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Joined: Aug 2009
Posts: 9
Grease Monkey
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OP
Grease Monkey
Joined: Aug 2009
Posts: 9 |
Does the vacuum advance stay connected to the distributor when setting timing?
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Joined: Sep 2007
Posts: 183
Shade Tree Mechanic
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Shade Tree Mechanic
Joined: Sep 2007
Posts: 183 |
Yes, the vacuum line remains connected! There is no vacuum signal to advance when the engine is idling; the vacuum port at the carburetor only allows vacuum to the advance when the
throttle is open beyond the closed idle position. I usually adjust my idle speed to as close to 500 RPM as I can get, then
adjust the idle air mixture screw to the smoothest idle you can get, then set your timing, and readjust carb settings as necessary. Gen Schneider advises setting the'octain selecter'
near the advance about 8 degrees early! I have done that and
it seems to work out very well! Engine starts easily and preforms well! Those Chevies do like some advance!
flip
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Joined: Aug 2009
Posts: 9
Grease Monkey
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Grease Monkey
Joined: Aug 2009
Posts: 9 |
My thanks for that info. There is advance vacuum at idle so I must have the idle rpm too high. Will fix that. Thanks again.
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Joined: Jan 2002
Posts: 1,869
ChatMaster - 1,500
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ChatMaster - 1,500
Joined: Jan 2002
Posts: 1,869 |
Yes, the vacuum line remains connected! There is no vacuum signal to advance when the engine is idling; the vacuum port at the carburetor only allows vacuum to the advance when the
throttle is open beyond the closed idle position. I usually adjust my idle speed to as close to 500 RPM as I can get, then
adjust the idle air mixture screw to the smoothest idle you can get, then set your timing, and readjust carb settings as necessary. Gen Schneider advises setting the'octain selecter'
near the advance about 8 degrees early! I have done that and
it seems to work out very well! Engine starts easily and preforms well! Those Chevies do like some advance! Phil, am I correct in assuming that all this is done with a warm engine with the choke off?
Best Regards, Pat
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Joined: Jan 2002
Posts: 30,701 Likes: 141
ChatMaster - 25,000
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ChatMaster - 25,000
Joined: Jan 2002
Posts: 30,701 Likes: 141 |
It would best be done with a warm engine. Choke really has nothing to do with it but I would have it "off".
The main thing would be to do it at a slow idle so the throttle plate is closed and the vacuum advance port is not exposed to the vacuum. Also the advance weights are not in play.
Gene Schneider
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Joined: Jul 2009
Posts: 1,478
ChatMaster - 1,000
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ChatMaster - 1,000
Joined: Jul 2009
Posts: 1,478 |
I will add that be sure that the slide under the advance is well greased/oiled. This will allow the vacuum to advance freely on the Octane selector. Also you can check to make sure it is free by turning it with the engine off. It should have a spring action that snaps back when you release it. That tests the springs and throw out weights under the points in the dist. as well as free movement of vacuum advance. All of which is used by the engine to advance the spark automatically.
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