Check my work-Chime in please
Hold the phone everyone.......the data given is not complete enough. You can't just calculate CR from the apparent 2.4 cc's measured above-deck volume, because there is also below-deck volume at TDC. The reason I say all of this this is because the Egge dome volume in not 2.4 cc's, (which is the flat-top .500" down-in-the-hole volume minus the measured down-in-the-hole volume). There is some volume info that we are missing.....
DR, how did you measure how far down in the bore the piston was when you did the in-block cc-ing? Did you use a dial indicator or a caliper or? And did you measure from the flat top of the piston for the .500" or where? This accuracy and where you measured is critical to your results. (And did you seal the edges of the piston top with clay when cc'ing .500" down in the hole?)
How far down below deck is the flat part of the piston when at TDC? We could work from the Egge compression height number but any block decking info would be missing from the equation.
Your cam closing number looks incorrect. I am getting 56* ABDC; that is based upon the advertised cam specs.
what measurement is missing? As far as i can see it's all there.
A perfect cylinder of 3.665" diameter is 0.500" height = 86.359cc (86.36)
This cylinder has a dome to reduce chamber volume, but it also may be slightly down the bore at TDC, not to mention it has ring lands, valve recesses etc that will add to the chamber volume. all of which mean that when the piston is moved .500" down from TDC and then a plate is put over the deck the measured volume is going to vary from the theoretical perfect cylinder volume of 86.36cc. the difference, be it negative or positive is added or subtracted to the effective combustion chamber volume.
In this case, the volume of that cylinder is a measured 84CC.
86.36cc - 84cc = 2.36cc (for simplicity sake we call this 2.4cc)
That's a measured volume, not guessed or taken from a parts book advertisement.
What numbers are we missing? We have calculated both the above deck volume and the below deck volume at the same time using the .500" method and come up with a final number of positive 2.4cc.
subtract that 2.4cc from the cylinder head chamber volume and you have the total chamber volume. 60.1cc.
factoring in gasket volume and cylinder's swept volume, all the numbers are there. right?
Having the advertised numbers, I also got a IVC at 56 degrees. bringing my calculated DCR to 8.15:1 at sea level.