Vacuum advance position
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 2,158
Likes: 9
From: N.E. WA
Vacuum advance position
If the distributor is installed correctly in a SBC, and I have about 12 degrees of advance, where should the vacuum canister point? (approximately) Should it point forward or be behind the carb? Mine is behind the carb, am I one tooth off? TIA,
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
It makes no difference where the advance unit is pointed as long as you can set the proper timing. Besides rotating the distributor body, wires can be moved. You can put the advance unit just about anywhere,
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Safety Car
Joined: Feb 1999
Posts: 3,631
Likes: 14
From: Fountain Hills AZ
If by "correctly" you mean as origninal, at 12º BTDC the port on the canister would be pointing towards the right (passenger) side of the carb. If a vacuum advance distributor is installed in another postion (i.e., a tooth or more off) you might not be able to set timing where you want it because the canister hits something (usually an intake runner on the left or the coil on the right).
Safety Car
Joined: Jun 2004
Posts: 4,652
Likes: 80
From: Lakeland Florida
What year car do you have, and is it a mechanical tach drive?
The usual position would have the vac advance can pointing toward the right front of the engine.
If it is a tach drive ( and I am referring to the C3 68-73 years ) then there was a Chevrolet bulletin about the position of the distributor and the tension on the tach cable. The bulletin explained that to remove the tension on the cable, and cause premature drive gear failure to have the position of the dist.rotated clockwise so that the cable would not bind. You need to verify that the relationship of the rotor to the correct plug and firing order is not changed.
kdf
The usual position would have the vac advance can pointing toward the right front of the engine.
If it is a tach drive ( and I am referring to the C3 68-73 years ) then there was a Chevrolet bulletin about the position of the distributor and the tension on the tach cable. The bulletin explained that to remove the tension on the cable, and cause premature drive gear failure to have the position of the dist.rotated clockwise so that the cable would not bind. You need to verify that the relationship of the rotor to the correct plug and firing order is not changed.
kdf
