vacuum advance, is that thing attached to the side of the distributer, and well it has a vacuum line attached to it, when the vacuum pressure is really great, I.E. foot flat to the floor it pulls the timing to more advanced and hence stops the engine going retarded so you maintain power and actually gain a little more rather than loose, to test it, suck on the pipe with the engine ideling the revs should go up as the advance kicks in, and drop back to normal when its not on, other test is rev the motor and stick your finger over the pipe and feel the sucking, or listen for it.
Jason
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I did put something here, but it vanshied, I think
Sorry to pull you up on this dellboy999, but vacuum advance only works at part throttle openings( eg. cruising down the freeway, light acceleration,etc). This is when your vacuum is at it's highest. It gives you better fuel economy and response down lower in the revs. When you floor it, the centrifugal advance does all the work and gives you your advance curve. You can check it like Dellboy999 said, or if you have a timing light, hold the revs at about 1500, then pull the hose off the dizzy. Your degrees or advance should drop. Exactly how much depends on the engine...Shane.
When you flatten the pedal, the vacuum advance is taken out of action and it will retard back to base timing. At that point its up to the weights to take over and advance based on a curve (determined by springs). If the timing is too advanced, the weights will kick in too early and advance too far causing pinging.
Easy thing to do, retard slightly to get around it.
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88 EA Falcon S
3.9litre CFI
5spd Manual
if i change the dizzy will it make it better? apparently the dizzy shaft is worn, but to do that, i have to remove the gas setup, heater lines and everything, its really packed on top of the dissy, and you cannot see it!
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We live in an imperfect world, but
there is no point in trying to make it perfect, because not everyone can be GREEK!
XE Fairmont Ghia... Silver/Grey Met over black, soon to be v8, cant wait till i get another v8, after 3 LONG HARD YEARS
You dont need to Replace the dizzy.
Just get your timing done.
Also can spray some water in the intake while holding the engine at 2000-2500 rpm.
The water will help clean out any carbon build up in the chamber. Which can also cause pinging.
If the shaft is too worn, it will create a vibration, and also make the weights kick out faster causing advanced timing. If its that bad, just get a 2nd hand unit from the wreckers for cheap.
And as VBman said.. try those things.. probably help a bit.. just dont be concerned about he chunks blown out the exhaust as the carbon comes off :)
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88 EA Falcon S
3.9litre CFI
5spd Manual
Another thing to try,
make sure that the vacume advance unit isn't getting full manifold vacume as this will cause the distributor to advance to quickly, the vacume hose may be connected to the manifold instead of the carby.
the other thing is disconnect the vacume advance hose and plug it, run about
3 degrease more timing and just rely on mechanical advance, you advance the timing in 1 degree units, take it for a drive and keep doing this until it starts to ping and then retard the timing slightly.
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