65 w/289 4bbl Weinan dual plane manifold/mild cam/Holley 600/Hooker headers/Pertronix ignition.

Can anyone tell me what the vacuum should be? Here is the issue: At an idle I'm pulling 12 inHg. The breaker plate in the distributor starts to move at 8 inHg. The timing is advancing before I even get my foot on the gas. When I rev it, it goes to about 25 inHg and hangs the breaker plate wide open and sometimes it sticks open and wont close causing all kinds of havoc. This issue cropped up after finding a huge vacuum leak in the carb spacer. I fixed all that and now I'm chasing this. The distributor was replaced with new at Restoration (finished the car this past fall) and there is less than 200 miles on the engine.

 

Your idle vacuum sounds low. Your vacuum advance sounds way off, and may not be connected properly, it should be connected to the timed port on the carb. You should have the distributor professionally timed. What type distributor is it?

 

I will recheck the idle vacuum again when I get home just to be sure. The advance is hooked to the carb. I'm a former mechanic, but this one kinda has me by the shorthairs. The distributor is a reman original single vacuum type.

 

Since you are a mechanic, you should understand what 2+2 is saying, that the vacuum advance should be hooked to a ported vacuum source and not a manifold vacuum source (carbs have both). With ported vacuum, you should not see any vacuum at idle, only after idle therefore your vacuum advance does not come in until after your engine rpms pass idle. When you "rev" the motor, your vacuum should go down, not up as the throttle plates are open and the air charge is moving freely through the carb into the cylinders. Vacuum is created when there is a restriction in air flow as in when your throttles are mostly closed during cruise speed/rpm. As for the dizzy advance sticking, there is something wrong with the dizzy as that should never happen.

 

First of all, if the breaker plate is hanging up in the distributor, this (real) problem is not a result of anything outside of the distributor. Sounds like the rebuild didn't take to me.

Secondly, if your cam is mild, the vac is way too low. If I were you I would start looking for vac leaks at the juncture of the head/manifold. Seeing as there was a leak in the carb spacer, I would not be the slightest surprised to find a manifold gasket leak.

 

I agree. I run a 280* cam and run 10-12" of idle vacuum at 900rpm. At idle, a janer street cam should be running more...15, 16, 17, 18

 

Depends on the type of cam, and the engine configuration, how much idle timing etc etc.

12" at idle with a "mild" cam is fine. It depends on what mild is too. My cam is mild by some people's standards, but a lot of people wouldn't think so because of the lift and idle vacuum it has.

 

Thanks guys for all the input. After checking everything, late last night I pulled the distributor out of the car and took it apart. I found there was only one spring on the fly weights (the light one) I replaced the springs and now it runs great. I bought it from a local parts place, and I will call them today to let them know the issue.

The cam is an Edelbrock, just a bit over stock.

Again, thanks guys for all the input. It never ceases to amaze me the knowledge on this Forum!!!!