OK .....I don't know!
The car has a 327 with dual points in the distributor. The distributor does not have a vacuum advance.
I'm running 3 deuces. Would it be easier on the engine if I got a distributor with a vacuum advance and ran a vac line to the center carb?

OR.....can I just put in a Pertronix kit and replace the points and not buy the new distributor with vac advance?

THANKS to all for the help.

All depends on how the mechanical advance is set up......

Thats why they degree distributers........for a set total advance at a certain RPM....then at idle it drops to where you want it for easy starting etc.

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I'm running a mechanical dizzy, Mallory Unilite and have no problems with it. My low end is hampered by a 2.20 first gear in an M21, and 3:08 rears. Was trying to run with 12* initial, but the curve was all wrong, getting too much advance. Ended up running 20* initial, all in 38* at 3000rpm, no problem starting and no detonation. Still have a little bit to do on the curve, coming in a little too fast. I am adding a MSD 6al to boost the spark, getting some loading from around town cruising. There are lots of spring and tuning kits available and plenty of information to get your curve right. You'll get better gas mileage, and some say runs cooler with vacuum advance. Your choice!

vacuum advance is a wonderful thing for MPG and throttle response if set up right. Race engines that don't worry about wide RPM ranges and off-idle performance often run without vacuum advance. Boats run without it because the loads are so high for a given RPM that its pointless.

but I think you'll prefer a car with vacuum unless its a strip car.

I stopped using vac advance on my street toy a couple of years ago and it works better without it.It used to ping and had a slight hesitation at part throttle tip in with the vacuum hooked up,now thats gone.I havent noticed any difference in gas mileage or spark plug life.Do what works best for the situation is my advice.

I haven't used the vacuum advance on any of my cars since the 70s.

We have always used the Maroso dist. with no vacume advance and have set them up with the lite springs for the street engines we build and so far no complaints on milage or performance.

No vacume advance for me either smc 400, runs better without it.

Yes, it's dumb to not run vacuum advance on a street car.

We build a lot of 11:01 stree engines 355 and 383's and running vacume advance on these engines does not work and we have some mild 331's with Vortec heads and no vacume advance and these engines runn fine and the customers are very happy with the performance in there street cars. Short curve lite springs has always worked at our shop.

At our shop we don't think its very dumb HMMMM

Vacuum advance may work better on factory low performance vehicles that need help with controlling emissions but from the responses on this thread so far it would certainly seem to indicate that high compression performance street/strip engines that are on the "edge" of detonation definitely work better without vacuum advance.No one can say that vacuum advance is the absolute correct answer for every application.

In your first case I suspect it's due to detonation. Doesn't make sense to detune an ignition system to compensate for too much compression. That is my sense in that situation.

In the second situation it may run fine without but it will run better overall in a street situation with a vacuum advance system.

I as well do a lot of tuning on customer vechicles including full retrofit custom EFI. I can very easily demonstrate to anyone the differences in optimizing ignition curves and how it affects overall driveablilty in real time.

For the most part i agree with Rick,,,Almost every street engine will work better with a vacuum advance hooked up,,,,, If it's set-up correct..

For years i used to run with-out the vaccum advance and once i figured the correcy way to get them to work it always helped the engine at idle and part throttle... Of coarse we all know there are combo's that just will not tolerate it..

One of my personal street car run with a locked distributor, no vacuum no mechanical... But it's not the normal engine that most guys would run on the street...The other car has mechanical and vacuum hooked up... It's driven by the combo....


Keith

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Performance Engines
The crash was easy: rehab is killing me-"John Force"

The key to either system is setting up the curve, which most people don't understand, or take the time to do.

As jsdailey says the advance curve must be set correctly.I now use an MSD # 8365 distributor that is adjustable several different ways.You want to have your total timing in by a certain RPM,usually around 3000,let your initial fall where it may,then play with bushings or springs until you get your desired performance level.A correctly tuned performance ignition does not necessarily need vacuum advance.