Use or don't use vacuum advance on distributor???????????????????

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OwdKasd said:
I am running all MSD with no Vacuum advance on Billet distributer. My car Runs Great for me. I don't race it I just cruise around like an old lady but I have no problems whatsoever.
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I bet it does, but I wouldn't be surprised if you're leaving some gas mileage on the table.
 
So, the chevy boys can buy a vac can that will open with less vac.
What about us? any available?
I have the MP elect. conversion and have been running without vac adv.
My cam does`nt pull enough vac to even operate the can. I`ve tested.
 
mopar head said:
So, the chevy boys can buy a vac can that will open with less vac.
What about us? any available?
I have the MP elect. conversion and have been running without vac adv.
My cam does`nt pull enough vac to even operate the can. I`ve tested.
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Good question
 
Badsport said:
I bet it does, but I wouldn't be surprised if you're leaving some gas mileage on the table.
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I am sure you are right. I don't really drive far enough to ever get a fair MPG estimate but It sucks up fuel for sure.
 
OwdKasd said:
My car Runs Great for me.
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This is really what it's all about. The worlds full of individuals. Some owners don't know, some don't care, some are very happy as it is... All that's really important is the owner is satisfied. For me, that means running one.


The last time I checked one, which admittedl was years ago, the stock vacuum can started being affected at 7-8" of vaccum.
You can adjust it by sticking an 11/32 allen wrench down the vacuum nippled on the distributor can, but all you're doing is adjusting the amount of vacuum it takes to move it. Not the amount of degrees of advance.
Crane used to offer a performance curve kit for small blocks with a vacuum can that was better with lower vacuum levels. I bought the last 3 I saw on Ebay a few years ago but every once in a while once shows up.
The only difference between ported and manifold vacuum source is the advance at idle. Ported does not allow for the vacuum pod to affect initial timing. Manifold does. Otherwise - they do the same things, at the same times. The way it was taught to me this was to prevent the timing from bouncing around if the idle vacuum was unsteady. It had nothing to do with hydrocarbons or convertors because as I said, at the time they were added, nobody gave a rats *** about emissions - even in CA. Some manufacturers were wary of erratic idle, and some weren't. I think it was Ford that had both vacuum advance and retard in the same dashpot that was controlled by a temperature controlled vacuum switch and the throttle position.
 
It was Ford. I remember them well. Had a vacuum nipple in front of and behind the center of the vacuum diaphrgam.
 
moper---but all you're doing is adjusting the amount of vacuum it takes to move it. Not the amount of degrees of advance.


Maybe the OEM was this way but the MP conversion vac. can. adjustment just limits/increases the movement, not the amount of vacume it takes.
If this were the case we`d be golden with low vacume cam engines
Or am I wrong?
 
The advance can on my MP distributor can be adjusted to control when it is actuated. When I insert an allen wrench into the nipple, one full turn in either direction raises or lowers the point of actuation by approx. 1" of vacuum.

I'm not sure if it's the original can or one put on by Don at FBO. Doesn't really matter though because the MP instructions that come with it confirm that's what you're doing.
 
What I want to know is can you get the MP vacuum can by itself? I haven't been able to find one.
 
70Duster440 said:
The advance can on my MP distributor can be adjusted to control when it is actuated. When I insert an allen wrench into the nipple, one full turn in either direction raises or lowers the point of actuation by approx. 1" of vacuum.

I'm not sure if it's the original can or one put on by Don at FBO. Doesn't really matter though because the MP instructions that come with it confirm that's what you're doing.
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My instructions does`nt mention any reduction or increase of vacume by adjusting it.
What it does mention is [turn allen wrench (180 degrees) clockwise to reduce vacume advance by aproximately 2 to 3 degrees]. That`s advance, not Hg or " of vacume
 
mopar head said:
My instructions does`nt mention any reduction or increase of vacume by adjusting it.
What it does mention is [turn allen wrench (180 degrees) clockwise to reduce vacume advance by aproximately 2 to 3 degrees]. That`s advance, not Hg or " of vacume
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Right, it doesn't say that specifically - I'm deducing based on the section on tuning for maximum performance. It makes sense when you consider you're simply adjusting spring pressure against the diaphragm. I've confirmed this using a Mityvac.

