Timing tab

  • GMC
I have a 1985 GMC Short bed pickup with a 305 in it. Trying to read the timing mark directly under the water pump is unreal. I took off the fan and water pump pully, all the belts, shroud. It has 4 V notches. Where is "0" and 4 degrees BTD? There is a very wide notch towards the drivers side. Is that zero?

Thank you,
Do you
have the same problem?
Sunday, March 26th, 2006 AT 5:06 PM

1 Reply

Hey snowman, I'm not positive that gmc and chevy use the same, but if they are tdc (0) is the second point- not notch- from the drivers side going counter clockwise.4 degrees before would be the next point, the v-notch in between would be 2 degrees. See how it goes? The first point would be 4 degrees after. Next point 0, next point 4 before. This is on chevy but should work for you. And your right-It's a royal pain@$ ##$ to see sometimes! I don't know about wide notch unless someone has filed it. Look closely and clean it off real good and you might find
0 marked on it. Hope you get it. Burr

Me again, a little more checking around and I see that on some the wide notch is indeed 0 then it still goes 4 degrees for every point from there. Later
Was this
Sunday, March 26th, 2006 AT 8:32 PM

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