04-12-2005 04:15 PM #1
Compression specs of 360/390
Going to swap a 360 for a 390 at city motor supply tomorrow. I'd like to get the one that has the highest compression from a rebuilder. They are going to give me a "torquer" cam to put in it for $70 extra.
What are the stock compression ratios of the 360 that came out of my 73 ford truck and the 390 that I'll be putting in.
Being they are the same price. $800ish I like the idea of having the longer stroke of the 390.
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Stock compression was kinda low in the 70's. Something like 7.4:1 on the 360 and 7.8:1 for the 390 on truck engines. Early trucks with the 390 were around 8.5:1 and most 390's in cars were 9.5-10.5:1. This is from memory so please double check these but should be close. G.
I picked up a 390. The silv-o-lite pistons they use in it are rated at 10:1. I'll CC the chambers and cylinders to see what I've got. I'm just gonna polish the chamber, sand sharp edges on the piston reliefs, and maybe do a little bowl blending before I bolt it all together. Maybe that will help to prevent detonation at the higher compression being it's going into a truck.