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Vacuum Advance Keeps Breaking


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A little while ago I was fighting with trying to tune my carb. when I noticed that the vacuum advance did not hold air, causing a vacuum leak and no advance. I thought that that was kind of weird (its only a couple of years old) but I went ahead and replaced it. Now its a week later and the same thing happened! What would cause the diaphragm to keep ripping?

 

The setup I have is a 4.3L V6 (practically the same thing as a small block Chevy) It has a Demon 525cfm carb. and a Mallory Uni-lite distributor.

 

I checked to make sure that the vacuum was connected to the correct port and it was. However, the line (just some clear plastic tubing that I had lying around at the time of the build) was blackened and hard on the end that is connected to the carb. I'm not sure if that is a sign of anything.

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Yes it can, if the vacuum hose turned black which was clear before and it is hard then you are getting gasoline in the line which is probably causing your vacuum advance to go bad. I would pull both float bowls of and the needle seats out and clean good. Sounds like some trash in the carb getting caught in the needle seat keeping it open and flooding out your carb.

 

John

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