General Information
Note: The information contained in all
of the "Engine Detail" sections should be read before proceeding with
modifications, etc., because some information that applies to all engines, or
all small blocks or all big blocks, might not be duplicated in every section.
The 350 was built from 1968 through 1980, produced from 160hp to 320hp,
and was installed in just about every car Olds built in that period at
one time or another, including the Cutlass/442, Delta 88's, 98's and
Toronados, and the Omega. You can get a quick estimate of the year of
the engine by looking at the 1" high casting number on the lower-left
corner of the block and/or head.
Watch out for windowed main webs on 1977 and later blocks. This limits sustained or
occasional high RPM usage. All diesel 350 blocks are solid main webbed.
Performance
1974 350: 180 [email protected] 3800 RPM; 275 Ft-lb Torque @ 2800 RPM
[ Thanks to Matt Cremean, Bob Barry for this information ]
Buildup
First, congratulations on not getting sucked into the "gotta have a
455" mentality!
Example(s)
A set of mildly-ported 2.00"/1.62" early small-chamber heads will let you
spin into the higher RPM range. The only non-factory part
you may be interested in is an
aftermarket cam and intake, and a high-volume oil pump. If Edelbrock can
get 370hp from such a combination, where only the intake and exhaust are
non-stock, then you certainly can, and it will bolt to your existing
transmission, and the holes for the frame mounts are already drilled, and
it will look completely stock, and it will go strong for 200,000 miles.
Any '68-'72 350, with mild modifications makes a reliable and strong street
engine.
[ Thanks to Bob Barry for this information. ]
Short Block:
- Forged 10.25:1 pistons.
- 403 rods w/ARP rod bolts. Slightly stronger than 350 rods.
- Forged 330 crank, if you have one lying around; otherwise, the
nodular iron crank from a 350 would do just as well.
- Main studs. Optional main cap steel straps.
- Windage tray and 6-quart oil pan from Toronado.
- Make sure the oil that winds up in the heads can drain back freely.
Don't try to go for max cubes with the overbore. Simple reason,
if something happens and you have to overbore again you'll have
to chuck the block.
Heads:
- #5 or #7 heads are an excellent starting point; add hardened valve
seats if you're going to be doing a lot of towing.
- The variance between the 5 to 7a heads is small.
- Stainless steel 2.00" intake valves, 1.62" exhaust valves.
- 3 angle valve job.
- Going for larger valves depends on the cam. A waste without a large
enough cam to see the benefit. The exh valves should be fine but the
intakes could be raised up to 2.072.
- Mild porting. Grind down the smog bumps in the exhaust ports, teardrop
the valve guides, and a little cleaning up in the bowls does wonders.
- Roller rocker kit.
Valvetrain:
- JM18-20 cam from Mondello.
- Stock-style valvetrain; use longer pushrods and shims to get proper
preload, if necessary.
- Get a true roller timing chain, and by all means, DEGREE IN THAT CAM!
Induction:
- Performer 350 intake, or stock iron pre-EGR intake, if
you're running out of money.
- Olds A4 intake. Aluminum and plentiful.
If you really want to dust 5.0's, go with the Performer RPM. The
Performer is supposedly no better than a stock Olds intake.
[ Thanks to Mike Bloomer, Bob Barry for this information ]
Rebuilding
Example(s)
I just rebuilt my '72 350 about 3 months ago. I used new cast pistons,
edelbrock performer intake, and a melling camshaft. Melling, you say? Well i
just so happened to look in one of their catalogs one day and noticed the
specs on one of their cams. The exact same as the performer, only mucho
cheaper. I have a toro oil pan, melling oil pump, nodular
crank, stock rods, oil galley restrictors, cloyes true roller timing chain,
moly rings, and #7 heads with new exhaust valves, springs, ect., and I ground
down the AIR bumps in the heads.
I'm running a quadrajet out of a '80 or so eighty-
eight. Distributor came out of a '78 toro. I love the way the engine runs!
I ran the edelbrock specs through a program of mine, and it says im making
around 290hp. I'll definitely believe it as i have outrun several 5.0s even
with an auto and 2.29 gears. I had very few problems with the install into my
'78 cutlass.
[ Thanks to for this information. ]
Tuning / Power Boost
In 1970, the 350's had 9.0 CR with a 64cc head. In 1971 the CR
dropped to 8.2 with the same cc. This was accomplished with a "dish"
in the piston. This carried over until 1973 when the CR dropped again to
8.0 BUT with a 79cc head. This means that the dish was gone but the
large chambers in the head caused a further drop in CR. Going from
the stock 79cc heads to the earlier 64cc will bring the CR up to around
9.2 but with the thicker head gaskets than stock you can figure on about
9.0:1 "true" CR. This will definately wake up that motor and with a cam,
4bbl, and dual exhaust you should get 250 HP net easily as long as the
bottom end is in good shape. I would definately take a look at the
bearings. Since they were used to only 8.0 CR, jumping up a full
point might hammer them pretty quick if they are already worn. Some
plastigauge works wonders.
[ Thanks to Mike Bloomer for this information. ]