More 273 info please!

[273 Commando]

Ok guys, I scrubbed the motor and tore off the heads. I'm not sure what factory domed pistons actually look like but these pistons are definitely aftermarket slugs. They're flat top with 4 valve notches in 'em and stamped 060 on the piston face. Any ideas? I may as well pull the cam and have it profiled to see what it is too. The heads are '64-'65 with the 5/16 oddball intake bolts and the block is dated Dec. 65. Someone who put this together must've purchased a case of orange RTV because it's on everything including the freeze plugs.....dang! As I stated in my earlier post, the cylinder pressure was 160 psi, but I have no idea what the compression ratio is...any clues? Thanks, Ted

 

[66dartgt]

The only true way to know what the CR is - is by measuring the piston to deck height, and by measuring the heads with a buret and determining the CC's. Include the gasket cc's and you can then calculate the CR. Cranking pressure doesnt tell you much because its effected by cam timing etc. If you want to get technical you would also want a cc measurement of the valve reliefs as well.

Having said all of that I did a theoretical calculation based on piston pin height and using a head cc, based on a measurement using a buret. The particular heads were around 60 CC and the pistons were 273 .060 badgers. I dont recall the part number. Anyway the CR calculated to be around 9.8 to one using thin head gaskets .024 or so.