How to set timing on Chevy


Old 12-05-09, 02:30 PM
Thread Starter
Join Date: Nov 2002
Location: MI
Posts: 127
How to set timing on Chevy

Hi all.
I had a post here a short while ago about some problems with my truck. I have them mostly worked out now, but have to set the timing on it.
89 Chevy Silverado, 350, auto trans, 4 wheel drive, TBI.
I tried to research how to set this, and have found too many answers that differ. From 4 degrees to 20 degrees btdc. There is no vacuum line to unhook and some sources say to just set it as is, and some said there is a tan wire that needs to be unhooked and could be under the dash or under the hood. Soooooooooo...

I have a timing light. I found the groove on the harmonic balancer. I found the tab with the timing marks, but can't read them clearly. There is a larger indent that I assume is TDC? Then there is a point with a 4, is this 4 degrees before TDC? Is the next point 8 and the final one 12?
What do I set this at?
Is there a wire that I need to unhook?
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Old 12-05-09, 03:38 PM
Join Date: Jun 2008
Location: Eastern Georgia
Posts: 486
The timing should be at 8 degrees btdc if I recall correctly. You need to find the timing connector, this is a single wire connector that breaks out of the main harness either near the distributor, or near the firewall around the AC drier on the passenger side. Start the truck, disconnect the connector, the engine should change speed when you un plug the connector, set the timing to 8 degrees btdc, turn off the engine then reconnect the connector. Your interpitation of the timing tab is correct big indent is 0 and then 4 degrees per point. After you set the timing if the engine feels "lazy" you can bump the timing up 2 or 4 more degrees and see if it helps, dont go past 4 or you run the risk of causing a hard start when hot condition.
Old 12-05-09, 09:54 PM
Join Date: Nov 2009
Location: VA
Posts: 54
Points above the large indent are BTDC, below large indent are ATDC.
Old 12-06-09, 02:29 PM
Join Date: Dec 2002
Location: Pittsburgh, PA
Posts: 553
What Twister said....

Wipe off your timing indicator and put a little white chalk in the TDC groove, you'll see it easier. Be sure that you are clipped on #1 cylinder with your light. I know it sounds simple but I have seen others do it wrong. #1 is drivers side front.

Your best timing is where they specify or a degree or so higher than they say. Too high like twister said will cause it to feel like it wants to kick back on a hot start. you'll also start to ping.
Old 12-07-09, 07:50 PM
Thread Starter
Join Date: Nov 2002
Location: MI
Posts: 127

Thanks for the info guys. I found the wire to unplug, and it is in fact a tan wire with a black tracer near the air conditioner drier. The timing groove wasn't even showing at first. I set the timing at 12 degrees and what a difference it made! Now the truck is actually drivable ! I am going to set it up a couple more degrees since there is still a touch of flutter when I accelerate.
Thanks again for the correct info. There certainly is no shortage of info out there, it's just a matter of finding the proper stuff.

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