Exhaust Manifolds

* 1949 - 1964 * 1964 - 1990 * 1995 - Present * Exhaust General

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

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. ]

Exhaust Manifolds 1949 - 1964


Casting numbers are just on the manifold - I can't remember if there is any RH or LH information.

Year         ID/    Casting
Used         Code   Number    Application
                    568677    LH; 371 CID.
                    568926    RH; 371 CID.
1960                573325    LH; 394 CID. 98.
[ Thanks to Scott Clark for this information. ]


Dual Exhaust Manifolds
At least for 371 dual exhaust manifolds, the only thing that made them dual exhuast was a factory cast block off for the right side manifold.

371 - 394 Manifold Differences
I measured the ports on both a LH 394, and 371 exhaust manifold. Here's the results (all are approximate):
CID, Casting #s Outside ports Center ports
371 (568677, 568926) 1.5" x 1.5" 2.5" x 1.5"
394 (573325) 1.5" x 1.75" 3.0" x 2.0"

So, the ports really do have some serious differences in size (particuarly the center port).

There is also some sort of dimensional difference between the two manifolds, since the one from the 371 won't even bolt to a 394 head (head studs won't line up with the slots in the manifold). Assuming a somewhat proportional difference in intake ports, it's easy to see why a J-2 manifold would never fit a 394.

[ Thanks to Scott Clark for this information. ]

Exhaust Manifolds 1964 - 1990

The 1969-72 exhaust manifolds feature a divider between the center exhaust ports. The 1967 and earlier models do not have this feature. Also, all manifolds except 1970 to 1972 will have a heat riser (shutoff) on the left-side exhaust manifold.

All Olds small-blocks with dual exhausts used the single-exhaust right-hand manifold, with one opening capped off. There are no true dual exhaust small block manifolds.

[ Thanks to Kevin Hoopingarner, Bob Barry for this information ]


The cast-in ID consists of a large [1"] letter or number, usually found at the front, over the front exhaust port. On earlier units, it can be found over the REAR exhaust port. There is also a 6-digit casting ID, usually somewhere near the center.

As per convention, if the big single-character ID is a number rather than a letter, that denotes a small block part. It was not uncommon, especially after 1970, for small block exhaust manifolds, such as 1 and 4 or 5, to be used on big block cars. Sometimes you can find dual exhaust manifolds on big cars, too.

Exhaust manifolds come in many styles, we'll cover the most popular. The main difference for the performance enthusiast is whether the center ports are divided in the manifold, as in the late W and Z units. LH= for left hand side, RH= for right hand side of engine.

D, E, G, H, J, K?- Toronado exhaust manifolds. Duals. They typically turn up and out at the outlet, far more so than those for any other car. Since that would run the exhaust into the frame or body of most cars, these are useful mainly for identifying a Toronado engine.

A number of sources have pointed out that there is no difference between W-30 and 442 exhaust manifolds. An article in JWO explained confirmed this.

NOTE: The W 389268 was not used on the 68 442 as stated in the Supercars book and other places. The 68 uses a unique manifold (Y-398706) with heat shield.

[ Thanks to Chris Witt, Ed Ekstrom, Dan Williams for this information ]

Year         ID/    Casting
Used         Code   Number    Application
'65 - '68      X    389269    LH; Cutlass, 442.
               W    389268    RH; Cutlass, 442.
'67 - '69      A    384785    LH; full size. 425.
               T    39870934  RH; full size. 425.
'68                           Cutlass: early 1968 models use same as 1967.
                              Cutlass: late 1968 models use same as 1969.
'68            T    398708    RH; big block
               X    389269    LH; Cutlass, 442, some VC and SX.
                    398705    LH; Toro
'68            Y    398706    RH; Cutlass, 442, some VC and SX. Ribbed for heat shield.
               R              LH; full size.
'68 - '70      S    384895    LH; full size. With heat shield to protect
                              steering box.
'66 - '70      S    393233    LH; full size. With heat shield to protect
                              steering box.
'69 - '74      W    402295    LH; Cutlass, 442, W-30, H/O.
'69 - '72      Z    402294    RH; Cutlass, 442, W-30, H/O.
????           X    406301    ????
'70 - '??      X    412287    LH: full size, Cutlass.
'73 - '74      X    412287    LH: 442, W-30.
??             H    411970    RH; Toro.
??             J    407103    LH; Toro.

'63 - '70      1    380001    LH; X-over. 350.
??             1    411961    LH; No X-over. Straight down. 307, 350 gas, 350 diesel.
??             1    411981    LH; 350 gas.
'65            2    380145    LH; 330.
'66 - ??       3    381921    RH; X-over.
'66            4    398704    RH; 330. Standard issue manifold.
'68 - '73      5    398704    RH; X-over. 350. Delta 88.
??             8    558319    With "Z-Y" underneath the "8".
??             8    558480    With "H-Y" underneath the "8".
'65           12    561796    RH; Single outlet - only SB true dual exhaust manifold.
??                  581798
'81-85        14    22503678  LH; 260, 307. 86, 87 442.
'81-85        17    2506300   RH; 260, 307. 86, 87 442. O2 sensor boss.
??             3    563619    RH; 350 diesel. Gas also?
'86-'90       None  None      RH, LH. Stainless steel tubular manifolds found on
                              7A head 307's.
[ Thanks to Chris Witt, Kevin Hoopingarner, Mark Prince, Kevin O'Brien, Matt Cremean, Bill Reilly, Dan Williams, John Pajak, Tony Williamson for this information ]


ID Casting # Side
A 384785 LH
Used on big cars about 1967 to 1969. Single outlet is straight down in the center, not good for an A-body car. Companion to T, typically.

