Well, I wrote the changes needed to get the stock ZZ distributors working correctly, but not many seem to care, they use all sorts of idiocy from top tuners and dyno experts to make it even worse. IF those mods are not done, the engine will never wake up, no matter what you do to it.
Weights 41, center 375 stock parts are FINE, the springs are the problem. This package gives 22 crankshaft degrees of mechanical advance timing. But, because GMPP set all the specs on a dyno, they left the distributor on PORTED vacuum, dead wrong for that engine. What that did was give the engine no light to no load timing help, and create a second acceleration advance curve. To compensate for the second curve, the mechanical was set up with garage door springs, starting the curve at 1,300 or so RP's, and limiting the curve way past 5,500 RPM's, way too allow for real world performance.
Fix, speed up the mechanical curve, use springs toat start at 850/900 RPM's, limit at 3,000 RPM's AND SET THE VACUUM ADVANCE UP CORRECTLY TO USE FULL MANIFOLD VACUUM, NOT PORTED. Doing so will give that engine the acceleration advance curve it wants.
Vacuum advance: either use a Crane 99619-1 stand alone degrees stop plate, or a home made degrees stop plate to limit the degrees the 69120 vacuum advance has (full FREE instructions, with pics available at [email protected]
) to limit the vacuum advance to give 10 degrees of timing. Then, along with the 11/12 initial timing the ZZ has, add the vacuum advance degrees to FULL MANIFOLD VACUUM sourcing to get 21/22 IDLE degrees of timing.
Fix whatever else in the carb that was messed up with the ported vacuum stupidity, and go forth.
YES, a different duration cam will require different timing specs, but, with the Crane stop plate installed, they are easily arrived at.
But, nope, nobody here knows anything about stuff like timing, fat and skinny block engines, tuning, carbs, we are all dummies, and drones.