I recently was adjusting the timing for my 1989 Chevy S10 4.3L engine. During the process, I realized I don't know for certain which mark or notch designates the 0° mark, and I can't tell if there is an engraving that I missed. If anyone knows for certain, please a take a look at the photo and provide input. It seemed to be around position E or F.

Thanks

 

Deep notch should be 0, link.

 

yeah the big valley you labeled F is 0. and each up and down point is 2 degrees

 

I'm not quite there yet but I'll likely have to set the timing on my son's 85 Chevy S10 with a 3.1 (out of a 91 Camaro). I've been wondering which groove on the harmonic balancer is going to be the correct one to use as zero. It has (technically they both have, 2.8 stock & 3.1 going in) two thin grooves and one fat one. So far the best answer I've gotten is to bring the number one to top dead center and the groove under the 0 on the timing guide is the correct mark.

 

Position F worked for me with the 4.3, not sure about the 3.1.

 

IF I'm not mistaken, (I've slept since I looked last), the timing gauge on the 2.8 timing change is marked with 0 and the degrees. What I'm not sure about is which mark to use on the harmonic balancer. Not sure it'd be the same as on a 4.3 though. That'd be too easy.