H 411970 RH

J 407103 LH

Used on big cars. ## holes?, exit angle? Might fit in A-bodied cars, with effort. Companion to T, typically.

T 3987094 RH
Used on big cars about '67-'69. Two holes; one for crossover pipe from the LH side. Main outlet has 2-bolt flange angled about 45 degrees down and back. Might fit in A-bodied cars, with effort. Companion to A, typically.

W 389268 RH
1965-67, A-body with big block and dual exhaust. This one has the W over the rear runner. Does NOT have a divider between center ports. One 2.5" outlet, 2-bolt flange, points about straight down. Companion to X-389269-LH. See also Y-389268-RH [?]

W 402295 LH
1969-72 442, W-30, H/O, A-body with big block and dual exhaust. "W" is over the front runner. THE most desirable set to have. Has divider between center ports. One 2.5" outlet, 2-bolt flange, points about straight down. Companion to Z-402294-RH.

X 389269 LH
1965-68 442, A-body, some Vista Cruiser and SX's with big block and dual exhaust. This one has the W over the *rear* runner. Does NOT have a divider between center ports. One 2.5" outlet, 2-bolt flange, points about straight down. Companion to W-389268-RH.

X 412287 LH
1970-up? A-, B-, C-body with big block and dual exhaust. Has the divider between center ports. One 2.5" outlet, 2-bolt flange, points about straight down. Good substitute for W-402295-LH.

X 412287 LH
1973-74 442, W-30 with big block and dual exhaust. Has the divider between center ports. One 2.5" outlet, 2-bolt flange, points about straight down. Good substitute for W-402295-LH.

Y 398706 RH
1968 442's, A-body, some Vista Cruiser and SX's with big block and dual exhaust. This one has the Y over the front runner. Does NOT have a divider between center ports. One 2.5" outlet, 2-bolt flange, points about straight down. The manifold has raised ridges in it and a heat sheild that rests on them. Companion to X-389269-LH.

Z 402294 RH
1969-74 442, W-30, H/O, A-body with big block and dual exhaust. THE most desirable set to have. Has divider between center ports. One 2.5" outlet, 2-bolt flange, points about straight down. Companion to LH unit W-402295 LH.

1 411961
Small block standard issue LH manifold. ?? about divider. ?? about outlet size, 2-bolt flange, points about straight down. Companion to RH unit 4-398704 unit.

Small block standard issue RH manifold. ?? about divider. ?? about outlet size, 2-bolt flange, points about straight down. Companion to LH unit 1-411961.

12 561796 RH
Early 330 small block. ?? about divider. ?? about outlet size. Single outlet dual exhaust sb manifold.

14 22503678 LH
1981 260, 1981-1986 307 small block with single exhaust. ?? about divider. ?? about outlet size, 3-bolt flange, points about straight down. Companion to RH unit 17-2506300.

17 2506300 RH
1981 260, 1981-1986 307 small block with single exhaust. ?? about divider. ?? about outlet size, 3-bolt flange, points about straight down. Shares the same basic casting as the earlier 350/403 manifold, and have provision for an O2 sensor. Companion to LH unit 14-22503678. Also used with LH unit 1.

Tubular Tubular RH, LH
Stainless steel 7a head 307 exhaust manifolds. Welded. You cannot miss them, they look nothing alike. The tubular stainless steel looks like someone took exhaust pipe and welded some port flanges to it. These will be dull and somewhat smooth, but very different than cast iron manifolds. Easy to spot. They equire a gasket, which differs from cast iron which does not.

Typical exhaust manifold pairs, left/right, are: X/W, X/Y, W/Z, A/T, R/T, R/S, D/E, G/H, J/K, 1/4, 1/5, 1/17, 14/17

On the subject of 350 exhaust manifolds, there are some slight differences. The 350 diesel manifolds on the trucks came with no block off plate on the passenger side. They use a different sealing system than the regular gas manifolds found on the cars. The 350 diesel cars used the same manifolds as the gas engines with the block off plate. There was also a change in the mid 70's with the different sealing system requiring an exhaust doughnut to be installed to make the sealing flange. The earlier ones had this cast into them. W-31's used STANDARD 350 exhaust manifolds with the block off plate.

[ Thanks to Chris Witt, Ed Ekstrom, Dan Williams, Mark Prince, Thomas Martin, Bill Reilly, Jim Chermack, Steve Ochs for this information ]

Exhaust Manifolds 1995 - Present




Cheap Dual Exhaust

For any who can't spring for headers right off, this idea may also be helpful. 1) Take off the cross-over pipe. 2) Cut the end that goes to the drivers side manifold off and, using a hammer & vice, crush down the pipe coming off of it (make sure you leave enough pipe attached to the end to do this). Then take this piece and have its crushed seam welded at a local station (5 bucks). The result is a plug that can be used where the crossover used to connect with the drivers side manifold. Then just run a second exhaust pipe back from the passanger side manifold (buy and have shaped at an off-brand muffler shop, very cheap) where the crossover used to connect. Add the muffler of your choice and wala, dual exhaust on the cheap, and ya get to talk about how ya kept stock exhaust manifolds.

[ Thanks to Michael for this information ]

Dual Exhaust In General

Carb Signal
When you open up the exhaust, you change the metering signal seen at the carb, it tends to run leaner, so you must richen it up to maintain proper mixture. (jet/rods). A competent tuner can open up the exhaust, retune, and make the car have potentially better emissions than when the car was certified by the EPA. And you may need to monitor how the EGR is, if it is a Neg or Pos backpressure type, you may need to go to a Port type. Or tweak WHEN the EGR applies.

