Originally Posted By: Hunterdude
I have since learned that the 477 head will have about 6.5:1 compression and the 819 head 8:1 compression.


Are you referring to the published compression ratios?

We'll need to get a little deeper then those to get an accurate estimate. Here's a thread from Inliners Engines Forum circa '12

Deuce Coupe and others discuss the calculation - DC is backing into the combustion chamber and dome volumes based on the published C/R for the 270.

AFAIK the stock compression ratio for the 270 was 6.75:1. This is with a ~130cc combustion chamber, ~31cc dome, an ~.050 compressed gasket and a roughly ~.03125 deck (deck = Deck Height – Stroke - Rod Length – Compression Height).

If you add in the additional displacement (up to 304) – remove the dome – and tighten the deck to ~.015625 you are in the neighborhood of 5.8:1

That's why I would measure the actual head that is bolted to the block to see if it has been milled. With an accurate measurement of combustion chamber volume and deck, the static C/R calculation will be more accurate.