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Is vacuum advance needed?

G'day all

Just a quickie, I was messing around with the old stato, and whacked on a carbi I rebuilt, when I was connecting it all up I realised that the distributor didnt have a vac advance module? it look to be after market electronic dizzy, has a red anodized control box wired to it HEI coil etc, but no vac advance.

Question is what difference will this make to the engine? would this have anything to do with the old girl running hot at idle for extended periods of time buy affecting timimg? Had a quick look over the out side and didnt see anywhere that looked like a spot to fit one (but didnt look that much so could be hard to see?)


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Vac advance

Doesn't really effect performance much IMHO but in a standard/mild performance street engine it will improve drivability and economy by having vacuum advance.

It comes down to how you use the car, if it was a daily driver you'd be wanting it, if it was a weekend cruiser it wouldn't be so important, and if it was a high performance/race engine you wouldn't have vac advance.

With the set up you have, depending on the mechanical advance curve and what's done to the engine you may need to give it a little more advance to compensate.


aka hq308belmont

My Shed

vacuum advance

Hi All

vacuum advance is need to boost timing on load, also it allows a more relaxed initial timing for times like idling at lights and starting up, otherwise you would be setting to say 15deg and suffering hard cranking all the time

also your heating at idle, check the usually suspect, timing , waterpump, radiator, fan but since you have done a carby swap check the idle mixture - i am betting its lean, my 253 used to creap up to red hot in 5-10 mins when siting at lights etc , it was way lean at idle


Vac advance

Not sure what you mean by "on load" but it should be clarified that vacuum advance only works under light load / throttle conditions when manifold vacuum is high. Vacuum advance has little or no effect under high load / full throttle conditions as there is little or no manifold vacuum.


aka hq308belmont

My Shed

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