My truck has been running rough so I decided to check my ignition timing to see if was right. With the #1 cyclinder at TDC (verfied by placing a screwdriver in the spark plug hole) and the distributor rotor pointing to the #1 spark plug wire terminal, I was surprised to see the timing marks on the crankshaft pulley are at 16 degrees BTDC. It SHOULD read 0 degrees TDC. I pulled the timing cover off and the alignment is correct between the camshaft and crankshaft gear timing marks. So, everything lines up like it is supposed to but the timing marks on the crankshaft pulley read 16 degrees BTDC. What the heck is going on here?

It was overhauled at a garage about 20K miles ago and has run like crap since.

 

They probably used the timing mark to set it, and it's obviously wrong. The mark is stamped into the outer ring of the harmonic balancer, which is pressed onto the hub with a rubber strip between them. Over time, the outer ring can slip on the rubber, causing the timing mark to wrong. Make a new mark where you KNOW 0° is and use that to set the time.

 

Steve83.......Thank you, thank you, thank you!!!! I've been scratching my head for a week on this one. Sure enough, the harmonic balancer has slipped and I have been using the timing marks to set the timing assuming the timing marks were accurate. That explains why it has been running so crappy for the last few years. I never would have figured this one out. Again, thank you for taking the time to help me out. What a great web site this is!

 

Aftermarket harmonic balancers are getting cheaper. Price a lifetime one from a few parts stores - they're not hard to change.

 

If you remove the 15/16" bolt in front of balancer, you will see the shaft key, you can use it as a guide to punch a new timing mark in the outside ring of balancer.

Regards.