Midget,
Post of "chicken scratch" note sheet from my 4/26/2012 foray to "Cheddarslovakia".
Note that there are some corrections,
in red, to the original #'s. I'm going to maintain my allegiance to sliderules & calculators.........
Note that the closest point for the exhaust valve/piston is @ 2 degrees BTDC and for intake valve/piston @ 22 degrees ATDC. If these are factored by the amount of cam retard in degrees
(12.75), they become 14.75 BTDC/exhaust & 9.25 ATDC/intake. This roughly corrects to 3 degrees camshaft advance, as opposed to the 4 degrees APT specifies for this cam.
Splitting the overlap period straight up (no advance/retard) becomes 12 degrees BTDC/exhaust & 12 degrees ATDC/intake. This is definitely a function of build geometry, ie: rod length/stroke ratio of 2.45/1. Closest point of valve to piston would normally be 8/10 degrees ATDC/BTDC for rod ratios of 1.6~1.7/1.
The resultant piston dwell, around TDC, of the long rod/short stroke geometry, is going to be a limiting factor for not only cam timing, but more importantly, how quickly the inlet valve can be accellerated to full open.........
The most disturbing issue here is that it is the end cylinders that are ground on 106 degree lobe centers & the centers are on 102 degree lobe centers. This will
REDUCE the valve to piston clearance on those (2/3) cylinders,
IF, the lobe is the same for every cylinder. (unknown)
Need to put my slide rule in the freezer.........
Egghead Jr.