Dint rebuild an Olds 350 for a while, and my old catalogs dont show the reality ......

the car is a 1970 Rallye 350 , 4speed muncie ,with 3:42 posi rear end .....
the car is pristine but the engine is really tired ( 50 years lots of mileage and been rebuild with .030 over pistons about 22 years ago .....

I want to achieve a final compression ratio of around 9.5 to 1 ....... customer does not want to run on 94 gas

I used to fiind quite some pistons choices for 455 s ,,,,but for a 350 pretty rare !

W-31 pistons are flat top but achieve 10,5 CR with the code 6 (64cc) heads , too high
the regular 70 pistons yield ( as per GM ) 10.25 CR

Not many choices either in cast or forged .....

Maybe ill go for deep dish ( 8,5 CR ) and shave the block & heads to attain 9,5 CR
I know ill have to go for adjustable valves ( studs, plates & rockers )

unless someone knows about new pistons that gives better CR for our intentions
any inputs on this ?

thanks
Dan

 

hey Dan

contact cutlassefi on this site he has some new olds 350 piston offerings w a modern ring pack

also i think the 64cc number is optimistic.

 

The Mahle 10cc dish forged pistons with 1mm ring packs Cutlassefi brought to the market will give you exactly what you want. They are available up to a 4.155" bore I believe, so whatever oversize needed will be available.

 

Agreed, 64cc is the NHRA minimum spec and not the actual volume. In several polls, most folks reported 66-70cc, with the majority being on the upper end.

As for pistons, there are several options - check with cutlassefi as said above.

 

thanks ,

the heads CCs are at 65 CC measured ,,,,,,
thanks for the reference ill contact them
Dan

 

looks like those Mahle NO 197815300 are the ones to go for...... 9,5 CR , forged .040 over ( engine at .030 over already )
thanks for the reference !

combined with the Comp cam : XE 262 H or XE268H ,,,,,,should give great results !

 

Yep, Mahle piston sizes are 4.065, 4.100, and 4.155. They’re going to add a 4.125 soon as well.
I can get those at a real competitive price too. Let me know. Hope this helps.