I was reading the other thread in the race section on whether or not to use vacuum advance and this got me to thinking about dumping the vacuum advance on my 417 stroker.

Ever since I built this motor I have never gotten it to idle well without setting the idle at 950rpm (or higher). The reason I'm thinking about dumping it is that when the idle is set below 950 the engine has a slight pulsing idle to it (with the vacuum advance canister connected to the carb). I have read that this is due to an issue with the vacuum advance canister (amount the canister needs) and the engine vacuum.

My engine produces about 14in of vacuum but due to the cam it has a rough idle so I'm thinking this might be messing with the vacuum advance canister an hence producing the pulsing idle.

So my question is can I just unhook the vacuum advance on the distributor and plug the carb vacuum hose stub and just drive it that way (note: I don't want to modify the distributor)? The distributor was curved by FBO and this was assuming I had the vacuum canister attached, so I'm not sure if there are any consequences to unhooking the vacuum advance and driving it that way.

Also just for the record, I don't care about getting a little better gas mileage using vacuum advance so no need to bring that up.

Thanks

Vacuum advance is for part throttle driving to give more advance and better mpg. Full throttle(near zero vacuum) the canister does nothing.

You don't need to use it if you don't want. Total timing will not change during full throttle. Try tuning without it then try to add it later on. You can also adjust them to change the amount of vacuum is required before it starts adding timing. Just use an allen wrench in the small hole, sorry forgot the size.

With a bigger cam (granted your pulling a fair amount of vacuum) the power valve in the carb can really screw you over on tuning for a nice idle.

Depending on cam,950 rpm's at idle is about normal.

This ain't the slight lope of the cam but is it a "pulsing" like a quick/brief miss with a split second or second of time between them? First I'd find out if a 950 idle is normal for that cam (I'm assuming no) & if Don curved the dist for you to be on manifold (vac adv activated at idle) vacuum & I imagine at 950 RPM the vac adv will be activated even if on ported which ma or may not be what he curved it for especially if it was expected to idle slower. timing may be excessive (when you retard it does the "pulsing" stop?), rotor phasing may be off. A valve may be hanging up or be burnt. I dont think the vac adv is the cause unless the timing is excessive & if so the timing needs to be adjusted elsewhere & keep the vac adv especially since Don set it up that way. Need more info/do some checking. IF you do lose the vac adv yes you can just unplug it & cap the hose then recheck/reset the reluctor gap/check rotor phasing as vac adv changes both of those & reset your timing