olds 403 4.351" 3.385" 2.50" 2.125"
Pontiac 400 4.121" 3.75" 3.00" 2.25"
Buick 400 ??? ??? 3.25" 2.25"

The Chevy 307 from the late 60s to early 70s is a real small block Chevy engine and not to be confused with the 307 Olds from the 80s, which is a real Oldsmobile engine and common to other small block Olds motors (260-307-330-350-403). The two are totally different in bore, stroke, bore spacing, block casting, head casting, etc. Nothing is interchangeable. Pontiac had a 301 engine in the late 70s-early 80s, which is a Pontiac engine, and somewhat common to other Pontiac engines (326-350-389-400-428).

The Buick, Olds and Pontiac 455s are two completely different designs with no interchangeable parts (everything but the carb and the distributor cap). The Buick 455 was a 1970 introduction, developed from the all-new Buick 430ci V-8 introduced in 1967 to replace the former "nailhead" 401/425 Buick V-8's that dated back to the fifties. The Pontiac was introduced in the same year, 1970, to replace the 428. That engine design, however, dates back to the original Pontiac V-8 introduced in 1954.

GM confuses people by first having each division build totally different engines with the same displacement (at least, after rounding off), such as the four different 350s, in the 60s, then mixing engines and divisions (such as the 305 Chevy used in Oldsmobiles, or the 403 Olds used in Buicks) when they started to pare down this overlap in the mid-70s.

Rules of thumb for GM engines:
Front distributor mounted at an angle = Buick engine.
Front distributor mounted straight up and down = Caddy engine.
Back distributor, intake separated from valley cover = Poncho (or 49-64 Olds).
Back distributor, passes through the intake manifold = Chebby.
Back distributor, does not pass through the intake manifold = Olds.

The real simple way to tell these late model GM engines apart is the following:

Olds (big and small block):

Chevy (small block):

1966-71 L6 (Chevrolet) engine
Codes are found on the right side of the engine block just to the rear of the distributor. This code has a letter designating the plant (Flint = F), a production date code (month/day), and a suffix code which identifies the engine.

Cadillac (big and small block):

Buick (big and small block):

1964-65 V6 (Buick) engines
The engine codes are found on the right-hand cylinder head. This code has a 2-letter prefix code followed by a 3-digit production code.

Pontiac (big and small block):

All Pontiac V8s (1955-1981) are basically the same size on the outside. Pontiac did not have a big block or small block. You will sometimes hear people refer to 421's, 428's, and 455's as big blocks. They are referring to the crank journals as these three engines had larger ones than the rest. The 400 was small journal.

[ Thanks to Fernando Proietto, Michael R. Hall, Tony Waldner, Joe Padavano, Doug Ahern, Bob Barry, Daren, David Whittemore, Chris Witt Brent Pinkstaff for this information ]

Engine Performance

The factory HP ratings of the 60's have as much credibility as . Keep in mind that the 70 W-30, which had a more radical cam and better flowing heads and intake than the W-34, was only rated at 370 HP. Mighty suspicious until you realize that GM Corporate mandated a 10 pound per HP minimum limit on all cars except the Corvette. The 442, to add to the conspiracy theory, had a curb weight of about 3700 lbs. Coincidence? I think not!

In fact, it's kind of hard to believe that all the W-30 equipment only raised the HP of the base 442 engine by 5-10 HP (do you really believe that the 66 W-30 setup didn't change the 360 HP rating of the L-69 tri-carb engine?). It is curious that the various year W-30 HP ratings were almost always 1/10 of the curb weight of the car for that year!

And, of course, the H/O was not subject to the GM 10 pound per HP limit (since it was theoretically built outside of Oldsmobile), so they were allowed to advertise 390 HP in the 68 H/O.

Year       Model     CID          CR     HP        Torque    0-60
'64        F-85      V-6                 165
                     330 2bbl      low   230
                     330 4bbl      hi    290
'64        442 4spd  330                 310                 7.4
'65        442 A2    400                 345                 7.8
           442 4spd  400                 345                 5.5
           Starfire  425 4bbl     10.5   370       470
           98        425 4bbl     10.25  360       470
           88        425 2bbl     10.25  310       450
'67        Toro      425 4bbl     10.5   385       480
           Starfire  425 4bbl     10.5   375       470
           98        425 4bbl     10.25  365       470
           88        425 2bbl     10.25  310       450
           88        425 2bbl      9.0   300       430
           Cutlass   330 4bbl     10.25  320       360
           Cutlass   330 4bbl      9.0   310       340
           Jetfire   330 2bbl     10.25  260       355
           Cutlass   330 2bbl      9.0   250       335
           442       400 4bbl     10.5   350       440
           T. C.     400 2bbl     10.5   300       425
'68        W-30      400 4bbl     10.5   [email protected]  [email protected]
           442 OAI   400 4bbl     10.5   [email protected]  [email protected]
           442 AT    400 4bbl     10.5   [email protected]  [email protected]
           T. C.     400 2bbl      9.0   [email protected]  [email protected]
'69                  350 2bbl      9.0
                     350 4bbl     10.25
                     400 4bbl     10.25
           88        455 2bbl      9.0   310
           88, 98    455 4bbl     10.25  365
           88        455 4bbl     10.25  390
'77 - '79  many      403 4bbl      8.5   175       310
'76 - '78  many      350 4bbl      8.5   160       275
'79        many      260 2bbl            105       205
'79        many      350 4bbl            160       275
'87 - '90  many      307                 140
'85 - '87  442, H/O  307 HO 4bbl         170       245
[ Thanks to Joe Padavano, Doug Ahern, Graham Stewart, Jeff Easton, Karl Aune, Bob Newbegin for this information ]

