Technical Multiple carburetors and vacuum advance

Hey fellas... Getting ready to finish assembling my engine (292 Y-Block in a '54 Merc) and I'm running 3 Holley 94's on an Edelbrock 573 intake. I planned on using my Mallory Rev-Pol (centrifugal advance only), but it's old, needs to be put on a machine, and needs condensers which are hard to come by in good shape. Anyway, if I go with a vacuum advance distributor, I assume I'd be using manifold vacuum? Obviously I wouldnt be using the vacuum signal from the 94's advance port. I've always run mechanical advance distributors on multi carb set ups.

Thanks!

 

Send the distributor to bubba,he'll run it,put condensers on it, even pertronics if you want it,and you'll be good to go! A little money now will save a bunch of dicking around later. Just allow lots of time.

 

Yes I would assume manifold vacuum just like a single carb set up, I don't think multiple carbs would change that?

 

I run the vacuum line off the rear carb on my dual quad 292 y-block which is the lead carb. It's the stock port normally used (WCFB). I use a 57-up vacuum advance dist with a Pertronics II with the ballast resister. I have always used a vacuum advance with multicarb unit. Good luck.

 

I'm pretty sure that Bubba may advise you to run a non vacuum distributor, he did for me with my Y block and tri power. I sent him an old rare Holley distributor that was originally a vacuum unit and he rebuilt and converted it to non vacuum with the proper curve and a Pertronix system.
Depending on the cam you use, you may want to do the same.
My engine builder Tim McMaster advised the same thing.

 

Non-vacuum advance on the street, huh? Seems like strange advice. What's the reasoning?

 

I think that the Y Blocks like it better when you run a bit of cam. Seems to be the way a few of the guys go.

 

'... like it better...'

Seems like a rather vague reason. A properly set up vacuum advance will have zero effect on timing at WOT and under heavy acceleration, offers much improved fuel economy and will make the engine burn cleaner.

 

Yes probably is vague as I really don't have a definitive answer. All I know is when I sent my Y Block distributor to Jim at Bubbas he asked my engine specs and carbs, I left it up to him to build it and set it up.

Then when I picked up my engine I was asked about my distributor by Tim and told that it was best to run a mechanical advance with 30 degrees at a certain RPM. Exactly how Jim had set up my distributor.

So, Bubbas and then Tim McMaster said the same thing.

 

I run mechanical on one or several carbs pretty much all the time. I have only done it for 40 years or so though and my engines may not run worth a flip and I just wouldn't know it.

I have heard compelling arguments for both distributers and can't really find fault in either. I even know a guy that is only pulling about 10" at idle who runs a vacuum advance and he likes it, off idle his vacuum comes up enough to make it work I guess.

 

There is no good reason not to run vacuum advance on a street engine, no matter what anyone says.