Exhaust Sizing
With the on again/off again discussion of how much exhaust is enough/too much/not enough, it got me thinking, so I did some research. Take it for what it's worth, and do what you want with it. Just thought I'd share what I learned.

Engine HP x 2.2 = Loss free air flow capacity needed for single muffler system. For Duals, divide the single system number by 2 to determine loss free air flow capacity needed for each muffler.

Determining Necessary Exhaust Flow:
Example: 300 hp x 2.2 = 660 SCFM* for single OR 330 SCFM for Duals.
* SCFM = Standard Cubic Feet per Minute
Based on Dynomax Racing Series Mufflers:
2¼" inside dia. both ends, oval muffler, 19" overall length, 323 SCFM for Duals and 646 SCFM for single.
2½" inside both ends, oval muffler, 19" overall, 515 SCFM for Duals, 1030 SCFM for single.
3" inside both ends, oval muffler, 19" overall, 1000 SCFM for Duals, 2000 SCFM for single.
Based on Dynomax Street Series UltraFlow Universal Mufflers:
2" inside, oval muffler, 19" overall, 318 SCFM for Duals, 636 SCFM for single.
2¼" inside, oval muffler, 19" overall, 455 (cool!) SCFM Duals, 910 single.
2½" inside, oval muffler, 19" overall, 489 SCFM Duals, 978 SCFM single.

If anyone has questions I might be able to answer, or is interested in Dynomax part numbers, to go to the local parts store to purchase, or cross over into another make, feel free to email me direct. I'll get back to you as soon as I can.

1 3" vs. 2 2" Pipes
With a few notable exceptions, virtually all cars built since catalytic converters were introduced in 1975 have had only one catalytic convertor regardless of whether the car has single or dual mufflers. This is not necessarily a bad thing if the plumbing is up to the task (and, at least on the earlier cars, it usually _wasn't). Keep in mind that a single 3" diameter pipe has more cross sectional area than two 2" pipes. Of course, this is a very simplistic view, as the effects of kinking at bends, flow velocity, and other elements must be considered. For example, a large diameter tube which has been flattened into an oval for ground clearance (whether intentionally or not) will have less cross sectional area than the same tube in it's circular configuration.

Of course, all of this assumes the catcon has flow characteristics to match the rest of the system. As I mentioned earlier, it often does not. Assuming one is installed which does have sufficient flow rate, consider the 2-into-1-into-2 exhaust system as a factory "H" pipe design (which, in reality, it is). Every exhaust pulse sees both mufflers, which has the same backpressure reducing advantages here as it does in any exhaust system.

[ Thanks to Angel Castrodad, Stephani, Joe Padavano for this information ]

Dual Exhaust 73-77 Cutlass

I ordered the Flowmaster 2.5" exhaust system from Summit. I should have just flushed $200 down the drain. On my 75 Cutlass, there simply is not enough room for exhaust pipe of this size. They WILL hit the springs or the upper arms. The catalog says 67-77 A-bodied cars. I believe they will fit most cars up to 72, but the 73-77 cars are just too tight. The box says 67-73 A-body. The pipes had stickers that said 67-72 Chevelle. Gack! By the time the exhaust shops (2) played around with the mess, I finally came to realize that it just wouldn't work. That's what the exhaust shop guys had said all along. Yes these were custom exhaust shops. Finally after many hours and much $$$$, I had another shop custom bend a set of 2.25" pipes that fit beautifully. Oh, and yes, I do have a double hump crossmember from a 73 Cutlass. The problem is from the mufflers back. I suggest that members with this series car save your money and have a custom exhaust shop MAKE you a set of pipes in 2.25".

I don't know about the Flowmaster setup, but I just examined a '77 442 that had a custom 3" true dual setup installed, with both tailpipes up and over the axle in stock positions, using the same '73 442 double hump crossmember that I have. He also, however, had just installed new HD springs in all four corners in consideration of swapping in the '68 455 BB. Maybe your back springs are a bit on the soft side? Dunno, but I do know that if a 3" has been done, a 2 1/2" can be done, somehow.

[ Thanks to Ed Binnix, Michael A. Evans for this information ]

Dual Exhaust Using Crossover Exhaust Manifolds

All 1964 to 1972 small blocks used the same exhaust manifolds for dual and single exhaust applications. Only the big block cars used different manifolds. There wasn't even a separate one for the W-31's. The small block exhaust manifold used a cover plate over the crossover outlet for dual exhausts. There is no small block dual exhaust manifold.

Find a muffler shop that will cap the extra outlet on a crossover type manifold. It might take a while to find a shop that will do it, and do it right.

Have a muffler shop bend some pipe (preferrably aluminized for durability) to go under the oil pan (like a regular exhaust crossover pipe), and out toward the back of the car, sort of parallel to the existing single exhaust pipe.

Running the pipe, from the driver side, under the transmission crossmember, requires a little denting of the pipe. It will look and work just fine. If you are concerned about a small amount of ground clearance and under car looks, you might cut and weld in an arch to except duals.

Crossover Outlet Cover Plate

The crossover outlet cover placte part is officially called "Cap, Right Exhaust Manifold Cover", part number 386498, used from 1965 to 1971. In 1972, this became part number 382636, as listed in the 1972 assembly manual as "cap - N10 only". N10 was the dual exhaust code option. These parts have been since discontinued by GM.

As a source, try a GMC or Chevy truck dealership. The 5.7 diesels in these trucks ran duals with the same manifolds that cars used. They also had these caps on the RH manifold. This also means that Detroit-Diesel-Allison is a place to look, because they took over supporting the Olds diesel.