Cam Bank Angle, Lifter Size Considerations

Oldsmobile engines from 1964 onward originally used a 45 degree cam bank angle (CBA) and corresponding 0.842" diameter lifters. This angle is formed by the intersection between the cam centerline and perpendicular lifter centerline. By 1968, all Olds engines were using a 39 degree CBA and corresponding 0.842" diameter lifters. In the years between, 39 degree CBAs (and corresponding 0.921" diameter lifters) were used mainly on blocks found in models with premium engines, like Toronado's, 442's and Starfires. 45 degrees was being used everywhere else. The CBA also affects the pushrod hole angle in the heads.

The short story,

Before 1968, use this chart:
330  #1 coded block (64-67 ALL were 45 degree and had .841" lifters)
400  #B coded block (65 only 442, 45 degree and had .841" lifters)
400  #E coded block (66-67 442 39 degree and had .921" lifters)
425  #A coded block (65 only, 45 degree and had .841" lifters)
425  #D coded block (66-67 NON - Toro all were 45 degree and had .841" lifters)
425  #D coded block (66-67 Toro all were 39 degree and had .921" lifters

1968 and after, use this chart, as all are 39° and 0.841" lifters:
350  #2 coded block (68-7? ALL were 39 degree and had .841" lifters)
400  #G coded block (68-69 442, 39 degree and had .841" lifters)
455  #F coded block (68-76 ALL 39 degree and had .841" lifters)
And all 260, 307 and later 350 blocks.

The cam bank angle does not affect power output. The valves don't know the difference, as they just do what the tip of the rocker arm tells them to do; any differences in friction due to pushrod angles would be negligible.

There are a couple of ways to check for cam bank angle, and if it is a Toro 425 block (probably applys to all blocks):

Basically, the way it worked out was that if the early (pre 1968) big block had 0.921 lifters, it was an advanced [for the time] 39-degree block, and if it had the normal 0.842 lifters, it was an old 45 degree block.

Anyhow, the presence of the drill spot on a pre-1968 big block means a 39 degree block and heads. Easy to spot, too.


[ Notice: ]Please refer to the Engine Rebuilding Cam Bank Angle section for more information!

[ Thanks to Jim Chermack, Chris Witt, Bob Barry for this information ]

Experimental 455 Engines

Aluminum 2 Valve 455

The aluminum Can-Am motor you are refering to is actually an aluminum version of the pushrod 455 block and heads! The motor was used in the McKee Can-Am cars of the 60s (one of which was sponsored by the Smothers Brothers, who also sponsored a series of 442 Super Stock class drag cars in the late 60s).

The Smothers Brothers Can-Am car was actually offered for sale in the March 96 Hemmings, complete with the aluminum Olds motor for $125K. The twin-turbo injected 455 on display at the REO museum is, I believe, one of these Can-Am motors (note that it is NOT a DOHC motor).

Aluminum DOHC 4 Valve 455

There was also a Can-Am all aluminum engine which had double overhead cams and was a very serious engine; huge port area for serious breathing. The DOHC version was intended as an all-out drag and marine race engine. It was all-aluminum and used a gear drive for the cams. For a very nice article on these engines, track down a copy of the May 1971 Hot Rod.

Aluminum 2 Valve Turbo 455

The twin-turbo injected 455 on display at the REO museum is, I believe, one of the Can-Am (see "Aluminum 2 Valve 455" in this section) motors (note that it is NOT a DOHC motor).

Iron, Aluminum 2 Valve 455 Hemi (W-45)

The W-45 was an experimental engine that Olds developed to compete with the Chrysler Hemi. It was a overhead cam of some sort. The engine (pushrod version) was developed in the mid-60s for anticipated introduction in 1970, but was killed in late 1967 as a result of the coming emissions controls and the insurance industry putting the screws to muscle cars. There were some cars installed with this engine for testing.

The cast iron version (with aluminum heads) that was meant to be the production engine (W-43) has true pushrod hemi heads. The block is different from the standard ones in that the camshaft was raised higher than normal to give the proper pushrod angle to the heads and cam (which would have also had to have been different because of a different bank angle). This explains the rounded top of the timing cover.

The pushrod version had a raised cam, to improve the pushrod angle as a result of a lot of bent parts early in the development program. The block actually had a dummy camshaft in the normal position to drive the distributor and oil pump, with a separate, bolted-in cam carrier in the raised position for the real cam. The block had 4 bolt mains as well.

