Quote:
Originally Posted by Frank Miller
Not an 8ba because the distributor is times to the crank with a light. The earlier motors it might be a problem because the distributor is timed on a machine and fitted to the cam. You've raised a good point thought about how changing the cam timing might change the engine timing.
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What he is probably talking about is that by having too much backlash, this allows the camshaft to move in/out by more than Ford intended (in the discussion, another .010 or so). The "normal" backlash is around .004 to .007, so by increasing the backlash, your allowing cam timing to change/move and the same with the final ignition timing.
To give you an idea about how this is important, on a recent 383 SBC build (high horsepower street engine), when we had it on the dyno, we noticed that the ignition timing was moving around by about 3 - 5 degrees - when it should have been at a steady state. It so happened to have an adjustable timing cover (nice Cloyes piece) - where you can externally set/control the backlash of the cam.
We tightened down the cam button just a bit and the timing then steadied as it should have. What started our checking was that we were getting inconsistent dyno pulls - HP was fluctuating about 15 - 20 HP . . . we needed to figure out why. The 'why' was the backlash. Now to bring this in context, this engine makes 520 HP . . . more than 5 times a stock 59AB.