Just wondering, when I bought my 65 442 some months back, I was told it was 11.5 to 1 compression ratio. Like everyone else, I assumed the fellow was mistaken, as the car wasn't nearly as lumpy as I would've expected. Anyway, I now have the propane system off and sold, and it's running on gasoline from a jug (still need a trunk floor and gas tank, minor details). Fuel pump and carb and stock intake now installed. This is an F block 455 with C heads. Just for fun, when it was warmed up, I pulled a plug at random and did a compression test. Don't want to do them all as it runs the battery down. Anyway, the cylinder came up quickly to exactly 200 pounds compression in about 4 seconds. so I stopped.
My question is this: Do we have any way of guessing what the compression ratio is, or might be, from the clues we have?

 

The manual lists 10.5-1 as the ratio for the 425 4 bbl but it does not list the 400 engine which I believe came in all 65 442.

 

This engine has been changed. The 400 is long gone and someone put an F block 455 in it with C heads. The Jetaway is also long gone. Currently running a Turbo 400 tied to a 12 bolt Chevy posi.