Making a Crossover Outlet Cover Plate

There are flanges that hold the exhaust head pipes up to the dumps on exhaust manifolds on any car, right... The exhaust head pipe passes through this flange. The flange forces the flared end of the head pipe against a doughnut gasket forming a seal with the dump on the exhaust manifold. Ok, any muffler shop should be able to provide you with one of these flanges.

Have your local welding shop weld a round piece of steel over the hole in the head pipe flange (where the head pipe would pass through. Presto, you have your cap. Then use an exhaust doughnut gasket between your new cap and the crossover outlet, bolt it up and you are done.

The muffler shop offered to cut the cross over pipe and weld the crimped end. For a much cleaner installation I chose to fabricate a cap. I went to the local auto parts store and bought a new cross over pipe. I then cut the pipe about two inches from the end. I took this piece to a local metal working shop. They turned down a piece of 2" bar stock on a lathe to the inside diameter of the pipe, pressed it in and welded it together. This makes for a much cleaner installation and besides no exhaust gas is going to burn through 1" bar stock.

[ Thanks to Stephen Hoover, Glenn, Jim Chermack, Art Fuller, Graham Stewart, Paul Hartlieb, Tony Waldner, Cliff Feiler, John Gene for this information ]

Dual Exhaust in G-body Cutlass

Using Early Dual Hump Transmission Crossmember
G-bodies used an offset cross member that only has a single hump. A dual hump crossmember from a late 1960's early 1970's Cutlass, Skylark, Monte Carlo, Chevelle, Lemans, etc. will work great if you remove 1-1¼" from both sides. This is required because the earlier car are slighty wider than the 1978 to 1987 G-bodies. You do have to make some modifications to make it work, but in my opinion, it is definetly worth the effort. A Sawzall or reciprocating saw is best to do the modifications.

The cross member will have to sit on the bottom of the frame rails instead of on top, but it will work just right for where the headers dump. You might also need to do some work to the lower frame rail on the passenger side. Also had to remove the support for the original crossmember located on the pass. side of the frame. Four new bolt holes in the frame rail, and you are in business.

As mentioned earlier, the orignal crossmember is offset, and the dual one is straight. Therefore, the new one will not fit in the original one's location. Also, it will have to sit on the bottom of the frame rail instead of the top. There is not enough room between the top frame rail and the floor for the dual one to sit. You would really have to MODIFY the floor in order for the crossmember to fit on the top frame rail. I would not be hesitant about this! Yes, you might think that there is not enough strength in this spot. But it could easily be reinforced with angle iron or box steel. I just have mine bolted to the bottom rail with nothing extra added and nothing has twisted or bent. I DO plan on strengthing it in the near future though.

The next thing you have to do is obtain your proper pinion angle. In other words, make sure that the transmission is sitting at the same level it was originally. You can use shims, etc, to obtain the proper level. you will also need a new method of support for the rear of the tranny. I made a block of steel about 3" tall to make up for the difference.

Both Pipes Routed Under Single Crossmember Hump
My '84 Cutlass (350 4bbl.) has duals and the original V-6 crossmember. The duals fit just fine. They come down and then both pipes go to the passenger side of the car, and run alongside each other to the back where they are run to their specific sides. Any good muffler shop should be able to do this. I've seen plenty of other's (mostly Cutlass) done the same way. I have (I think) 2" pipe all the way back, but my friend has larger on his Cutlass. When the pipes are run alongside each other, they shouldn't be touching each other, but should be about 5 inches or so apart. This also makes it easy to install an equalizing (H) pipe if you want to.

I have seen a somewhat different steup than the dual-hump or cross-over pipes. I recently saw a Cutlass GT with true dual but with a single hump crossmember. How did he do it? Well, he installed the reducer to the collector and welded a 90 degree mandrel bend to it. He passed the pipe under the oil pan (he had a heat shield made so not to heat the oil too much) and made another 90 degree bend right before joining with the pass. side tube and ran both pipes under the original, single hump. From there on it was installed like the factory setup. He got excellent clearence and no ugly tubes showing. Real clean.

Using Ford Crossmember
If you don't mind running a Ford part, you can pick-up a junkyard tranny cross-member from mid-80's mid-size Fords which:
1) Will slide in easily between the frame-rails of the 80's regal frame without cutting.
2) Will allow the use of dual exhaust because most have two "humps" already.
3) Will let you use a "normal" THM-400 center-mounting style rear tranny mount, and,
4) Is slightly lighter in weight (an issue to some and not for others) and strong enough (IMO).
5) Works for small block and big blocks.

Once you slide the cross-member in between the frame-rails, attach the tranny/mount to it, making sure the cross-member is where you like or need it. Then its only a matter of drilling 4 easy holes, two in each lower frame-rail and into the cross-member. Tthere are big ¾" holes on each end of the cross-member for the Ford frame mounting system so just make sure you drill through the frame at a location which will end up also drilling new holes through some good useful meat of the cross-member.

Insert your bolts, lock washers, and nuts and that's it. It took me longer to get the grease off the cross-member than it did to install.

[ Thanks to Tom Millard, Clayton Pierce, Angel Castrodad, Al Varhus, Trevor Lee for this information ]

Dual Exhaust Using Toronado Manifolds

I have noticed several posts regarding exhaust manifolds for small block Oldsmobiles. We went looking for some help in this area in 1994 when we were racing our 71 Cutlass 'S' in the Street Stock division at our local asphalt short tracks. We eventually found that we could use the passenger side manifold off of a late 70's Toronado (probably with a 403, but I bet they're all the same in those years) on our car.

