What is the compression ratio of these 440 piston with either 452, 250 or 906 heads.

thanks trying to get lower compression, for a 1969 "block date code" standard bore 440 I just bought that has low miles on it.



Thanks Kurtis

I'd Google em & see if you can find the compression height & compare that to the CH of what's in there now for a guestimate but for accuracy you'd want to measure the deck height when you pull the heads & plug it all into KB's CR calculator. I'm assuming it is pinging now & no interest in running more octane? A custom Cometic THICK gasket would likely take care of it without haaving to go into the shortblock

what head gasket would get me around my target compression ratio?

Thank

I'd say ~9:1 CR for regular 87 octane gas/open chamber/no quench. That'd let you run a quick curve. To answer your Q you'd have to plug in all the required specs into the KB calculator to see what you're at. EDIT I reread & are you sayin the 667's are in there now & you have 906/452's now or do you have 915's & are considering 906/452's to lower the CR? same deal you'd wanna pull the heads & measure the deck height & could lookup the nominal CC's of the 906/452's & plug it all in & go from there. The thickness of the outer head bolt hole boss is within a few thou of 1" on unmilled heads and curved swirl marks on the deck tell you that the heads have been milled (or not) so you may or may not want to CC em for an accurate CR number. That in turn will tell you how thick of Cometic to order & possibly a regular blue Felpro will be enough. I'm assuming your timing (initial/springs) is in the ballpark

I have a couple sets of 1975-1977 pistons but I honestly haven't seen a pre 1974 engine that didn't need bored.

I would take that block to a (trusted) shop and have the cylinders checked before buying anything.

I have stock 906 heads or 452 heads for the 440, and its is standard bore no ridge on cylinder walls.