Olds 350, Differences between 1970 and 1972

[KCEE442]

so im going to pick up a motor and ive got it down to two motors,
the one is a 1970 complete long block and and the other is a 1972 complete long block

from what i gather, i come to thnink that the 1970 motor would be a better bet over the 72
what are major differences? in 70 the compression was higher and the heads were better flowing right?

Ive already got hedman headers,edelbrock intake, 600 cfm carb, proform dist and a msd 6al box
and was planning on getting the heads done:3 angle valve job,port/polish, and mill for better compression
also a nice cam, roller rockers/lifters

any suggestions?
thanks in advance!

 

[Minion1186]

yes,1970 block is the way to go,reason behind this is simple-more power,stock compression is bigger than the 72's (unless it has heads shaved and moded)and has if any little to no smog equipment on it like egr.I would ask the guy if the 72 and 70 are stock,like for example,if the 72 is cranking out 100 hp more than the 70,than get that.The 72 350's came with 7A heads,were as 70's had #6 cast heads.He may have changed the heads over,any smallblock heads from #5 to #8 and possibly 3A's.

 

[84 W40]

I agree with the last post. Check the heads on both engines and the 70 engine is what you want if has #6 heads. If you want to raise your compression buy flat top pistons.

 

[FE3X CLONE]

I'd buy the '70 due to the compression increase (assuming its all stock) however the flow difference between #6 and #7a heads is very minimal that you'd never tell the difference. So I would let the heads deter you from one vs the other.

 

[KCEE442]

Ok yeah thats waht i thaught, i knew the 70 had more power and compression stock.
both motors are 2 individual sellers, the 72 is all stock with 41k and 7a heads (supposivly)
Im still waiting on casting #s on the 70 block.

If the differernce is very minimal between the 6 and 7a heads, and i already plan on milling the head for
better compression it sways my decision to the 72, unless the internals are differnt? pistons?

Thanks again

 

[Minion1186]

I have a 1973 olds 350 with the 1972 7a heads that are shaved to 59cc heads,engine is decked to 0 and yields an 11:77.1 compression and 402 horsepower.Just a thought of what you could do,even with a smog built engine originally making an 8.0 compression and 180 horsepower.

 

[KCEE442]

I have a 1973 olds 350 with the 1972 7a heads that are shaved to 59cc heads,engine is decked to 0 and yields an 11:77.1 compression and 402 horsepower.Just a thought of what you could do,even with a smog built engine originally making an 8.0 compression and 180 horsepower.

Wow! thats sicck!
if you dont mind what elese do you ahve done to the motor?

 

[Minion1186]

it has been bored .30 over,has speedpro forged aluminum flat top pistons,edelbrock timing chain set,comp cams high energy pushrods and 1.6 ratio rocker arms that are full roller,mondello soild roller lifters,lunati 244/304 camshaft,clevite bearings,edelbrock performer rpm intake manifold,holley race 4150 750cfm double pumper carb,hei ignition with DUI coil,accel 8mm wires,dynomax headers.It makes 402 horsepower @ 5000 rpm and 499 FT LB torque @ 2500 rpm.The 7A heads have been completely ported and has 1.995 intake valves and 1.624 exhaust valves.It was in an 86 cutlass supreme drag car with a th350 and 3.55 gears with posi and ran 12.50s,thats damn near perfect for me

 

[jae]

Also, you'd want to know about the pistons, if they are stock or not. That's where the different ratios come from with these, the amount of the dish in the piston. Both engines have 64cc heads as spec'd from the factory, same intake valve size but the 7A has a W31-sized exhaust valve of 1.624 (W-31 intake valve was 1.995). '72 has hardened seats too. As stated a couple times you'd want to go with a flat-top piston, that'll get you some compression. Wherever you take the heads make sure they are familiar with Olds heads / engines and have good equipment. With all the nickel in them they will blow through cheap cutters, bits and disks in a hurry.

In terms of the intake, did you get the Performer or the RPM?

In either case it is a very nice motor and keep us posted with what you decide.

 

[joe_padavano]

There are virtually no differences between the 1970 and 1972 Olds 350s. The blocks are the same casting. The cranks are the same cast nodular part. The rods are the same. The compression was dropped by increasing the size of the dish in the pistons, but depending on which 1970 motor you're talking about, this could only mean a drop from 9.0:1 to 8.5:1. The most radical cam profiles were dropped, but the most common motors used the same cam profiles. The 1972 heads have the same combustion chamber size as the 1970 heads, but have induction hardened valve seats (a plus). The 1970 and 1972 heads have the same flow properties. The W-31 motors simply used the larger big block valves in the same #6 casting. Any small block head can be machined for these valves. As for "smog equipment", the only differences are in how the transmission controlled spark system is connected - and it is easily bypassed by moving one hose. There is nothing else. EGR was not used until the 1973 model year.