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AKMark
05-11-2007, 09:18
I just finished up and got my 91 running. I rebuilt the motor thanks to a connecting rod cap failing and causing some issues. The motor did have 238K on it when this happened, so no big deal.

Bored it .030 over and reassembled, everything seemed okay. However looking back, the crank turned nice and easy with only the pistons on it. When we put the timing set on, it went from turnable by hand (no heads) to hard to turn even with a flywheel wrench. This was before the lifters/pushrods/rocker arms were installed. I am regretting that we didn't look it over after finding the cam so hard to turn.

While returning home yesterday, it went from running perfect, to dead in no time flat. Just died, without warning. I attempted a restart to only to find the starter spinning really fast as well as the fan. I think the timing chain snapped.

Early next week we'll take it out and tear back into it and verify that's what happened. With less than 200 miles on the motor, we're hoping that the timing chain or cam has a warranty.

john8662
05-11-2007, 09:40
Perhaps the cam gear for the timing set didn't fully seat on the cam causing the chain to have an alignment issue and bind?

Was the cam easy to turn by itself when it wasn't connected to the timing set?

Were all the plugs in place before the set was installed (mainly the back cam plug)?

Turning really fast w/o the valvetrain moving could be very dangerous for the engine, hope there were not open valves in the event the chain failed.

What brands of components?

J

DmaxMaverick
05-11-2007, 09:44
The cam or crank key will shear before the chain snaps. It's designed that way.

There should have been little, if any, difference in turning the crank with or w/o the cam in place. That would have flagged me. I hope you got lucky when the stop happened. Off-timed valves can destroy themselves and pistons in a hurry. If it spins, and you aren't hearing any knocking/clanging, you are either lucky, or damage has gone too far. Interesting though, a cam bad enough to feel should not have installed easily, if at all.

We can spend a lot of time speculating and get nowhere, so a look-see is in order. Let us know what you find.