im tryin to figure out my compresion ratio and i need to know the cc of the valve realeafs of my pistions. its a flat top pistion for a .030 over 400. it has your typical 4 half moon releafs.ive been told it like 10 cc, but i wanted others opinions. thanx

 

not much more.

 

Yeah, 6 cc is about as big as they get, about 4cc is the usual

 

Is 4-6cc about right for a flat top slug that has 2 valve reliefs, or 4?

AJ

 

the 2 valve relief pistons are normally .26 deep. that works out to about 6. If there are only 2 that are .16 deep.. your about 3.5 to 4.

 

HUH?!?!?!

So are you saying that 4 valve reliefs (which is what the Speed Pros I have are) would then be 12cc's if they're cut .26" deep? Since you said that 2 of them would have 6cc's of volume, then 4 would be 12cc's?

That's no different than if I would have just bought 12cc dished pistons!!!!!!

I hope that you made a typo, 'cause that sure don't sound right.

AJ

 

.
Because pistons like that are meant to go in ether way.

Speed pros are normally just a forged version of the factory piston. Same dimensions on everything.

Here is a pretty good example..
the trw 2256 is a forged 4valve relief piston with a volume of 6.1 cc. The trw 2417 has a single trough for the reliefs and it is 3.4 cc..but I think neither of these really have deep reliefs. Hiperf pistons from companies like Weisco and SRP are the ones meant for really big cams and hence have deep reliefs.

Based on my experience.

Now.. if you want to talk dish pistons.. or the 00 term.. reverse dome... they really start looking good when you have about a 48cc chamber. And that will screw up the airflow of a 23degree head. 18dgree are designed to have the flat chambers and reverse domes. Flow remains good.