blackz151

I am getting read to order my bottom end and I just need help deciding on pistons. It will have a comp star crank and rod combo. Stock 243 heads stage 1 from frankenstein. The car will be a daily and may see the track here and there with a little spray maybe.

Would the flat tops be the best? I was looking a diamond -2cc flat tops or -10cc dish.

redtan

iTrader: (5)

Can't answer that question without knowing more details about the heads, gaskets, cam, type of fuel you plan on using

blackz151

Stock chamber head 64cc I believe. I was looking at the MLS gasket. I have no spec'd a cam yet for it. It will run pump 93

Mavn

iTrader: (3)

Flat tops... Dish for Boosted Applications

blackz151

Thanks!

KCS

iTrader: (20)

It is not that simple!

In a 402 with a 64cc chamber, a 2cc flat top could end up with 11.9:1. That's REALLY pushing it with pump gasoline. If I ran flat tops in my 440 with 59cc chambers, I would need race fuel or ethanol with 13.5:1 compression.

OP, use a online calculator to figure out what compression you will end up with for you combination. I like to use This one.

blackz151

Thanks for the info Im looking at it now. So what is a safe number on pump? closer to 11?

Please excuse my ignorance first motor build trying to get it all worked out right

R6cowboy

iTrader: (3)

Approx. 11:1 compression is plenty safe for 91 or 93 octane. A 4" stroke 402ci LS2 with 64cc combustion chambers will need a 8cc to 10cc dished piston to keep compression close to 11.0-11.2:1 using a 0.040 thick head gasket.

KCS

iTrader: (20)

Yeah, 11:1 to 11.5:1 is pretty safe. If you plan on doing some long runs, like at a Mile event or similar top speed type racing, I would suggest closer to 11:1.

There are guys that will tell you you can go higher, and you can, but it's usually not worth the trouble. When you get close to 12:1, the potential gains from the increased compression are often negated by how much ignition timing you have to take out of it to keep it from detonating.

blackz151

Thank you for the help. It has made this much easier as I do more research.

What would the bore size for the gasket be?
4.040?
4.02?
4.03?

blackz151

I understand. I don't think it would as much as Id love to see the mile.

Quick Ranger

iTrader: (2)

Depends on the chamber of the heads. If it is a stock chamber 243, most likely the 4.020 will work.

blackz151

Thank you.

R6cowboy

iTrader: (3)

I agree. Stock chamber 243 heads and typical 4.005" 403ci bore (commonly called 402ci), 4.020" gasket is ideal.

blackz151

Thank You thanks for all the help so I can understand all this.