Im building a 351W and the pistons I have are listed as 9:1 when using a 64cc head. Can anyone tell me what my compression would be if I used the same pistons with a 58cc head? I want to be able to run pump gas but there are alot more aftermarket aluminum heads with the smaller chambers. I realize that I should have picked the heads first and then matched the pistons for the desired CR but that not the way it happened. I put the cart before the horse and now Im trying to see if I can keep the pistons, or if Im going to be shopping for new ones. Any help, advice, or info is appreciated!

 

check this out

Engine Compression Ratio (CR) Calculator

this will let you plug in all the values like chamber size, bore diameter, head gasket thickness and others to find almost the exact compression ratio. Pretty neat if you ask me

 

Thanks. I will check it out. Im not sure about the head gasket thickness or some of the other values they want to know. I guess I'll have to figure that stuff out. I guess Im kind of looking for a ballpark figure. Something like; for every cc point drop you get approx. .2 increase in compression. 64cc head = 9:1 so 62cc head = 9.4:1 I know thats not an accurate # but thats kind of the info Im looking for. I dont know if you can even figure it that way but I figured I would ask rather than trying to figure out swept volume, gasket thickness, ect...

 

If you search online you'll find specs for head gaskets which includes compressed thickness and bore diameter. I put 0.032 in for thickness, 4.06 for gasket bore, -19.5cc for piston dish(or valve eyebrow volume), and 0 deck height. This results in 8.98 CR with 64cc heads and 9.55 CR with 58cc heads using stock engine bore and stroke. This will run fine on pump gas if you make a point of filing down any sharp edges in the combustion chambers, the edge around the head gasket surface are often very sharp after machining.

 

Thanks Paul. I've been trying to decide between those FRPP X303 heads and some AFRs. I just wanted to make sure I was staying under 10:1. If I go with the AFRs, do you think I should go 165 or 185? Im just looking for good street performance, no racing. I think they offer them in 60cc so that would be about perfect. Thanks!

 

The AFR heads are sweet but they're twice the price of X303 or the Dart Iron Eagles.. which are cheaper than either but fall between them in airflow. I have a set with 2.02/1.60 valves for my 5.8 build...