timing chain - 91 Sub

Did you unplug the ESC wire before checking timing? If the answer is yes, and the idle was steady then yes it's a good guess the timing chain is stretched. Given the mileage it's due anyways, and always do gears and chain as a set, and dont get cheap with the replacement parts.

Whitelightning

Water pump?

How can a bad water pump cause the strobe timing marks to be jumping around? Can't see it.

No I meant if you do the chain and gears do a water pump too. Unless GM has relocated it.

You're there anyway.

Whoooooooooooooooooooooosssssssssssssssssssshhhhhhhhhhhhhhhhh!

OK..I get the stupid prize for today....

LOL no problem.

Yes, picking up a new water pump is a great idea. I would grab a harmonic balancer repair sleeve as well. It is always nice to have everything ready when you start tearing into it. You can always take the sleeve back if you dont need it, after you are done with the job. When I changed my timing chain on my 94 ck1500 with 220,000 miles, it needed a repair sleeve. since you are going to loose alot of antifreeze, it might be a good idea to completely drain and refill with fresh antifreeze and distilled water. Antifreeze becomes corrosive over time. Be absolute certain to unplug the little wire before checking timing like WhiteLightning said previously. The wire was located at the passenger side fire wall just behind the black plastic cover on my 89 ck1500, it was under the glove box on my 94 ck1500, if i remeber correctly it is a single brown wire with a black trace.