Just a question, im running four 97's on my hemi with a vac adv MSD dist. Needing about 12 psi for it to work properly. Should i tap both of these ports and run a 2 into one deal or will one of these run enough throttle vacuum to work? Just wondering if anyone has run their vac adv off of 97's
Vacuum for vacuum advance should be sourced below the throttle blades, so that's not where you want to tap in. Actually, manifold vacuum is the best choice, so a bung matching the distributor connection installed on the manifold is all you need.
Put it in a Sun or Allen machine - respring & weight it for full centrifugal operation. You must remember that the vacuum signal volume is no longer enough to operate a vacuum advance dist. properly when divided among multi carbs. It'll run, but nowhere near as well as it will with a good full mechanical igniter.
Yea i was doin research on that between throttle vacuum and manifold vacuum. Some were saying manifold vac pulls 100% of the time but throttle pulls when you need advance. Tappin the manifold is easy. That was my initial plan to just match bung on advance canister on manifold. I guess i could test em once i get it running see whats best. Its a Ufab 4x2 manifold from geardrive. Thx for info just wondering how people handle this running multi two carb setups
Stromberg supply a base with the vacuum port fitted in the correct place. I used one on a triple carb set up and it worked well. The Stromberg part number is 9514-VP Heres the link http://www.stromberg-bulletin.com/stromberg-97-with-ported-vacuum/
no to manifold vac, its there all the time, there fore you'll have an extra 10 ish degrees of timing at all times (till you go WOT) you don't want vac advance all the time only when light throttle crusing. hence near the butterfly. Lots of rubbish on the net about it.
not WOT, but under a load the vacuum will drop and so will the advance, Use MANIFOLD vacuum for your distributor. He has 4 carburetors , so to even his carbs he will have to run 4 adapters. A LOT easier to just drill and tap the back of one of the manifold logs. Just remember, millions of cars built from 1957 to around 1980 used manifold vacuum to ADVANCE the distributor, Ford used venturi (above the throttle plates)vacuum to RETARD the advance.
""Ford used venturi (above the throttle plates)vacuum to RETARD the advance."" You have that back wards..Lot of Fords relied on vacuum to advance as they had no centrifical; i.e. 51 8ba, 65 comet 6cyl..{the same advance diaphram}
vacuum advance is for light throttle fuel economy, you can play around with all sorts of stuff but the engine will run best with mechanical advance set for the engine and fuel used then have vac advance for a bit of enconomy with the vac off the carb below the butterfly (and I doubt you'd need to do more than one carb). Not interested in vac retard or any odd pollution equipment weirdness......
who would put that thing on either a car that's the focus of this forum or any high performance engine? I don't know its exact use but looks like a pollution can to reduce NOX emissions by reducing advance? UTTER rubbish
Are the carbs opening in progression? If so, I would think one bung on the manifold would be enough. If progressive, by the time the other carbs kick in, the engine would have enough cent. advance and not be relying on the dist. for vac advance.
you have it sorted wrong if you rely on any sort of vac advance during acceleration, mechanical advance and total advance is all you should be using , vac is for fuel economy only. I think Ill go back to the shed, I have a block to clean. Lots more fun than hitting my head on a wall
As noted, vacuum advance is a fuel-economy device. Seeing how the OP is using four 2s on a log manifold, I doubt that it's functioning will make any difference....
Running four '94s in synch on the 324 Olds with mechanical (centrifugal) only. Runs great. Tried running with a vacuum advance (for improved fuel economy) but made the timing process a nightmare. Remember the mid '50s thru the '60s, several hi-po engines came factory equipped with mechanical-only equipped distributors.
My engine builder says vacuum advance IS NOT needed, even for my mild 327. I need to come up with a way to disable mine while retaining it for the stock look I want.
Vac advance should work and shouldn't make timing any more difficult (if the signal comes off the proper place) its an additional advance on top of your max advance. No you don't "need it" BigDogSS you engine builder is correct, its for fuel economy, wont make it run any harder, it wont hurt if set up correctly though
Very little. Connecting at the carb may introduce some restriction and limit how quickly the advance responds, but generally speaking, it's all the same. I personally prefer a manifold connection for no issues with advance response, plus you can hide the connection easier in most cases.
49 thru 53 flathead fords used metered carburetor vacuum as the sole means of advancing ign. Timing.....it is usually a mistake to make "always"or "never"statements , that said I would not use vacuum advance on a high performance engine....and BIG DOG all you need to do is push a piece of golf tee or nail or any reasonable press fit plug in the vacuum hose to disable your vacuum advance,( don't use a screw as vacuum could leak past the threads...
The Jalopy Journal
