I just bought a used motor w/137K miles from a junk yard to install in my 99 Tahoe. I was about ready to drop it in when I notice the timing has been advanced 1/4 to 3/8’s of an inch. Does this probably mean what I think it means? The timing chain has probably jumped a tooth and needs to be replaced before I drop the motor in?
Camshaft and crankshaft sprockets
The engine timing is not adjustable. The cam retard offset will not be accurate below 1,000 rpm. What this means is, you cannot check the actual timing without it running. If you are just looking at the timing chain gears and they do not line up dot to dot, then inspect the camshaft and crankshaft sprockets for:
- Broken teeth (1)
- Damaged teeth (2)
- Chipped teeth (3)
- Worn teeth
- Uneven wear on one edge of the teeth
- Worn valleys between the sprocket teeth
- Crankshaft sprocket keyway for wear
- Crankshaft sprocket woodruff key for wear or damage