Ok I bought a stroker kit 340-416, Callies forged crank 4.0 stroke, eagle h beams diamond flat tops, here's where i'm concerned: these flat tops are rated at 11.8 compression for a 65cc head. The heads I have now are stock small-valve heads. I want to keep this pump-friendly, what do I need? Thanks, any help appreciated..

I'd send those flat tops back and get some dished pistons if a pump gas engine is what you want. Then get some closed chamber heads like Edelbrocks and build a quench combustion chamber engine.

well, you need a big enough cam with a late enough intake closing point to keep "dynamic compression" below 8:1. your stock 72ish cc heads will drop compression down into the 10's...or closed chambered aluminum heads (i.e. eddies, indy) w/tight quench can run on pump gas in the 11.5:1 comp ratio range with the right cam selection

another option, water inject it to control detonation. you could run a lower octane and/or a smaller cam then and have your "dynamic compression" higher, and you might actually see an improvement in fuel economy.

My pump gas stroker has the eddy heads. -16 dish pistons, static is 10.6 dynamic is 8.2 and my quench is .035 and its a very good combo. Even dish pistons need good quench were it counts the most.

Its obvious patrick is very smart, I could of went higher on my static with the al heads but this combo seems to work so well.

Here are two links that might help you understand things a bit better.

Even though the second one is from a poncho site its pretty close, just fill it in with the right numbers.

Just remember strokers will eat duration like crazy, pic the right cam.


http://www.empirenet.com/pkelley2/DynamicCR.html

http://www.projectpontiac.com/ppsite/content/view/16/30/

You might as well take the plunge and get some Edelbrock heads. Zero deck the block and select a cam that will get you in the 8.2 to 8.5 dynamic effective compression range. It's all in the cam selection. If you want an engine that makes more low end power go with dished pistons and select the cam accordingly. That is what I used and am very happy with my Magnum headed engine. No need for a high stall converter either.

Thanks for the help guys. I sent the flat tops back this morning ups and ordered the dish pistons w/9.5 compression @65cc. Only thing is I had them balance this kit before they sent it to me, I guess I will have to have a machine shop locally redo the balance with the dish pistons.The balance card says piston 527.8 pins 131.6 on pistons I sent back. Thanks