It doesn't have a crossover and points back at the same angle as the firewall does down there. It does have a kink in it that goes over the oil filter adapter, but it seemed better than the usual stock small-block unit.

Speaking of the oil filter adapter, you will need to get that with the manifold, as this design will not work with the typical one. We ended up using one from a donor 425 Toronado engine we got from a friend, and it fit just right. And you will find that the large diameter oil filter won't work, but the one for later model Olds diesels will. If you're going to go with a remote filter, then you'll have no trouble.

The Toronado/Seville/Eldorado FWD oil filter adapter takes a different gasket. The center web is shaped like a lazy J instead of a lazy S. It's steel and not available in the parts stores I check at. I got it from the dealer under P/N: 563450. Failing that, just clean reuse the old steel gasket with some Permatex Hylomar or Fel Pro Blue on it.

[ Thanks to Ken Snyder, Scott Woodworth for this information ]

Exhaust "H" Pipe

The H cross over pipe, sometimes called an equilizer by muffler shops, is definitely good. It's effects were to lower peak horsepower just a bit (like 5 out of 400 that they had) and raise torque by just a bit (like 10ft/lbs). It lowered peak hp by a few hundred RPM (their test engine was a really hi-revving big block) and peak torque by a few RPM too. It mellowed out the exhaust tone and will probably increase exhaust system lifespan.

The H-pipe (crossover) equalizes the exhaust flow going out the exhaust. It also takes the harshness out of the tone. It does restrict exhaust back pressure, hence the 2 1/2 pipe. Reduction of back pressure equals more useable horsepower. Things to take into consideration are compression, horsepower at what RPM, torque at what horsepower. All I know for sure is, that for this to work correctly, the h-pipe should be as close to the headers as possible. Sometimes this will restrict transmission removeal, and/or starter removal. Since most of the time when you pull a engine or transmission, you generally drop the exhaust, so I never worried too much about it. If you do the crossover and you don't like it, you can always remove it.

The H-pipe should be placed as far forward as possible where the exhaust is hot (like right behind the header collectors). Spray the pipe with white paint and take the car for a run to find that hot spot.

Installation: Have shop weld flanges on each end of mufflers and pipes that connect to mufflers, along with center of crossover to allow removal of system very easy. Makes for better sealing also vs. U clamps.

[ Thanks to Lisa Madsen, Peter Slisz, Rob Thomas for this information ]

Full Size Dual Exhaust

On my 76 98 I had a local muffler shop run dual 2.5" pipes under the crossmember on the passenger side since it is a single hump trans crossmember design. They both fit under it together with no problem. The shop just bent the driver side back over where it belongs after crossing under. I'm sure this hurts flow a little, but it was alot easier than trying to find the right crossmember and swapping it out.

A rather cheap alternative to the diesel pipe is the dynomax 2.5" mandrel bent exhaust system for the '94-'96 Impala SS. Fully aluminized, it'll fit a C body like a glove and will fit a B body with minimal work. The pipe to the catalyst will have to be formed, due to the location of the catalyst on the Impala being VERY far forward. I lucked out, I already had a 2.5" mandrel bent S turn (very gentle one) which lined up almost perfectly with the pipe. The pipe(s) cost me only $70, and I have friends with a muffler shop, which brought the total cost to under $200. A tailpipe had to be constructed, due to the Dynomax system utilizing a resonator after the over-the-axle pipe. A turbo muffler was utilized. Drones like crazy above 2000 rpm, but smoothes out after around 2500 rpm (I never take the motor over 4000 rpm due to the 2.41 gearing in my '78).

[ Thanks to Dan Dale, Mike Jones for this information ]

G-body 442 Exhaust

I highly recommend the factory 442 exhaust system. The mufflers are very small (free-flowing) and are actually called resonators in the service manual.

It will connect to any '83 or later Cutlass with Vin 9 or Y engine. You will need the tailpipe hangers also to convert to dual exhaust. The price is reasonable for an aluminized factory exhaust.

As a daily driver, this system is good for about 6 years, for a car not driven in salt like mine, it is good for about 12-14 years. My '87 442 still as original exhaust on after 60,000 miles.

This is the best sounding factory small block exhaust I have heard on a car since the mid-70's. The tone is mellow but the rumble tells everyone it is a V-8. The sound is much better than a Monte-Carlo SS (my friend has tried 3 exhaust systems Walker, Flowmaster, and factory, on his '86 SS and still likes mine better).

22526205  Left hand muffler/tailpipe assy. List $125  Cost $93.75
22526204  Right hand muffler/tailpipe assy. List $125  Cost $93.75
25516189  Intermediate Y-pipe behind conv. List $ 89  Cost $66.94
22520309  Left hand tailpipe hanger assy.  List $ 21  Cost $15.83
22520308  Right hand tailpipe hanger assy. List $ 21  Cost $15.34
[ Thanks to for this information ]


You may think headers are worth the trouble for a street engine, but I don't think so. But hey, each to his own. I will open mine up at the strip once in a while this year. If it wasn't for that I would have installed the manifolds. It can be tough to hear your car when racing someone with open headers. I bought the Ultra-Seal gaskets for the header to head connection and Uni-Seal donuts for the header to exhaust. I hope to reduce the maintenence on these two items. As far as re-tightening goes, it is a ritual when checking the oil.

Yes, ground clearance is reduced. Yes, you will scrape when you pull a Dukes of Hazzard. Yes, you will have to periodically tighten the bolts and replace the collector gaskets. You also have to check the oil and change it every so often, tune the car up, and perform other routine maintenance. I've never had any problems changing the oil filter (except for the fact that the primary tubes run directly under the dripping filter fitting, resulting in a few seconds of oil smoke upon startup).

