Help identify aluminum heads
Took awhile but finally pulled the pan & confirmed its an eagle 4.150 stroke crank. So I guess that makes it a 493 but what does that do to the compression?
Well, the longer the stroke, the higher the the compression for a given combustion space size.
As PRH said, until the heads come off and some actual measurements are made, we won't KNOW what the compression ratio is .
However with a little more info, we could make an educated guess. The first thing we would need to know, that we don't know, is the compression height of the pistons. Call mahle with the work order number if it's not on the box. They will know.
That would at least give us a reasonable guess as to deck height. Consider: a flat top engine like yours at zero deck, with true 75cc heads is probably a 12 to 1 engine. If the pistons are .150 down in the hole, (as some oem 440 pistons were) it would probably be a mid 8 to 1. But without some idea of deck height, no calculation will be any better than a complete WAG, wild *** guess.