Hi there. I'm building a .40 over 455, JE flatops. There sitting in the hole .60''. I'm running the TA aluminum STG 1 heads,with a .40'' orange crush gaskets. My question is how much compression approx. will I have if I deck the block .30'' Getting some confusion with my engine builder, they can't seem to give me an accurate compression valueo No: Any help with this would be greatly appreciated. Would still like to run pump gas or pump gas/race fuel mix. Thanks Jim
I punched your problem into the DeskTop Dyno and here's what I came up with: What is the size of the head's combustion chamber? If you have a 72 cc head, your compression is right around 10.8 to 1. If head is 69 cc's, your compression's 10.96 to 1. It will keep going up or down in a similar fashion, theoretically.
Thanks Phillip, TA advertizes the heads having a 64 to 66 cc chamber. So I guess that will bump me up into the 11.5 range? That would still be fairly streetable I would think.
Jim, A machine shop should have no problem accurately figuring your compression. I just had my block decked and the only information I had to give the shop was the compression height of the pistons, the head cc's, and the cc's of the gasket. Of couse the block and 1 rod with piston attached. The aluminum heads are advertised as 64 - 66 cc's and the Orange Crush gaskets are 10 cc's (approx maybe 10.2 cc's to be exact). Call the place you got the pistons and ask for the compression height and how many cc's the valve reliefs are. I am running (or will be when the heads come in) Stage 2 heads (same cc's as Stage 1), Bill Miller pistons (TA used to carry), Orange Crush gaskets and I have 12.2 - 1 compression with the pistons approximately .020 in the hole. Hope this helps. Tom Jenkins
If you have a steel rod and your cylinder head has a quench area you better get a thinner head gasket or deck the block. With the piston .030 in the hole and a .040 gasket that give you a .070 quench which is terrible. With .070 you will lose a significant amount of horsepower, (about 7% - 8%) and the engine will be more prone to detination. I assume your rod is 6.60 so I would try for a .035 quench. This will be much more friendly to pump gas and make more power. Ever wonder how the new model engines are making so much power. Well one reason is quench, as most have about a .030. By the way if you want to find your compression ratio go to: http://www.campbellenterprises.com/Race math calculators.htm Blair
A 66 to 64 cc chamber yields a compression ratio range of 11.45 to 1 to 11.68 to 1. I would have to say that even with aluminum heads, you are pushing passed the "pump gas" compression ratios. I would definitely polish everything up (combustion chambers and piston tops) as best you could to help eliminate detonation problems and hot spots. You may still need to add a couple of gallons of 110 octane per tank to eliminate it. Good luck.
the quench theroy is correct. if it was my engine and it wasn't balanced yet i would 0 deck block and have a dish machined in pistons to get no more than 10.5 to1 on pump gas . the large bore is detonation prone. detonation blows more engines up than anything.. Rod Hendrickson.
Scott, not sure what cam to run yet, was planning on using TA's 310 or 413 both are fairly close. And Ron, the rotating ass. has already been balanced. I do have full intentions of running a mix of pump and race fuel if required, not a problem here. thanks Jim
