I know there is a formula to calculate it but was wondering if anyone could get me a ballpark number Would like to be somewhere in the 10-1 compression My combo starts with a 75 blue block. Stock rods and crank. fresh .30 over cast low compression pistons. I have 2 options on heads Set 1. 1972 iron heads stage 1 stainless valves some port work and have been milled. 64cc combustion chambers. Set 2 is a set of 72 iron heads stock with a fresh valve job. 71 cc. Both sets have stage 1 springs. And stock rockers Planning on using a performer intake and luanati voodoo 268/276 cam. And felpro blue head gasket. Combo is going in a 71 skylark with a 3.73 gear and a mild built 350 turbo. Trying to put this together with parts I already have. Just looking for a good street maybe light strip use. Any insight about this combo would be appreciated
Without knowing exactly what pistons you are using, and their measurements, compression distance,and piston dish cc's, you can't get any kind of meaningful estimate. That's the bottom line. You have the heads off, measure. Piston dish cc, and how far the pistons are in the hole. You need to know the true static compression to pick the best cam. The stock 75-76 Pistons can be as much as .085" in the hole at TDC, and can have as much as 35 cc in the dish. So with your 64cc heads, this is the best you could hope for,
To get an accurate compression ratio, you need to know the following: Stroke Bore Piston dish+/dome- Combustion chamber CC Head gasket thickness and diameter Piston depth in+/out- of the bore
Pistons can be purchased with compression distance taller than the stock 1970 pistons, which are 40 thousandths taller than what you have now. Less cc's at the dish are another factor. Thinner head gaskets can be used too. Lots of potential in a piston swap here. Add ARP bolts while your at it
Being the stock 75/76 455’s we’re rated at 7.6 to 1 STOCK, and we all know they fudged that, probably more like 7 to 1. You have a tall ladder to climb just to get to 8 to 1. I’d have a machinist calculate what size piston you’ll need to get close to if not zero deck.
Thanks for the reply’s. Sounds like I may need a different combo to get closer to what I was looking for. I really thought that the small cc heads wound make more of a difference
Swap some 70 pistons in,...deck block .020,...027 Cometics,..with the 64cc stage heads and that cam,...then you'll ha e a little something Nevermind you're 30 over,...so now you're talking new pistons,.....which means rabbit hole,.....
It’s good you asked instead of assuming the heads would help more than they will. Get custom pistons made by Auto TEC.
