Olds71suprema

HI again from Germany,

Im tryin to rebuild my 350 olds engine (its a 1971 Olds cutlass Supreme)

Now i want to raise my low compression of 8,5:1 a bit...

I found Flat top pistons on summit from speed pro ...
the discription says they fit on olds from 68 - 70 with oai...

My question is: do they fit my 71 350 with the #7 heads (i think they have 64cc, is this right????)
because of valve to piston clearence???

Has everyone done this before with the same combo???
by the way here is the list of parts i have already:

Comp Cams valvetrain kit with roller tip rockers
Edelbrock performer rpm intake
Melling Hi vol. oil pump
Moroso 7 qrt. oil pan
Alum. Hi vol. water pump
Complete set of stock valves stainl. steel 1.875 in 1.562 ex.
New performance balancer
Carburetor now is an 600 cfm holley (maybe i get some 750 holley cheap)
Hei ignition
Headers with some custom dual exhaust is installed already
New th 350 is installed
Gears are now 2.56 but will be changed as well

For the pistons i dont know yet, either standart bore or .30 over ...
But at first i must know, if the pistons work.....

Thanks to everyone who could help me ....!!!!!!!!!!!!!!!!!!!!!!!!!
Greetings from Germany
Torsten

J-(Chicago)

They work, and work pretty well.

Warhead

Valve to piston clearance is NOT an issue with the Oldsmobile engines like they are Chevrolet's, because the valve angle on the Small block chevy is at 23 degrees, leaning the head of the valve at an angle that can interfere with the piston. That's why they have pockets in the pistons.

Oldsmobiles have a 6 degree valve angle that does not come near as close as the chevy does. While the angle does not promote airflow as well as the chevy, clearance is hardly ever an issue, unless you run massive cam (250@.050 or more, with .580+ lift). IT NEVER hurts to double check it, however.

Those pistons do not come with valve notches, but if there is a clearance issue, Isky makes a great tool for the DIY guy.

Is it too late for you to get a set of 2 inch intake valves?

600 holley? How about a nice 735 quadrajet?

BTW, #5,#6,#7,& #7a's will never, ever, ever,ever,ever,ever come from the factory at 64cc's, unless someone has milled them at least .040 inch.
They come in at 68cc's at the barest minumum.....FACT.

VERY good piston, make sure your machinist gives it at LEAST .004 piston to wall clearance, and have him pin fit the pistons. If you don't, it may cost ya.

Jim in Phx.

#1CutlassSupreme

I have a 72' cutlass Supreme with the same heads and I did just about the same thing with the Speedpro Pistons. I went .30 over on mine. I'm not sure if you're going to find Olds flat tops in a bore smaller than that. My machinist tried to keep the bore down to .20 over, but had to go up from there because we just couldn't find smaller F/T pistons. No big deal though. If they machine the head down a little you'll get close to your 64cc, you might also try to shoot for a thinner head gasket. The Speed Pros advertise 10.5:1 but expect around 10:1CR.

Sounds like a good build, are you upping the cam too? If you're putting those spendy pistons in you may as well throw a few more bucks at it and do the cam too. I did a Crane Powermax cam with .496int/.512exh and hydraulic lifters. That should match pretty well with your pistons. That cam isn't too aggressive and might help your engine breath a little better with those little exhaust valves in that #7 head.

It's a pretty mild cam and it's not so radical that you'll have to nurse the pedal it to keep the car idling, but it will give it a little more poop than stock. I wanted to keep mine close the the Olds W31 specs for the 350 and that cam is pretty darn close. (W31 was .490/.490.). The W31 was a pretty potent Olds 350.

Anyway, good luck and keep us posted on what you decide to do.

-Roman

Quick FYI Summit has the flat tops listed on their website, but when I bought mine they informed me that the site was incorrect and that they were out of stock. You may want to try Jegs if they are out.

The_Jeremiah

Damn, makes me wish i found those before i rebult mine, im stuck down in the 9 area still. I didnt even know that the newer pistons had such a bad dish. I have heard that it affects your compression ratio badly, and that it doesnt at all, so i dont know for sure, but i know if i would have found the flat tops before, i would have bought em. good luck

tonycpe

comp cams roller tip rockers may not work correctly..they ruined my guides.

joe_padavano

The 68-70 W-31 motors used the flattop pistons with the 64 cc chamber heads with no problems. You won't have any problems either.