What i have is a 1972 dart swinger with a .030 over, cast crank 440. It has the TRW 2355 six pack pistons with compression height of 2.062. Open chamber stock 452 heads. Compression ratio is right at 9.4:1. It has the mopar performance 284/484 cam installed 4 degrees advanced. Stock intake and a built thermoquad. 1 7/8 hooker fenderwell headers. I have the distributor dialed in at 18 degrees initial and 32 total. I have not been running the vacuum advance..but should i be? I didnt think cammed up engines were supposed to run the vacuum advance but been hearing conflicting things about it..

Yes, no reason not to

I would but you could experiment with maxing things out with and without it & see how it plays out. Right now I would tune what you have as 18/32 sounds a bit low (but pinging or a time slip is the judge) plus your spring combo you have?. EDIT & with it you might experiment with ported and manifold

seems like when I tried it before it would buck and jump at a light cruise..explain more how to use this..It only comes into play from right after start up until WOT correct, then it drops to the 32 total mechanical I have? Where should I hook the vacuum to?

you first need to get your advance curve perfected for your combination. initial timing and total mechanical timing. if the setup you have runs the best at 32*, then you can usually add around 10* or so of vacuum advance at cruise, which will give you better driveability, as well as better gas mileage.
rick eherenburg [member here] did a vacuum advance tuning article in mopar action magazine some time ago, explaining all the benefits of using it. however, it does take a little effort to find out the best combination for your application.
you mentioned a bucking condition when you hooked yours up. have you done anything inside your distributor, such as altering the advance slots or changing the springs, or is it just a stock setup ?
you can hook up the vacuum can to ported vacuum at the carb, or manifold vacuum [full time], and the can has a 3/32 allen screw accessible through the hose nipple that can slow down the diaphragm apply.
i know i have that article somewhere, but you may want to google "vacuum tuning" to see if you can find it.
also, FBO ignition has a plate you can plop in a stock distributor that allows you to set more initial, then the plate limits your mechanical total. that allows you then to tune your vacuum advance to your liking without sacrificing your initial timing.
hope this helps some.

I would set the initial with the "vac gauge method" then with that # in hand set the total (initial+slots) to 36 by welding up/shortening the slots (I just found out there is an issue with the FBO plate) then mix/match springs so you are just under the pinging point at WOT up thru the gears on your hottest/driest (most likely to ping) day then plug in the can to ported (no vac to can at idle) & work with it so that you are just under the pinging point in everyday driving under varying load/RPM conditions (3/32 allen wrench & there are can with different in hg starting points. this may take alot of experimentation & for a radical build you may very well want to omit the can & there are manifold afficionados such as Don at FBO who swear by it. Bottom line NO pinging ever tho you want to stay fairly close to that line but never over it & peoples' hearing varies so give it a cushion & gas is crap. Do check rotor phasing for the bucking/jumping at light cruise & I am assuming you ain't too lean/nor too much timing.

I already have it dialed in with springs and the slot limited..so where should i hook the vacuum up to, the intake or carb? Also, when adjusting the can through the nipple, what exactly does that do? Does it limit the amount of cruising advance or what? I just really dont understand how the vacuum advance works or comes into play..I understand the initial and total and like i said, i already dialed those in a long time ago and it works well, but want to try the vacuum advance too!

also, IF i am remembering correctly, waaaay back when this 440 was totally stock, meaning a low compression smog 440, it still did the bucking under light cruise with the vacuum hooked up. After i built the engine with more compression and the cam and all, i didnt use the vacuum..I did hook it up one day for the heck of it and i THINK it still did the bucking..?

The vacuum advance should go to ported vacuum on the carburetor. If it surges with the advance hooked up adjusting the advance with an allen wrench to raise the amount of vacuum necessary to move the advance should help. You might need a different advance unit with fewer degrees of advance if the allen wrench adjustment fails to cure the surge.

This is the original distributor to this engine. i have the advance slot filled in some to give it 32 total because it pings with any more than that. So can the vacuum take it even farther than the limited 32 total i have? Just not sure how the vacuum part works..

As is right now, pings at part throttle or wide open throttle? Or both.

I just went through this same issue on with my Roadrunner.

Is your vacuum canister adjustable? If so, take out a turn of preload and see if it helps. Sounds like the vacuum advance is advancing into detonation.

No, if i go beyond about 34 total, it will ping at W.O.T.. The issue i had with the vacuum advance was the bucking under a light cruise..The vacuum advance shouldnt bother the WOT should it being it drops off when you stab the throttle and it falls back on the total mechanical i have set, correct?

I actually argued with Eherenberg about this topic before. Not ALL cars can use a vacuum advance and they don't all respond well to the advance at part throttle. Most cars with more cam than stock will surge at highway speeds with vacuum hooked up.
I just prefer to set the base and total timing and lock it in there. I have a long duration high lift solid cam and my engine runs best with 23* base and 34* total with it all in by 2000 RPM.

Gus

The vacuum advance will not add any advance at WOT due to no vacuum at WOT, it will still be 32 degrees at WOT. Your engine can take and needs more than 32 degrees at light throttle cruize to help burn the leaner fuel mixture and smaller fuel charge.

Can you remove the cap & check rotor phasing? eyeball would show it if it is way off or a vacuum pump. You are looking for how far the rotor is away (around the circumference) from the dist cap terminal from zero vacuum to full vacuum AND the rotor tip to cap terminal "radial" distance is part of this as it is the TOTAL air gap cuz if the circumferential+radial gap total distance is greater than what the available voltage will jump then it will misfire. OR note the RPM it bucks/surges at under "light cruise" WITH the can then in your driveway with a dialback see how much advance you have at that RPM then plug the can & adv the dist so you have that same amt of advance at the same RPM then take it out & at "light cruise" at the same RPM without the can & does it buck & surge?

The vacuum advance is for fuel economy. It comes into play when you are cruising with the throttle plates mostly closed and are generating high vacuum.

If you want to set it up, hook up a temporary vacuum gauge to the switched (above the throttle plates) port on the carb.
Go for a ride. Find a flat stretch of road where you can cruise along in high gear without using much throttle. Take note of this reading.
Use a vacuum pump and gauge to set the vacuum advance for full stroke at the cruising vacuum noted above.

Example:

At cruising speed, you read 16" of vacuum.
Remove the vacuum advance unit, pump it up until the arm is fully retracted, note this reading.
Adjust the allen screw so that full arm retraction equals 16" of vacuum.
Reinstall and test drive again to ensure there is no pinging at cruising speed.

You might go with a stiffer spring to slow the curve & see if that elims the pinging. Work with either spring cuz other than the OE heavy one with the elongated loop on one end (which I assume is tossed), any spring combo advances the timing in a linear rate no matter what combo of spring tensions you have. (& note what RPM it maxes out at just for reference).

it will take more than one try to get it dialed to perfection, so don't get discouraged. every engine is different. some like more timing in quicker, while some like less timing in slower. or vice-versa, even a combination of some in quick/slow, then the rest in quick/slow at xxxx RPM.
get a notebook and keep notations [so you don't get lost] of your changes and the engines reactions, then try something else. strictly trial and error till you find the optimum.

^^^ agreed, it's gonna take some doing.