Yes, you need to remove the oil filter adapter when installing the headers, but not when just changing the filter (at least, not with the headers I've used). Yes, you will need to drop the starter to install the headers. And I will admit that the latest set (second generation Kenne-Bell) don't clear the clutch linkage as well as I would like. But, come on. There is no way that the stock manifolds (W/Z notwithstanding) will flow as well as headers. It's just a part of the cost of playing the game.

By the way, I've found two coatings which work very well on headers. Aluminum sprayed headers work very well on a daily driver. The aluminum coating is somewhat forgiving to being knicked, and looks good even when oil is spilled on it. Porcelain coatings look phenomenal, but are considerably more fragile. I had a set on a car which was kept outdoors (OK, outdoors in So Cal) for almost seven years, and the porcelain looked almost as good as when the coating was new. Note that this was not a daily driver. I've not yet tried a set with the HPC Jet Hot coating, but I've heard good things.

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


I'm not certain of your particular application, but several catalogs I've seen list headers that fit such and such Olds, but won't work with column shift standard transmission.

This is due to the linkage running from the column shifter to the trans. I think this primarily applies to automatics. Note that this is the same equalizer link which connects the shifter to the steering column lock on post-69 floor shift AT cars and which must be removed to install headers in a post-69 AT car. It is unrelated to the clutch equalizer on MT cars. The AT linkage equalizer shaft runs between the shift lever on the transmission and the driver's side frame rail about under the front door post. The MT clutch equalizer runs from the back of the block to a bracket on the frame roughly under the brake master cylinder. I have a set of Kenne-Bell headers on my 70 W-30 and the clutch equalizer does not fit well at all. I had to shim the frame bracket and still run into problems at certain points in the clutch adjustment.

[ Thanks to Joe Padavano for this information ]


Collectors are also an issue. I recommend Hooker collectors for any brand of header. I found that these collectors retain a seal years longer than others even with ordinary collector gaskets. The last thing you want to do is weld the exhaust pipe/colletor/header all together to avoid leaks.

[ Thanks to John Schumacher for this informaton ]


Dynomax (formerly Blackjack) on a '70 442: The headers, the d*mn things hang down lower than the old set, I didn't notice this when I was under the car at home. I lightley scraped the right one while taking a tight left hand curve.

Hooker Super Comps: They were the only company that made headers for a stick car that would fit, and they still needed a small amount of modification.

Hedman's are ok, but there's more than a little surgery involved to get them to fit right.

Like a lot of you, I've had lots of fun finding a set of headers that fit "out of the box" with no additional modifications. If you have a 65-72 BB 442/Cutlass, buy a set of EAGLE Headers (A division of Mr. Gasket). A perfect fit with plenty of clearance for the starter and oil filter! In fact, I didn't even have to lift the engine.

Installation Tips

Installing headers usually requires the brake distribution valve to be moved. I managed to get all of the factory brake lines to reconnect afterwards except the rear brake line, this one ended up being too short, so I added a 6" section to it, I mounted my brake valve on top of the frame. I would highly recommend doing this before you install the engine!

When I dropped in my 425 big block, I had one HELL of a time getting the headers to fit right. It might be a possibility that you will have a hard time to. To avoid this, try dropping the engine in with the headers bolted up. It will make it harder to fasten the motor mounts, but it will still be easier than pushing them up from underneath. My big block is in my '70 olds. Also, You may have to bend in one of the header primaries on the drivers side of the engine as it may knock the steering column when the engine torques while going around a turn. Watch for this and take it careful when doing the first test drive.

I don't think that is possible. I think you have to put the engine in first & then you can bolt up the headers. Floor shift autos are the easiest to work around. Be prepared to move your starter wires. You'll have to route them down from the firewall.

Before installing the motor lay the headers in the engine compartment where they belong, then jimmy the motor in. If you try to put the motor in with the headers bolted to it, you will have a very hard time getting the motor on the mounts. Just make sure you have the starter and oil filter all bolted to the engine also. Putting them on afterwards isn't much fun once the hearders are on!

You'll have to get the engine back in to put the headers on. They can't be installed on the engine, and then put into the car. Likewise, you can't put the headers into the body and then install the engine. At least you won't have the starter, oil filter, & exhaust manifolds to take off as they are already off.

As for protecting the coated headers during installation, put the headers into trash bags, install the headers, then rip the bags off. Or, wrap them tightly in an old sheet and use masking tape to keep the sheet on. This will prevent them from being scratched when installing them, especially the driver side (when setting the starter on it). After they are on, you can cut the sheet off, making sure you get all of it off.

On a 1967 F85, and installing Heddman headers. Passenger side header fit without a problem. Will need to file the rear part of the passenger side upper control arm about 1/8" to account for any bushing flex so as not to put a hole in the #6 primary tube. Have to remove the oil filter adapter to install the headder. Drivers side headder will need to pull the starter motor and install the headder first, just loosly, then put the starter motor in. The braking system junction box might have to relocated.

[ Thanks to Mat Nadrofsky, Paul Rousseau, Bill Culp, Joe Padavano, [email protected] for this information ]


Fel-Pro makes a good Hi-performance header gasket that I have been using for years. They are expensive, but don't leak or blow out, and they come off in one piece and don't leave parts on the header or head. Ordinary header gaskets fail often and are no contest to even a back-fire. I've been running fel-pro metal combination gaskets for over three years on Cyclone headers with no leaks/burn or replacement yet.

NAPA Nitroseal also work well.

