School me on vacume advance..........

I've been reading off and on for 2 days. So much info..... Most of it conflicting. I know how and why we use va***e advance. And of course a street engine will run better with it hooked up. My question is will it damage the motor with out it? IE: over heating, fouled / burned plugs?
I'm talking a bone stock sbc, street driven, a lot.
So why even think about disconecting the advance? I want to go to a multi carb set up and the HEI will not fit. Yes I know there are small body HEI units available as well as original looking points style with magnetic internals. But I'm looking at getting a magneto style distributor from Procomp and it has no advance.
Please no flaming me for running an HEI or a "fake" magneto. My names on the ***le.
I'm hoping to hear from some of you that have been running without vac adv for some time and get some real world feedback.
Thanks in advance guys!!!

 

mechanical advance is whats in the procomp stuff.

If its not vacuum, its mechanical.




.

 

I didn't know that. So it's locked in? Wonder what the specs are? Anybody?

 

Its not locked, it self adjust with weights using centrifugal force.. You can adjust by using heaver, lighter weights.

 

So it's adjusting according to rpm instead of va***e? Ok, same question. Who's doing it a a steet driven car and with what results?

 

Most of the guys using mechanical are running a big cam and an automatic trans. Vacuum advance just wont deliver with a big cam. Not enough vacuum to pull the advance.

 

I understand that. And I understand it will affect economy, reliability in a stocker on the street. But will it harm it.

 

no harm at all.

 

No problem without vac advance, but you need an advance curve thats faster.Easy to check with a dial back timing light.Depends on the specifics of your motor.

 

V-A-C-U-U-M. Part of the schooling.

 

The engine does not run better W or WO a vacuum advance if each way is set up correctly. It gets better mileage when cruising and runs cooler in traffic with a properly working vacuum advance. It's a street system but not a performance increase. Most race cars don't run one but race cars are not concerned about gas mileage at 65 MPH for long periods of time. Most street cars from the 60s have them. A vacuum advance is not a detriment to performance....and they should be connected to full manifold vacuum so that you get the maximum advance at idle for a cooler running engine in heavy traffic.

 

Haven't run one in my street g***er since I built it. Cruises and drives great. Never gets over 195, even in the summer, and gets 16mpg with 3.73 gears cruising on the highway. 6,000 street miles this year.

 

See post #2 in the following link. C9 (RIP) makes great sense out of timing and vacuum advance.

http://www.jalopyjournal.com/forum/showthread.php?t=43508

 

Thanks for the feedback. 1971bb427, thanks for the real world experience. I drive a little more than that but not much and our climates are about the same. I was some what concerned about over heating.
Sounds like mechanical advance for my application and a properly set up advance curve.
Thanks!!!

 

How many of you use a vacuum gauge to set the carbs and timing connected right off the manifold?

I have used this method for years and it seems to work like a charm every time.

What are pros and cons of both methods.

Jimbo

 

Was helping a neighbor who was trying to get his stock 66 Mustang 289 and C4 to leave the stoplight without stumbling. He had rebuilt the carb which was no help. I asked if he checked the vacuum advance and he hadn't. ****ed on the advance line and it was like a straw. Ruptured diaphragm. He has it disconnected and plugged right now and no more stumbling on take-off. He basically had a vacuum leak at idle.

 

all distributors ave mechanical advance, then some use vacuum on top of that....
mechancial is changed by changing springs, this changes the rate of advacne, sooner, slower etc.

weights and advacne bushings, change the amount of advance 20-22-24 etc


vac*** is used on top of that for part throttle economy, demands for the engine etc.
vacuum is usually around 10-18 inches


guys have run with and without...I am actually going to an accel dual point without...

 

All great info. Going to be interesting how it runs when I'm all done.

 

Its good to understand why you need advance at all.
The reason for it is to get the burn of the fuel and air mixture to have it burnt fully at TDC.

There is no explosion, just a really fast burn, and the time to burn is approximately the same.

So when the rev go up you need to start earlier.
Thats the reason for mechanical advance.

But when you travel att constant speed's the you can lean out the mixture, to save fuel.
And here is where the va*** comes in. Leaner mix burns slower, and need to get started earlier.

So Va*** is for milage.

Saying this it was so that Ford 8Ba flathead used va*** to advance, when the rpm got up.
And will work backwards if connected to manifold va*** .But that's Another story.