Re: Tarks Timing, was : Vac advance?

["John Stricker" <jstricke@domain.elided>]

Joel,

I really look forward to seeing the pictures.  This has me more than a
little curious.

With regards to the backfiring, did it sound really like a backfire?  Did
you see a backfire out the carb, or were you on the road?

The reason I ask is, are you "certain" that it WAS a backfire, and not a
piece of the gear going through the point where they mesh?

Bear with me a moment.  I have had a timing gear fail on a 345, but I was
lucky in that it happened as I was trying to start it and right after I'd
replaced the fuel pump.  What happened was a piece of the new fuel pump arm
broke off and found it's way into the gears, breaking one out.  This was a
VERY sudden and immediate lock up of the engine while the starter was
turning over, so I knew something was drastically wrong.  I pulled the new
fuel pump out, saw the arm broken, and went into the "OH S**T" mode coloring
the walls of the shop blue from the words out of my mouth.

Back to something that more relates to you, On a Massey Ferguson tractor
last year, I had a 3/8 bolt break off that holds a retainer in on the
planetary gear set in the rear end.  This found it's way into the planetary
set (simply straight cut gears, three small running inside one big one) and
the damage was so violent that it threw me out of the seat of the tractor (I
was in a cab), broke the bull gear (about 24" in diameter, 4" wide, and 2"
deep) AND the axle housing (a casting weighing about 300 pounds).

Diagnosis on the telephone or over the internet is kind of like an
illiterate man leading a blind man to an unknown address, but what the heck,
at least the price is right.  My guess would be that at some point, you
broke a tooth.  Or two.  Eventually, one of them got itself into the mesh
area, and that was your first backfire, possibly causing the fracture you
see.  It probably didn't take long before it finally gave way and you ended
up with what you have left.

It would not be unusual for a hardened gear set like a timing set, to fail
just the way you described.  They will crack and break out before they wear
out, given that the bearings supporting the gears (in this case, the cam
bearings and main bearings) are sound and have not allowed too much backlash
or gear pull-in to occur (not very likely in the case of a timing set. Or,
of course, the lubricant hasn't become contaminated with metal particles
which WILL cause rapid and extreme wear.  And which may very well have
occurred after the initial breakage as you had an area that was undoubtedly
wearing very quickly.

I am looking forward to the pictures though.  I bet that the majority of the
major damage will be fractures though.

These gears ARE NOT indestructible, as you found out the hard way.  But
much, much more reliable and trouble free than a timing chain set.

John Stricker
jstricke@domain.elided

"I didn't spend all these years getting to the top of the food chain
just to become a vegetarian"