Vac advance... - Pontiac GTO Forum
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post #1 of 8 (permalink) Old 10-27-2018, 08:10 PM Thread Starter
 
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Vac advance...

As new owner of 1970 ram air 111,I'm finding some unusual stuff from PO.
No surprise there.
Car seems to be running ok,but as I am about to check timing I found carb port plugged,but dizzy vac tube just hanging.tube was cut.
I've heard of people not running vac advance,but this was plugged only at carb.
Maybe he couldn't tune it?any thoughts.
Thanks,
Bob H
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post #2 of 8 (permalink) Old 10-27-2018, 08:16 PM
 
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There was a post on here not long ago on this subject.i will find it for you. Bottom line you do not want to have a street car without vac advance . Many reason. Drivability . Mpg . Over heating . Just a few .and manny more. This was done on quarter mile race cars with limited success . Doug
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post #3 of 8 (permalink) Old 10-27-2018, 08:22 PM
 
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Hope this link works. Poster Dave Ray is corrrct but that's my opinion only . https://www.gtoforum.com/f170/1968-gto-timing-issue-132423/
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post #4 of 8 (permalink) Old 10-27-2018, 08:34 PM
 
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post #5 of 8 (permalink) Old 10-27-2018, 08:49 PM Thread Starter
 
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Thanks all,I agree,I have no plans to run without,just curious as to why.
It was deliberately cut and plugged.
I'm pulling dizzy to install pertronix.
Did it on my 65 Ford and was and still am pleased with it.
I guess I will find out what needs to be adjusted afterwards?,new to Pontiacs,but I love this gto.
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post #6 of 8 (permalink) Old 10-28-2018, 02:28 AM
 
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"...I've heard of people not running vac advance,but this was plugged only at carb..."

No need to plug the vac can itself. There no vac in it to leak out. It works ONLY when vac is hooked to it.


I never used the vac advance on any drag car. The reason is because at WOT there is not enuff vac for the vac advance to work.

But, a street car needs a vac advance for reasons mentioned. It's especially beneficial under low rpm cruise conditions.

For street cars, it's a good idea to use an adjustable vac can. Some factory non-adjustable cans are said to add too much advance. This can cause pinging & associated problems. I've read that some cans can cause the total advance to be well over 50, under certain conditions.

https://www.google.com/search?q=how+...hrome&ie=UTF-8
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post #7 of 8 (permalink) Old 10-28-2018, 05:31 PM Thread Starter
 
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Thanks,for all the info.
I did remove dizzy,sucked on vac seems like no movement.
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post #8 of 8 (permalink) Old 10-31-2018, 04:06 PM
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You can buy a replacement vacuum advance unit just about anywhere. Be sure to research the application so that you get the right one. These days, with fuel quality the way it is, it is often safer to get a unit that somewhat limits the advance.....say to no more than 10 degrees. I've used the adjustable Crane and Accel units, and the adjustment screw fails the second time you go to adjust them. At least that's been my experience.
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