Use a header gasket instead of the silly little ex manifold gaskets. Or you could use a little TRV Ultra Copper from Permatex. Or you could use the copper seal gaskets from Mr Gasket. They are expensive, but seem to last. They are made of soft copper for crushability.

I have had great success using the exhaust joint sealer sold by NAPA. I have used it to coat both sides of header gaskets and exhaust manifold gaskets. It will fill any small areas and ensure a good seal. I like the thin metal/fiber gaskets (the ones that come with most Felpro, McCord, etc type sets) with the sealer for any exhaust manifold or header to cylinder head seal.

If you are using any RTV, try Ultra Copper sealant and follow the instructions. I was skeptical when a neighbor told me to use silicone on my header and flange gaskets. Again, it's not SUPPOSED to work because of the high temperatures, but it really works great. The type of silicone doesn't matter. I just use whatever color matches best!

[ Thanks to Jack Wendel, Kerry Kroger, Dave Wyatt for this informaton ]

Keeping Bolts Tight

I had a similar situation with a mid-1970's International Harvester 392 V8. The exhaust would come loose in a few days, and needed to be tightened. I think that that engine had a harmonic vibration that just shook the fasteners loose. I tried pal nuts, double pal nuts, double brass nuts all to no avail. One day I got tired of the problem and removed the exhaust manifolds, drilled the studs, and put on castellated nuts with cotter pins; end of problem.

I would suggest drilling your bolts, adding an attachment stud to the header flange, and use a cotter pin or safety wire tie to keep it tight, the cotter pin seemingly the best. It might be a bit of extra work at installation, but worth it in agrivation (sp).

Get Summit Racing's stainless steel header bolts. They have a reduced head size (7/16" wrench size) that makes it easier to get a wrench on them.

I've always just used red Loctite. You can also use the blue stuff. Never had a problem. If you read the spec sheet, the temperatures experienced are really past the operating range of Loctite, so it loses SOME of it's holding strength. That's why I can get away with using the red stuff (stud and bearing mount) yet still remove the bolts later.

Use a flat washer under each bolt. They were there originally for a reason, so it would be good to keep em'. Use stainless bolts with a stainless lockwasher. They don't come out unless you want them to.

The company I work for makes all metal self locking bolts. The first three threads are true but the next three are out of proper pitch. We make these up on the fly by smacking the bolt with a cold chisel and ball peen hammer. Works well.

[ Thanks to Cliff Feiler, Kerry Kroger, Patton for this information ]

Making them Fit

The headers will ding but you have to get them very hot. These are the instructions I got from Doug Thorley. I got out the old gas torches and heated slowly on the area till almost glowing, and then hammered a spot to clear the starter.

I had a '73 VC w/455 & AC. My problem wasn't the AC when it came to headers, but the starter and body braces at the lower rear of the engine area. The body braces had to be discarded & the starter removal was a chore. The starter had to be removed annually because of high heat destroying the solonoid. At ordinary rpm's, I saw no advantage either even though I had changed to a '70 442 camshaft, Edlebrock intake, Holley carb, & CD package for the recurved distributor.

[ Thanks to Bill Culp for this information ]

Routine Maintenence

To get the oil filter off, I found a cheapie ($3) oil filter wrench at the local discount auto parts store that just has a thin (1/2 inch) curved arm that has teeth cut into it. Then there is a smaller pivoting arm that bites into the filter. This is the only wrench I have found that will fit.


For a smaller starter, I contacted the Hamburger Co.(a division of Mr. Gasket). They have a starter they say will work, because they claim the mounting block is adjustable. I did try another aftermarket hi-perf hi-torque mini starter, but the solenoid is clocked away from the engine block, causing a bigger interference problem. I called others and they have the same design, except the Hamburger brand.

1979 Cutlass

This should apply to 1978 to 1988 Cutlass'. I used Hedman Headers, model number 58070. They are a nice header, but do require some work to install them.

The easiest side to install is the passenger. I have found that if the oil filter housing is removed, the header will slide right up into place as long as the car is up on jack stands. If you are installing the engine for the first time and have pre-oiled it, you will probably want to set the header in first and then the engine. This will save you the grief of removing the housing and having oil drip everywhere. Besides, it is more important to keep the oil passages air free when firing up the engine for the first time.

The driver side is a little more tricky. If the engine is allready in the car, the header and starter will have to be installed at the same time. I usually hold the header in one hand and set the starter on the header and carefully lift the two of them in place. I then start the bolts for the starter and then bolt the header in place. The upper A-arm can sometimes interfere if there is alot of shims in it, but this can be solved be removing some of the material with a grinder. Tubular upper A-arms would solve this but they are a bit pricey. If you only have a few shims, this shouldn't be a problem at all. You can also set the header in the frame first if you want but it is sometimes hard to keep the two headers out of the way while setting the engine in.

One thing to keep in mind is that these headers do not dump straight back. Both are pitched at different angles. I used Torque Tech's 3" pipes and they sell a special setup for this type of problem, but you must have access to a welder. It took me a while to put the exhaust on but it was worth the time and effort. Headers themselves are a major project but I definetly think they are worth it.

One more thing to think about is the cross member. For some unknown reason, G-bodies used an offset cross member that only has a single hump. A dual hump one from a late 60's or early 70's GM (Cutlass, etc.) will work great if you remove 1" from both sides. It will have to set on the bottom of the frame rails instead of the top but it will work just right for the where the headers dump. I used one from an '73 442 and it works great. I have 3" all the way back with no clearance problems at all. If you want to retain the original cross memeber, 2 ½" pipes will fit under it on the driver side, but they will be close.