Iron 4 valve 455 Hemi (W-43)

There was also an engine coded W-43 in 1969 to 1970, though it was never offered as a production unit. It was a four valve per cylinder 455 CID engine. It was developed in 1969 and 1970 by John Beltz, Lloyd Gill, Joe Jones, and Frank Ball. It was rated at 500 to 550 hp at 6500 rpm with a single Rochester Quadrajet on an aluminum manifold. It was constructed with a cast iron block and heads as well as an aluminum block and heads, which shaved 75 pounds of the 455 CID production engine weight. The engine had narrow valve angles for super-efficient combustion chamber design, central spark plugs and could be adapted for chain or gear driven overhead camshafts.

The 455-inch-configuration block has 4.625-inch cylinder centers, 4.125-inch bore and 4.250-inch stroke. Making use of 3.00-inch main bearings and 2.50-inch rod journals, the engine was fitted with a specially-prepared cast crank fitted with SAE-1140 forged steel rods, forged 10.20-to-1 pistons and riding on Morraine 400 bearings. The four-bolt-main block boasts two additional 5/8 inch oil drain holes.

Topping off this unique engine is a pair of four-valve heads with 1.750-inch intake valves (SAE-8460 steel) with 22-degree stems and 1.375-inch exhausts (214-N stainless steel) with 15-degree stems. Special Stellite seats, bronze-alloy guides, o-ringed plug tubes, 14-mm spark plugs, 3/8-inch pushrods, and aluminum rocker arms complete the head treatment.

Aluminum 4 valve 455 Hemi (OW-43)

There was an experimental engine based on the W-43, coded OW-43. It was designed for road racing applications. It had the same basic configuration as the W-43, but the materials were different. The block was cast from Reynolds-356 alloy and fitted with pressed in dry steel cylinder liners for the forged 12.2 to 1 pistons. It used billet steel connecting rods and a machined forged steel crank.

The OW-43 was developed at the same time that Chevrolet released its all aluminum ZL-1 427 engine, but the Olds engine was far more advanced and exotic than the Chevrolet engine. It had a redline just under 8500 rpm, and put out 300 HP at 3000 rpm, and 600 HP at 6000 rpm. The top output recorded for this engine at the Lansing dyno facility was 700 REAL horsepower at 6800 rpm. Tests were run with both carburetion (four Weber 48-IDA two barrels) and injection (three-inch ram stacks), with injection showing the most potential over 6000 rpm.

[ Thanks to Joe Padavano, Dave Paulison for this information ]

Engines 1995 - Present

This is the Aurora DOHC V-8 engine, the A8. [ Aurora Engine ] The words "Manufactured by General Motors exclusively for Oldsmobile" appear on the intake manifold's tuned runners.


CID    Years      Bore   Stroke  VIN  Color  Notes
4.0L   '95 -      87mm   84mm                A '95 introduced in '94.

Engine Performance

Year  CID          CR       HP        Torque
'95   244 (4.0L)   10.3:1   [email protected]

Indy Car Engine

Production Aurora V-8 Indy Aurora V-8
Displacement 4.0 liters (244ci) 4.0 liters (244ci)
Cylinder Angle
90 degrees 90 degrees
Cylinder Bore Spacing
102mm 102mm
Dual overhead cams Dual overhead cams
Valves per Cylinder
4 4
Camshaft Drive
Cylinder Head Material
Cylinder Case Material
Cylinder Liners
"Dry" iron"Dry" iron
Crankshaft Design
90 degrees90 degrees
Fuel System
Sequential EFISequential EFI
Engine Controller
Delco ElectronicsDelco Electronics
Maximum rpm
250hp @ 5600 rpm600+ hp
Unleaded gasolineMethanol
Bore Diameter
Crankshaft Stroke
Deck Height
Compression Ratio
Throttle System
Throttle BodyIndividual Runner
Lubrication System
Wet SumpDry Sump

The Aurora will have white diamond metallic paint with black and gold highlights (sounds like the performance colors of about 28 yrs. ago) with Indy 500 graphics. A power sunroof, 3.71:1 transaxle ratio (included with the Aurora's optional Autobahn package), chrome plated aluminum alloy wheels and Goodyear Eagle P235/60R16 tires rated for sustained 150 mph speed. The non-stock items that will be installed are those mandated by USAC which include a roll bar and a five-point safety harness for the driver and passenger.

[ Thanks to Glenn for this information ]

Drag Race Competition Engine (DRCE)

The Olds DRCE, as raced by Warren Johnson is basically a set of Olds block and head castings designed to accept big block Chevy internals. One interesting note is that it uses a BOP bellhousing bolt pattern instead of the Chevy bolt pattern. Front cover and water pump interface is Chebby, however.

Olds tried to ensure that all the shortcomings of the Chebby motor were eliminated in this new design. The block was designed to accept up to a 650 cu in displacement. Heads are unique and, interestingly, use ten valve cover bolts per side, just like "real" Olds motors. Note that since Olds has dropped out of NHRA racing sponsorship and Pontiac has become the body style of choice in Pro Stock (due, in no small part, to Pontiac contingency money replacing the Olds contingency money), the DRCE II is now a "Pontiac" motor.

[ Thanks to Joe Padavano for this information ]

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