Vacuum advance
04-16-2018, 05:34 PM
#1
Racer
Thread Starter
Vacuum advance
A friend was checking my timing today, at idle 750 rpm it’s 9/10, when we give it gas upto 2000. Rpm it gets to 20. Is the distributor supposed to be hooked up to the carb plate to pull vacuum. Ian
04-16-2018, 05:42 PM
#2
Team Owner
Nobody can tell you much if you dont even mention the engine. You’re working on. But no, vac advance should be plugged when setting initial timing at curb idle.
04-16-2018, 05:49 PM
#4
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Yes, disconnect and plug the vacuum line (not the dizzy can, the intake port) to set dizzy starting and centrifugal advance timing.
Your buddy should know this if he has a timing light?
If you want to know total centrifugal advance, pull one of the springs and it will come in at lower than spec rpm. This is good to know before you get around to total advance adjustments.
Your buddy should know this if he has a timing light?
If you want to know total centrifugal advance, pull one of the springs and it will come in at lower than spec rpm. This is good to know before you get around to total advance adjustments.
Last edited by Easy Rhino; 04-16-2018 at 05:52 PM.
04-16-2018, 07:27 PM
#6
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St. Jude Donor '22
3 things affect/control spark timing.
1, base timing set by timing light.
this is what the decal, service manual calls out.
in order to get this the vacuum adv hose must be disconnected.
since the hose is under vacuum, it must be blocked so no vacuum
leaks will affect idle.
2, centrifugal advance.
there are weights and springs that move when rpm changes.
this changes timing. they are rated by how much timing they change and at what rpm. problems arise when the idle speed is too high and
the rpm moves the advance.
3, vacuum advance.
when vacuum is applied to the adv pod/can it moves timing.
this device allows a lot of advance to be put in timing when cruising.
but, when you open throttle/the vacuum lowers/ thus taking out timing so it doesn't ping.
1, base timing set by timing light.
this is what the decal, service manual calls out.
in order to get this the vacuum adv hose must be disconnected.
since the hose is under vacuum, it must be blocked so no vacuum
leaks will affect idle.
2, centrifugal advance.
there are weights and springs that move when rpm changes.
this changes timing. they are rated by how much timing they change and at what rpm. problems arise when the idle speed is too high and
the rpm moves the advance.
3, vacuum advance.
when vacuum is applied to the adv pod/can it moves timing.
this device allows a lot of advance to be put in timing when cruising.
but, when you open throttle/the vacuum lowers/ thus taking out timing so it doesn't ping.
04-16-2018, 08:00 PM
#7
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