What are the combustion chamber sizes on the various year 455 heads? All I can find is that the `70 had a 10.0-1 compression ratio and all the rest seem to have 8.5. Was this accomplished through different chamber volumes or different dish depths in the pistons, or both? I have a `74 engine and would like to bump it up to at least 9.5 or more so I need to know if I should find earlier heads or if I can make it up with the `70 style pistons. Thanks.
It's mostly done with pistons. I have a '73 block...the pistons look like bowls you could eat serial out of.
Some early Kenne Bell info I have states '70 heads were 69cc, and 71-74 heads were 71cc. These were averages of many heads they had checked. I have cc'ed some Speed Pro 2362P '70 replacement forgings at 23cc. Speed Pro also used to offer a low-comp forging as a '71 up replacement, and I recall the dish being somewhat larger. I can't locate my old Speed Pro catalog to verify, but I seem to remember 45cc on these. So the major difference is in the piston dish. Both of the Speed Pro forgings had a compression height of 1.975" Heads can be milled 0.004" per cc, but be mindfull of piston to valve clearance. I have milled heads to 55.5cc chambers, but this definately required notched pistons.
just mill the heads .030 and assemble with .040 head gaskets(unless you can get the stock repl. ones) the engine will be aroud 9-1 and make alot of power,cam choice dictates compression needs if you stay with a moderate cam youll be fine try and stay under 240@.050 and make sure the check the piston to valve clearence i like the ta 212 cam,nice lope and makes good power. ken
OKay, so if I am having my stock 72 heads milled .020, that should buy me 5 cc in the head combustion chamber and .5 of compression? Not bad
.020 off the block builds more added compression and protects from detonation. Head milling gets less compression change and more detonation problems. The fuel mixture burns better when the flat of the piston is closer to the flat of the head. It squirts the gasses out of the perimiter of the cylinder into the middle at TDC. Builds more power and less detonation problems. Read about zero decking the block on this web site. Good info.
