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#43497 02/08/2004 3:49 AM | Joined: Jul 2003 Posts: 101 Wrench Fetcher | | Wrench Fetcher Joined: Jul 2003 Posts: 101 | GMC 302 motor. Mechanical advance. 2 bbl carb (Holley I think)
I've read a few posts that suggest setting timing with a vacuum guage so that you have the highest vacuum at the highest RPM. I tried this today. The RPM and vacuum (18 lbs) stayed the same over probably an inch of movement of the distributor. After the initial setting it pinged so I turned the distributor clockwise until it stopped. It took about four tries and I probably rotated it 1/2 inch.
Am I doing this right? I don't see how you can set the timing with a vacuum guage when the vacuum and RPM stay the same over probably 20 degrees of rotation of the distributor. | | |
#43498 02/08/2004 4:04 AM | Joined: Oct 2003 Posts: 70 Member | | Member Joined: Oct 2003 Posts: 70 | You set mixture with a vacum gauge at idle I have never heard or done it the way you are taking about, I always set timing on my own stuff like you did back off till it stoppes pinging | | |
#43499 02/08/2004 4:30 AM | Joined: Jul 2003 Posts: 101 Wrench Fetcher | | Wrench Fetcher Joined: Jul 2003 Posts: 101 | I didn't mean to imply that this test was done at high RPM; only that the vacuum and idle RPM both were supposedly highest when the timing was correctly set. | | |
#43500 02/11/2004 5:47 AM | Joined: Jun 2003 Posts: 56 Member | | Member Joined: Jun 2003 Posts: 56 | Izz,
Warren is right, you set idle mixture with a vacumn gage, not timing. Do the timing first, then the mixture with a warm engine.
'31 Chevy 1 1/2 ton,
'42 GMC 2 1/2 ton 6x4,
'52 GMC 2 1/2 ton 6x6,
'53 GMC 5 ton
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#43501 02/11/2004 6:09 AM | Joined: Jul 2003 Posts: 101 Wrench Fetcher | | Wrench Fetcher Joined: Jul 2003 Posts: 101 | I actually had pretty good results setting the timing with a vacuum gauge. I'll admit that the initial timing with the vacuum gauge was far from precise, but in the process I did learn how to time it by ear by retarding until it stopped pinging. I also noticed a significant increase in power from where it was previously set. | | |
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