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#1
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Vacuum advance
Finaly got some extended run time on the eng man she is sweet even moves lol I am running an Edlebrock performer series carb both vacuum ports are wide open at idle if I hook them up I have full advance is there any other options you guys know of .If memory serves me the advance should be ported.The only other issue I had was fuel press gauge reading 0 it's a liquid filled gauge brand new just wondering if the stock pump has enough pressure to make it read ? increments of 5psi.
Thanks for any help |
#2
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'geeto,
If you have a stock type distributor and stock vac advance, it should be connected to full manifold vacuum. Manifold vacuum is usually one of the ports on the throttle body (baseplate) of most carbs I think. Should check it though to be sure.
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Dave http://www.squidsfabshop.com/? (updated January, 2013, Pypes exhaust installation) |
#3
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My vacuum advance is hooked to the back side of my Carter AFB Competiton Series carb. Was the same for the points distributor as it is for the HEI I'm now running. Note: I don't have power brakes so that's the reason it's pluged to the rear of the carb.
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Gary Get in, ShuT Up, Hang On! Member of the Baltimore Built Brotherhood MY GTO built 4th Week of March 1966 "Crusin' Is Not A Crime" Keep yer stick on the ice. |
#4
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I cannot hook my vacuum advance to full manifold vacuum. The car just won't run right. I have it hooked to a ported line on my carb and the engine runs much better. I guess my question is why would one want full advance at idle?
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Remember no one is perfect. Everyone's butt has a crack in it! |
#5
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As far as I know you don't. Not sure if mine is hooked up so it's at full advance or not, but it runs fine so far.
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Gary Get in, ShuT Up, Hang On! Member of the Baltimore Built Brotherhood MY GTO built 4th Week of March 1966 "Crusin' Is Not A Crime" Keep yer stick on the ice. |
#6
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Hey guys,
I went through this when I re-did a whole new quadrajet for my car, and I also completely rebuilt my original points distributor (but I still am using the original vacuum advance that is had.) My QJ is from a 79 Trans Am so I wasn't quite sure what port the distributor can should go to, so I did some internet research. I found various answers, but the best was from a paper purported to be by a "GM engineer". Yeah, I take these sort of things with a grain of salt, but I have to say I found the arguments compelling. For me, manifold vacuum advance works perfectly. My car runs cool, it hasn't pinged yet. It starts so nice too. Don't forget to time the distributor with the vacuum disconnected. Here's the text from the "GM engineer"..... Quote:
__________________
Dave http://www.squidsfabshop.com/? (updated January, 2013, Pypes exhaust installation) |
The Following 2 Users Say Thank You to squidtone For This Useful Post: | ||
#7
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Squid, so he's saying any of the small vacuum ports at the base of the carb are ok for full vacuum.... including the rear port. Maybe even the hollow carb stub too if you have one?
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Gary Get in, ShuT Up, Hang On! Member of the Baltimore Built Brotherhood MY GTO built 4th Week of March 1966 "Crusin' Is Not A Crime" Keep yer stick on the ice. |
The Following User Says Thank You to GT182 For This Useful Post: | ||
#8
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the vacuum advance should be hook to a port that DOES NOT PULL VACUUM AT WOT(wide open throttle) at wot there should b no vacuum at the distributor...that is where mechanical advance comes in
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#9
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At WOT it´s preferable to have no vacuum at all in the intake.
The centrifugal (mechanical) timing advance starts at approximately 1000 rpm and is present all the way. The vacuum advance is an engine load sensor device adjusting the timing depending on engine load. |
The Following User Says Thank You to Kenth For This Useful Post: | ||
#10
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If you have any vacuum at WOT somethings wrong it was that the last cars I worked on with vac advance were smog cars and I remembered them being ported static timing usually run 10 degrees so with the full advance at idle it's running 28 degrees seems to have a sweet spot there what are you guys running total timing with pump gas.Thanks for the schooling refresher course makes sense.
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#11
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Yes, I'm not sure if some carbs may have a port on the throttle body (baseplate) that is actually some other vacuum signal. So I would just be sure the chosen port actually pulls a nice vacuum at idle.
My takeaway from the article is that all contemporary auto engines of the pre-emissions era use manifold vacuum. Good luck!
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Dave http://www.squidsfabshop.com/? (updated January, 2013, Pypes exhaust installation) |
The Following User Says Thank You to squidtone For This Useful Post: | ||
#12
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A hollow carb mount stud like the factory sometimes used is a good place to get manifold vacuum for the distributor. I run both of my GTO's on manifold vacuum, as originally designed. Manifold vacuum at idle allows for cooler running in traffic and better throttle response off idle at low speeds. As stated, it goes away at WOT when intake vacuum drops to near 0, and the vehicle relies on the centrifugal advance. Some cars run rough on manifold vacuum if the initial base timing is set too far advanced.....say at 15-18 degrees instead of 6 degrees. FWIW.....
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Jeff |
#13
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that GM paper is from the team chevelle web site. since there are way more chevelles there is more people there with answers. i have been on that site over ten years. true pontiacs are different that chevies but the answer is to try both and see what works for your application. use seat of the pants or a stopwatch. true one way may run cooler but do what makes you happy in the end. getting your distributer recurved and tuned with the correct springs for the proper mechanical advance is a good starting point.
Jim |
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