found places to figer out compresion ,but thay ask for piston dom and how far they set in the hole,and also gasket thickness,,, got this old 402 bored out .040 and 100.9 heads ,,can i put this thang together to run on pump gas, ( to 10.5 compression ,any cheap pistons ,whitch ones?like to put it togather since i got it ,been seating ,clean and bored for 15 years now.Then i could say ,,hay look i got a big block ha!

I am know expert on parts selection, but I believe you should let your cam dictate what pistons you should buy.

The only thing the cam really dictates is how much compression you should be running, if it's a big cam then you'll want more compression just to make it behave better. 10.5 should be able to handle most cams pretty well.

If you know your combustion chamber volume and piston bore, you should be able to spec pistons with that info. The dome/dish height is only needed if you already have a set of pistons and want to know how much compression you'll get out of them. If you buy from Summit or Jegs or other big places, they should list the compression each piston offers with differing combustion chamber volumes.

Edit: just checked summit, some pistons list compression and some don't, but they offer dome height and piston head volume.

Tell your piston supplier that you want pistons that when using stock spec's like .025" down-in-the-hole, 101 cc closed chamber heads and .020" thick steel shim headgaskets that will give you right at 9.75 to 1 so you WON'T have any problem running good pump gas!

I told ROSS Racing Pistons I wanted 9.5 to 1 in my 496" engine using stock spec's, a 119 cc head and .039" thick composite headgaskets and they sent me just what I wanted! Then I changed my mind and used .020" thick shims vs .039" thick composite headgaskets to put me right at 9.8 to 1 CR!!

And at 9.75 to 1, you can run anywhere from a 270 to a 284 or so cam fine...........

Imho.....

pdq67

thanks all, just never had to dill with big block ,and sence thay all seam to have some kind of dome ,don't know how to figer it all out ,thanks

bttt

You need to cc your BB heads b/c they can vary ALL over the place!!

Closed and semi-closed chambered large oval port heads go from 96.4 or so to 101 or more cc's!

Open chambered heads range from 112/113 all the way up to at least 120 and some guys say as big as 124 cc's!!

pdq67

wont to put this in a 56 chevy truck may be do some pulling another trailer and a car may be with a 700 r 4 trany and a 3 somethingother rear ,but would like it to run pump gas .should i sell it and just buy a stock 454 , be cheeper i thank ,,all i got is the block ,heads and crank,may be the cam around here some where ,,block was bord out.o40 and cam bearing put in 10 years a go ,, what you thank ??????