1985 Cutlass with a 455

I am using the 3203s. The long and short of it is that they do seal, but your block placement has to be exact. For the #7 & #8 tubes to not hit the frame rails, the frame needed to be re-drilled for the motor mount pads.

Best way to install them is:
Dropping the transmission down is the most useful move you can make. Have the block out or lifted 2-3". Remove trans cross member and drop the tranny down 3 to 4 inches. Don't seperate the trans and the engine; it doesn't gain you anything. I spent 5 hours stripping header bolts before I realized "Hey there's just not enough room to wiggle these things, I wonder what would happen if I droppped the motor and transmission down?"

Insert the headers from the underside; mate them up from front to rear for the #7 and #8 tubes: dry fit them and cut the fiberglass fenderwell to get them in. The #7 and 8 are seperate so don't drive them into the collector too far or they won't seal. A rubber mallet worked fine for me. Remove the catylitic convertor heat shield if they touch at all at the collector.

[ Thanks to Tom Millard, Brian Kennedy for this information ]

Leaks & Noises

An exhaust leak may be caused by rusted A.I.R. tubes. Replacing them looks difficult but it's not too bad! Exhaust leaking from holes in these tubes might also sound like engine knock or lifter noise upon acceleration. There are usually rusted on the undersides.

While on the subject of A.I.R. manifolds, I'd like to share a helpful tip. Most of the time on the 307 cars I've found that the wiring and hoses are too close to the one way valves that screw into the A.I.R. manifolds. Mine were too close and the MAP sensor vacuum line burnt through. Luckily no wires got burned!

ALL LATE MODEL V8 OWNERS: Please check yours! 5 minutes and a few wire ties is all it takes!

[ Thanks to John Pajak for this information ]


For pipes, most shops that custom bend use aluminized pipe. Most pre-bent pipe is mild steel, which rots out after a couple of years.

[ Thanks to Andy Green for this information ]

Single to Dual Exhaust

You can go get the entire dual exhaust piping/mufflers/clamps/hangars for a stock dual exhaust with straight tailpipes (for the tips) from NAPA or some other parts store. It should bolt right up (See #3 also) If you want 2.5" pipe or larger, Flowmaster and others make header sets, but the stock tips won't fit and it's designed for header applications.

Since dual exhaust was a factory option, you simply need to go to your auto parts store of choice and get all the necessary parts. I seem to recall that the factory single exhaust piping is common with one side of the dual system (it's been so long since I owned a single exhaust A-body that I can't remember which side the single system is mounted on!).

I found the restoration places to be all about the same price as each other, but cheaper than NAPA and such. Yes, the pipes are still produced by Walker et al.

Your existing dual manifolds should work with a Conversion Kit. But if you snap off any bolts it will double your fun. Plus, you will need to block off the cross-over pipe inlet on the passenger side manifold. You could just buy some dual exhaust manifolds, but these seem a little pricey.

One problem is the driver's side exhaust pipe to manifold installation. Things could get tight in here, plus the bolt pattern isn't real condusive to straight-on bolt tightening/loosening. Passenger side is a breeze in comparison.

If you are planning to use the cutout bumper, you will need to tailpipes for a 442 as opposed to a Cutlass. The normal Cutlass pipes had downturned tips which will not line up with the bumper. The cutout bumper also used unique tailpipe hangers with keep the pipes lined up with the cutouts. While the correct hangers are not available, I believe the repro parts vendors (Fusick, Year One, etc.) sell replacement hangers which work but don't look original.

Also, you may find that the aftermarket rear hangers aren't very well adapted to Oldsmobile factory dual exhaust configurations (i.e. mounting holes), but if you don't care about originality, then they should work just fine.

Small block specifics
The factory never made any true dual exhaust small block exhaust manifolds. They used a block off plate on the driver side crossover outlet instead. There is a crossover pipe which runs from one exhaust manifold to the other under the oil pan, resulting in one of the manifolds having two outlets. The factory dual system used this same manifold with a cap on the unused outlet. This cap is apparently no longer available, however any exhaust shop can fabricate one by using the bolt flange from the crossover pipe and welding a piece of sheet steel over the hole. The other manifold is also common with either the single or dual systems.

There were no dual-exhaust-specific exhaust manifolds for the small-block (no, not even for the W-31), and the RH Big-block dual-exhaust manifolds will not fit. Use your existing manifolds with a cap over the extra outlet (a pipe can be crimped neatly for that purpose, if you can't find a cap).

Just order the pipes for a normal small-block dual-exhaust system, and get a cap for the manifold; the replacement exhaust will never know that it is performing a "conversion."

Other than those above concerns, this is pretty straight forward swap.

[ Thanks to Mike Rothe, Bob Barry, Joe Padavano, Thomas Martin for this information ]

Transmission Crossmembers

Even though your car is equipped with single exhaust, it may have a dual hump crossmember. This only applies to pre 1975 cars. 1975 and after, a catalytic converter was mandatory, and all cars had a single exhaust. Even ones with dual outlets. In order to save money, only one crossmember, designed for a single exhaust, was used. OTOH, an earlier crossmember can be adapted to be used in a later chassis.

[ Thanks to Bob Barry for this information ]

Vista Cruiser Exhaust

You would need different tail pipes to clear the storage well and spare tire well. Probably need to have them custom made at a muffler shop with a pipe bender to clear everything and still come out the back. Vistas also have a longer wheel base than the Cutlass that has to also be considered.

For dual exhaust on a Vista Cruiser, try a similar year El Camino listing for the tailpipes! They exit behind each rear wheel.

[ Thanks to Wayne Drusch, John Pajak for this information ]

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