Timing Gears - Jumping a Tooth

[jlandry@domain.elided (John A. Landry)]

Guys (and gals),

I'd like to say a few words on this business of timing gears jumping a
tooth...

I'm currently rebuilding a 392 in my garage, and after seeing how wide the
timing gears are, how deep the teeth mesh and how little tolerance there is
between the gears, you ain't very likely to "jump" a tooth without some
*serious* and immediate consequences.

For fun, let's just pretend that things in the engine could get sloppy
enough, and something get stuck enough for the gears to want to jump (not
very likely)... you'd have teeth *shearing* off one or both gears or
possibly woodruff keys shearing on the shafts.  I can't imagine the gears
surviving a "jump" by one tooth and then everything else running as normal
(with the valve timing being the only exception).  This is *not* possible!
You'd have serious chunks of metal being chewed up by the gears.  Rather
(as Joel B's example seems to verify), that engine is going to quit almost
immediately.

Why do I bother saying this?  Simple... Never forget the BASICS folks!
Resist the temptation to jump to wild conclusions that tend to draw you
away from simple mechanical troubleshooting procedures.  I'm amazed at how
some folks insist on neglecting basic preventive maintenance and then when
their truck won't run, they start to looking for some bizarre explanation.
All along they simply needed to clean (rebuild) their filthy carburetor or
distributor, etc.  This isn't directed at anyone in particular, but if the
shoe fits!

Sorry... enough ranting!

John L.
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