Higher compression octane requierments
How are you measuring dynamic compression ratio? Are you sure, for a fact your CR is that high. I'm asking, did you actually measure dome volume, chamber volume, gasket volume and do the math?
If you didn't, you don't know what you have. Usually the CR is much lower than advertised. But you could easily be off a point or more either way.
11:1 on pump gas is relatively easy to do.
Everything was measured, and
everything is known. The worksheets are not right here in front of me (i'll grab them), but I
personally made all calculations, checked all clearances and verified all cam timing with a wheel, CC'ed chambers with a burette, and .500 down fill for dome volume, gaskets are very thin Cometec units, etc, etc. I mocked it up several different ways to see which is the proper direction to go, and what is
too much for iron heads, in all practicality. The static is over 11.5 to one with the block decked and the 915 closed chambered heads shaved, pretty close to what the ancient catalog said they would be, and the dynamic is a true 10.0 to one, as according to the cam timing.
But you make my point in
asking the question in the first place. So many motors are built with relative known parts, and
it works out just fine. But, and this is a big one, there are large numbers of folks that are running by the seat of their pants, and don't know for a fact what the dome is, the chamber volume is, the critical valve clearances, the actual minimum gas requirements, yada, yada, yada, then want to comment but are kinda scratching their heads. I'm trying to learn
where the edge is, NO GUESSING. I had hoped cranking pressure would tell us something,
as an added layer of dimension to the puzzle. Thx again to all who have jumped in on this thread, I appreciate the voice of experience!! Lefty71
