Vac Advance
Melting Slicks
Joined: Oct 2006
Posts: 2,417
Likes: 336
From: Texas
look at designation 'A' in the diagram. front ,throttle side on qjet
http://willcoxcorvette.com/instructi..._hoses_l82.jpg
http://willcoxcorvette.com/instructi..._hoses_l82.jpg
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,618
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From: New Or-leens Loo-z-anna
look at designation 'A' in the diagram. front ,throttle side on qjet
http://willcoxcorvette.com/instructi..._hoses_l82.jpg
http://willcoxcorvette.com/instructi..._hoses_l82.jpg
Thanks for bailing me out
!
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
What fitting you WANT the vacuum line connected to might be different than where GM put it at the factory. In '69 or '70, the line going to the vacuum advance canister came from a "timed" or "ported" vacuum fitting. The concept was that at idle, the engine should be retarded so that it created less polutants...even though it wasn't best for the engine and caused it to run hotter.
So, if you are a really 'green' person, leave it connected to a "timed" fitting. However, if you want a better quality idle that is also better for the life of the engine, connect it to a "manifold" vacuum line.
If you have yearly emissions testing requirements in your state, you may want to put it on a timed fitting for doing the emissions test, then move it over to a manifold fitting for normal driving.
So, if you are a really 'green' person, leave it connected to a "timed" fitting. However, if you want a better quality idle that is also better for the life of the engine, connect it to a "manifold" vacuum line.
If you have yearly emissions testing requirements in your state, you may want to put it on a timed fitting for doing the emissions test, then move it over to a manifold fitting for normal driving.
2026 Loser of the Year
Joined: Sep 2013
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From: New Or-leens Loo-z-anna
Good to know!
Rookie answer about running hot: If the timing is set very high----then lessening the timing can help it idle at a cooler temp
If the timing is too low---the engine temp will increase.
Last edited by doorgunner; Feb 16, 2014 at 03:34 PM.
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Retarding the timing at idle (by artificially blocking off the vacuum advance signal) makes the engine run hotter. And a hotter combustion chamber results in less pollutants. At least, that was the concept.
But the idle quality was poor and the emissions system had to include a 'failsafe' system in case the engine ran TOO hot; so there was a HI temp switch that cancelled out the vacuum advance 'defeat' system. If the car idled too long and reached excessive temps, the vacuum advance was restored until the temp dropped to normal values.
But the idle quality was poor and the emissions system had to include a 'failsafe' system in case the engine ran TOO hot; so there was a HI temp switch that cancelled out the vacuum advance 'defeat' system. If the car idled too long and reached excessive temps, the vacuum advance was restored until the temp dropped to normal values.
2026 Loser of the Year
Joined: Sep 2013
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From: New Or-leens Loo-z-anna
Man! GM solved problems.....
but created more problems....
then solved the created problems.....
leaving intermittent problems....
which solved each other........temporarily.
I think I've got it now!
but created more problems....
then solved the created problems.....
leaving intermittent problems....
which solved each other........temporarily.
I think I've got it now!
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,618
Likes: 7,068
From: New Or-leens Loo-z-anna
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