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what effect would there be if the vacum advance playing up. i have just put weber 32/36 on car to try and improve economy and get more power but it has made very little diffrence and when i take main vacume line off manifold car revs up ????

I believe that that is because that vac line supplies vac to the dizzy and advances/retards the timing depending on engine/throttle load.
It could also be reving cos when you take the vac line off, that is letting more air past the carby and into the engine