gm 350 timing marks


Junior Member
Central Pa.
My '82 chevy 350 has an irregular sawtooth timing matchmark. There is no zero nor is it callibrated in deg. I'm looking for 8 deg BTDC. I have several manuals but no pictures. Need help.

paul soccodato

Senior Member
westchester ny
clean off the timing tab to see the numbers on it. the balancer has a groove in it. put your timing light on and line up the groove with 8 degrees btdc. or i you have a timing advance light put the light on 8 degrees and line the groove up with zero on the timing tab.
Do you mean by "irregular" that there is one deep notch, and it's not really in the middle of the tab, and then notches and peaks on both sides of the big notch?

The really deep notch is top dead centre (TDC), and the marks towards the passenger's side are BTDC marks.

The first peak (pointy-out part) is usally 4 degrees BTDC (the 2 degree mark is 1/2 way "up" the "ramp" to the first "peak."

The next peak is 8 degrees BTDC. The 6 degree BTDC mark is the notch between 4 and 8 degrees.

On all my tabs that are like this, the maximum BTDC mark is 12 or 14 degrees. At the other extreme, the tab goes to about 6 or 8 degrees ATDC (after top dead centre).

Sorry, I couldn't find a picture that showed the tab either.

Hope this helps.


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