Do you guys run a vacuum advance?

[Back N Black]

Just looking for opinions, advantages/disadvantages. I don't run a Vacuum advance and base timing is set at 22 degrees, car runs great (comp cam XE 274). I was thinking of running the advance and change the timing just to compare the two.

[c00nhunterjoe]

I do not run it on any of my mopars. I do run it on my wifes 72 nova. The advance curve on each of our 4 cars is different. Your results will be the same- different. And that is ok.

[John_Kunkel]

Q) Vacuum advance, yes-no?

Q) Plugged into timed port or manifold vacuum?

Always debated. Whatever works best for you.

[A383Wing]

all of my cars are set the way they left from the factory....vacuum advance connected, and plugged into ported vacuum at the carb

Bryan

[cdr]

An adjustable vacuum advance YES YES YES, best thing since sliced bread 

[Kern Dog]

I do. Static timing is at 17 degrees, with 14/15 degrees of mechanical advance for a total around 31/32.
My car is a 440 based 493 with 10.07 compression, the '528 MP cam with 1.6 rocker arms, 2" headers, 850 Demon 4 barrel.

[c00nhunterjoe]

440 based all aluminum 572. 14:1, indy 572 heads, solid roller, dominator. Runs 36° locked

426 max wedge. All steel, stock heads, stock cross ram. 12.5:1, .750/325 solid roller, runs 1 blue spring and black bushing on msd distributor, total at 40, 1 spring allows easy crank hot but under full advance off idle.

440 iron block alum indy 440-1 heads, 11:1, same cam as in 426 max wedge, 36 locked out.

72 350. Stock  low comp engine with holley street dominator and 650 vs holley. Hei distributor with vac adv on ported. 16/36 + vac.

Every combo is different

[Canadian1968]

I run the xe274 as well.  18* base no advance .

[TexasStroker]

Nope.

[XH29N0G]

I'm using mechanical advance

[cdr]

Once you run VAC,,,You'll NEVER go back LOL,,, TRUTH, it helps the engine run cooler, quiets down the exhaust tone, better fuel mileage, just a more efficient running engine   

[myk]

I am an advocate of vacuum advance, but I've been having trouble with mine so I disconnected it for now.  While hooked up it did help with part-throttle drive-ability and cooling...

[strokie451]

Once you run VAC,,,You'll NEVER go back LOL,,, TRUTH, it helps the engine run cooler, quiets down the exhaust tone, better fuel mileage, just a more efficient running engine    

I use manifold vacuum...
Fit helps the engine run cooler, quiets down the exhaust tone, better fuel mileage, just a more efficient running engine  

[flyinlow]

If your Charger is a race car or you only drive it to back it out of the trailer to drive it to the show parking spot don't worry about vacuum advance. If you drive it like a real car  vacuum advance will probably make it drive better. After setting up the base/ centrifugal timing I found I had to limit the amount of vacuum advance to about 8*.

Chrysler used it with ported vacuum.  If you engine will run well with manifold vacuum, great.

I use it on both Chargers. When I switched to EFI on one I let the ECU run the timing, I programed the ECU to simulate vacuum advance.

[Paul G]

 

[c00nhunterjoe]

If your Charger is a race car or you only drive it to back it out of the trailer to drive it to the show parking spot don't worry about vacuum advance. If you drive it like a real car  vacuum advance will probably make it drive better. After setting up the base/ centrifugal timing I found I had to limit the amount of vacuum advance to about 8*.

Chrysler used it with ported vacuum.  If you engine will run well with manifold vacuum, great.

I use it on both Chargers. When I switched to EFI on one I let the ECU run the timing, I programed the ECU to simulate vacuum advance.

Ive got 3 engines and 2 cars that you would consider race cars, neither of which run vacuum advance. They are not trailer queens and get more miles per year then many of the stock cars on this forum. Can you back up your claim with evidence?

[Paul G]

This article is written by Jeff Smith. I think we all know who he is. There are more articles and information on vacuum advance if you google it. I learned a lot about VA, and spent some time getting it to work correctly on my modified engines.

In short, a race engine doesnt need vacuum advance. There is no point. A race engine runs from idle to full throttle, nothing in between. A street engine spends most all of it's time between idle and full throttle. Thats when vacuum advance will add timing during lean fuel mixture conditions to give extra time to the flame front to fully burn and have the most bang about 12° after TDC, right where you want it. properly tuned vacuum advance can improve economy, help the engine run cooler, and increase driveabilty. Read the entire article.

https://www.onallcylinders.com/2014/09/05/ask-away-jeff-smith-basic-guide-ignition-advance/

[c00nhunterjoe]

When alot of your modified street engines are running 28 degrees of initial vs the stock 8-10.... it becomes a moot point. As stated above where the vaccum was limited to 8 degrees, 8 over what? Stock 8? So 16-20 with vaccum advance when you can start with your base and set your mechanical curve to get peak power. Thats peak power at all rpm ranges, not just 7,000 rpm. Ive yet to see a dyno sheet on here that only concerned itself with high rpm numbers. The power curve usually starts at 3000 and goes up from there. Vacuum advance was designed to provide more timing BEFORE the distributor reaches full advance. When we start adding cams intakes and headers, we drastically shorten the advance curve needs and vacuum advance becomes pointless and in many cases it hurts causing surges and pinging. If you can make it work on your modified engine and you feel it helps- great, but it is not required on a modified street engine.

[Paul G]

Your not wrong. Thats why VA has to be limited. I run a base of 18°, another 18° with mechanical advance all in by 2500 RPM. VA adds another 10° to 12°. Adding VA brings the total to 46°, but only at light throttle cruising conditions. Gas mileage sucks with VA or without, 12 MPG or 13 MPG, not much difference. I use VA try to keep the engine cooler. In theory, based on many articles I have read, it should help cool the engine too. Much needed on a 45 year old street car with a cam and trying to run A/C on a 110° day.

[c00nhunterjoe]

Your not wrong. Thats why VA has to be limited. I run a base of 18°, another 18° with mechanical advance all in by 2500 RPM. VA adds another 10° to 12°. Adding VA brings the total to 46°, but only at light throttle cruising conditions. Gas mileage sucks with VA or without, 12 MPG or 13 MPG, not much difference. I use VA try to keep the engine cooler. In theory, based on many articles I have read, it should help cool the engine too. Much needed on a 45 year old street car with a cam and trying to run A/C on a 110° day.

Agreed, fair enough.

[metallicareload99]

Once you run VAC,,,You'll NEVER go back LOL,,, TRUTH, it helps the engine run cooler, quiets down the exhaust tone, better fuel mileage, just a more efficient running engine   

Might as well have that combustion start sooner and help push on the piston rather than heating up your cylinder walls and exhaust manifolds

[tan top]

 Yes with current set up