With mine turned all the way in (fully clockwise), it takes a minimum of 10" of vacuum to start to actuate it. As I back it out, that number goes up. And 1 full turn seems to coincide with an inch of vacuum. Makes sense that I can add or subtract vacuum advance by adjusting spring pressure. Despite how the instructions are worded (with number of turns coinciding with an increase or reduction of timing degrees), I found that turning the adjustment clockwise reduces the amount of vacuum required to move it. Turning it counterclockwise increases the amount of vacuum required to move it (from 0*).
 
mopar head said:
So, the chevy boys can buy a vac can that will open with less vac.
What about us? any available?
I have the MP elect. conversion and have been running without vac adv.
My cam does`nt pull enough vac to even operate the can. I`ve tested.
Click to expand...

I came back to look as I thought this was asked. A LOT of Mopars came right from the factory with adjustable cans. If the can on your distributor has a "hex" on it where the vacuum nipple is, it is adjustable. They used those on everything from the slant 6 to the Hemi. I have a couple for a slant myself. Just some FYI.
 
mopar head said:
moper---but all you're doing is adjusting the amount of vacuum it takes to move it. Not the amount of degrees of advance.


Maybe the OEM was this way but the MP conversion vac. can. adjustment just limits/increases the movement, not the amount of vacume it takes.
If this were the case we`d be golden with low vacume cam engines
Or am I wrong?
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I've owned 2 Mopar conversion distributors (one old style and one of the newer ones with the Mallory type centrifugal advance mechanism) and both had the adjustable vac can and I tested both with a timing light and the adjustment did not affect how much timing it added, only affected the vacuum level in which it pulled in. Did you verify what yours does with a timing light?
 
moper said:
The vacuum advance, as noted, only affects part and light throttle driving. It is designed to maximize fuel mileage and keep plugs cleaner over their life time. Properly set, it does not negatively affect the engine at wide open throttle or idle, and in fact can add 10-30% more mpg depending on the setup and tune. It is a feelable difference when you're driving and I always run them when possible. There is a point where the vacuum characteristics of an engine package make it impossible to adjust the advance to work with it. That's usually with larger cams or engines that are overcammed. At that point, it's better to cap the line and run without it.
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Agreed
 
ev2 said:
can find the Echlin #VC-1810 advance can (about $10 at NAPA) or any can help
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Not sure what your asking but if you own a Chevy that's what you need. The article was written by a GM guy and he posted that part # for Chevy's. It won't work on a Mopar
 
Interesting reading and all the other comments. It makes sense to me....all the old 60's motors I worked on used manifold vaccum, and the ported vaccum came to be common as the emissions stuff came on.....along with temperature controlled ported vacuum and all that jazz!
 
Ok so what I need to do is tighten up the screw in the vacuum of the distributer to raise the level of vacuum it advances? I am using a manifold vacuum and if I hook up the vacuum advance it runs like complete dog **** because it is advancing the timing at idle.
 
Punisher66j said:
Ok so what I need to do is tighten up the screw in the vacuum of the distributer to raise the level of vacuum it advances? I am using a manifold vacuum and if I hook up the vacuum advance it runs like complete dog **** because it is advancing the timing at idle.
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So, reviving a thread from the dead. Answers first.
1. What's your combination?
2. What's your intended purpose?
 
Revhendo said:
So, reviving a thread from the dead. Answers first.
1. What's your combination?
2. What's your intended purpose?
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360 magnum engine with Holley carb and dual plane intake, stock electronic vacuum advance distributer, and everything else is stock. Every port of the carb has vacuum at idle so there is not ported vacuum only manifold vacuum. If I hook it up to the carb it will advance the distributer at idle so my vacuum advance won't work correctly. If I can't get the vacuum advance to work correctly I will go get a mechanical lean burn distributer and put it on the car. I can't afford a high dollar mechanical distributer right now.
 
Punisher66j said:
360 magnum engine with Holley carb and dual plane intake, stock electronic vacuum advance distributer, and everything else is stock. Every port of the carb has vacuum at idle so there is not ported vacuum only manifold vacuum. If I hook it up to the carb it will advance the distributer at idle so my vacuum advance won't work correctly. If I can't get the vacuum advance to work correctly I will go get a mechanical lean burn distributer and put it on the car. I can't afford a high dollar mechanical distributer right now.
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Car? Gears? Stock cam? Which model Holley?
You don't have a distributor problem, you have a vacuum problem. (For the most part).
 
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