Which piston is the best to use for top end? Flattop, domed, or cupped? For road racing.

 

and the combustion chamber config.


But, current thinking is go with a reverse dome (kind of a dish) and a very small chamber. This helps move the actual combustion process to the center of the piston as opposed to the center of the combustion chamber.

 

I agree with jcb. The current trend is dished pistons with small combustion chambers. They also promote more "swirl and tumble" which allows you to develop the same power with less spark advance.

Also tall narrow ports are now becoming quite popular - the narrow design gives good velocity at low rpms yet allow for large flow at high rpms.

 

Oops, hit the wrong button....

What will 194 heads do with cupped pistons? Will it make a big diffrence?

 

AFAIK there's no such thing as "194" heads. That's not a casting number. It might be the intake valve diameter, but there's a huge variety of heads that came with that size valve, all the way from 62 cc chambers to 76 cc chambers, and everything from the hottest late 60s-early 70s motors to late 70s somg garbage. Some are terrific, some are crap for one reason or another.

Post the casting numbers.

 

Casting number is 3932441. They are off a 70 Impala.

 

Rocman, Here is the head info for 3932441, Year 1967-1979, Engine size used on 327/350, CFM intake152 exhaust 93, Factory HP 250/255, Valves 1.94 in./1.50 ex., Chamber 76 cc. Hope this helps.

 

I imagine that is 152 number is the intake port volume in CCs as opposed to flow. But, the main point is the chamber volume. 76cc. Way too big.. think 58cc or smaller.

 

Thanks for the info. I have a Performer intake and a 650 Edelbrock on the motor now. So these heads should be o.k. with that?

Thanks again!

 

Those are not very good heads. They're better than some of the later 76cc castings such as 882, because they aren't thin in critical places and crone to cracking; but they're not a performance head by any standard. They went on the 2-barrel and low-end 4-barrel motors. The ones that went on the better Impala 350s were the 186 casting, which is an excellent casting as the more plentiful stock ones go.

Get something else if you want something that runs good.

 

compression with a 350 using a flat top piston and a 76cc chamber.

but, as rb said.. try to spring for a higher quality head.
even the 186 castings are nothing to write home about. They just have a little more compression really. No additional flow as such..

think aftermarket.