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Vacuum advance distribution question

Posted By: bobs69

Vacuum advance distribution question - 03/12/23 10:57 PM

If my vacuum advance is bad can I unplug it and set the timing at 32-34 and drive it? Just a street car that gets driven on good weather days.
Posted By: Ramman

Re: Vacuum advance distribution question - 03/12/23 11:02 PM

Sure can. Plug the vacuum line. All you'll lose it a little throttle crispness and fuel mileage.
Posted By: bobs69

Re: Vacuum advance distribution question - 03/12/23 11:11 PM

Thank you. Most of my time was in a drag car. Wasn’t sure about a street driver
Posted By: moparx

Re: Vacuum advance distribution question - 03/12/23 11:36 PM

yes, no problem.
however, if it's possible, i would try to get a good [new perhaps ?] can and tune both circuits to get the best of both worlds.
especially if you do any street driving at all.
just my opinion. your mileage will vary.
beer
Posted By: PhillyRag

Re: Vacuum advance distribution question - 03/13/23 03:32 AM

Most adverse condition will be at a steady, light throttle, highway condition
Mileage will suffer I believe.
Posted By: Cab_Burge

Re: Vacuum advance distribution question - 03/13/23 04:54 AM

Most of my hot street cars (500+ HP) have MSD or Mopar distributors with no vacuum advance on them or I disconnect them for the best W.O.T. performance up I'm not worried about the gas mileage whistling devil
Posted By: DaveRS23

Re: Vacuum advance distribution question - 03/13/23 01:31 PM

Beside some gains in economy, proper vacuum advance allows the engine to run cleaner. For the same light load cruising, it takes more fuel to do without that advance. That leads to additional deposits in the combustion chamber and on the cylinder walls.
Posted By: topside

Re: Vacuum advance distribution question - 03/13/23 03:20 PM

Street engines definitely run cleaner with vac advance.
I've proven that to myself, with 540 - 600 HP street Mopars.
No matter the amount of max power, most street driving is at a fraction of WOT.
The chambers on our older engines aren't as efficient as the newer high-swirl designs that require less timing.
Posted By: TJP

Re: Vacuum advance distribution question - 03/13/23 03:48 PM

Originally Posted by bobs69
If my vacuum advance is bad can I unplug it and set the timing at 32-34 and drive it? Just a street car that gets driven on good weather days.

There is a lot more to the subject than is being discussed. The first answer is correct, BUT as mentioned there may be a loss of gas mileage and low end throttle response.
You didn't mention the car, combination or how you "DRIVE" it on good weather days.
Getting the optimum performance requires a combination of initial timing, mechanical advance (how much, where it comes it and how fast), vacuum advance and jetting. The first three variables can have a substantial impact on performance and MPG. I have seen many cars with TOO MUCH vacuum advance which can lead to misfiring and a loss of MPG.
You could try bumping the initial a couple of degrees to give you a higher total as long as you're not introducing detonation or hard starting when hot.
now you have way more information than you asked for grin beer
Posted By: Sniper

Re: Vacuum advance distribution question - 03/14/23 08:54 PM

Originally Posted by Cab_Burge
Most of my hot street cars (500+ HP) have MSD or Mopar distributors with no vacuum advance on them or I disconnect them for the best W.O.T. performance up I'm not worried about the gas mileage whistling devil


Are we in the race forum?

I didn't think so. Try some useful and relevant information, please.
Posted By: TJP

Re: Vacuum advance distribution question - 03/15/23 01:20 AM

Originally Posted by Sniper
Originally Posted by Cab_Burge
Most of my hot street cars (500+ HP) have MSD or Mopar distributors with no vacuum advance on them or I disconnect them for the best W.O.T. performance up I'm not worried about the gas mileage whistling devil


Are we in the race forum?

I didn't think so. Try some useful and relevant information, please.

Cab has contributed far more than you could hope to. Your entitled to your opinion but your comment has nothing to do with being helpful to the OP, but rather yourself. Why do you have to come across so inflammatory? SOme of your post IMO are helpful while others are quite the opposite. please think before you post beer
Posted By: Sniper

Re: Vacuum advance distribution question - 03/15/23 01:49 AM

Originally Posted by TJP
Originally Posted by Sniper
Originally Posted by Cab_Burge
Most of my hot street cars (500+ HP) have MSD or Mopar distributors with no vacuum advance on them or I disconnect them for the best W.O.T. performance up I'm not worried about the gas mileage whistling devil


Are we in the race forum?

I didn't think so. Try some useful and relevant information, please.

Cab has contributed far more than you could hope to. Your entitled to your opinion but your comment has nothing to do with being helpful to the OP, but rather yourself. Why do you have to come across so inflammatory? SOme of your post IMO are helpful while others are quite the opposite. please think before you post beer


Cab's comment has nothing to do with being helpful to the OP.
Posted By: topside

Re: Vacuum advance distribution question - 03/15/23 02:11 AM

Seems to me Cab was saying he runs his hot street stuff without vacuum advance, and has found no issues with his engines.
That would be germane to the topic.
I think vacuum advance is a proven asset on the street - if properly tuned - but it's likely Cab doesn't drive the cars he's referencing on the street all that much.
He can expand on that if he wants to.
Posted By: Cab_Burge

Re: Vacuum advance distribution question - 03/15/23 02:50 AM

My daily street driver is a 2006 Ram 3500 4X4 single wheel C.T.D. or my wife 1996 Camry if she is going with me so she can get in and out better than with the truck.
I drove my old pump gas street Duster in the spring, summer and fall with no vacuum advance on it ever when I wanted to upset the local street enthusiast, especially the Mustang and Camera guys devil hammer grin
I'm not sure how that combination would run against the new Red Eye and other new hopped up supercharged factory cars work shruggy
That car ran a best of 9.993 at 134.7 MPH in the work 1/4 mile corked up with the air cleaner on with me in the car weighing 3450 Lbs. on Oregon 91 octane pump swill shruggy
Traction is king at that level, that car would hook up in a mud puddle in a rain storm whistling grin
Posted By: PhillyRag

Re: Vacuum advance distribution question - 03/15/23 06:12 AM

Originally Posted by bobs69
If my vacuum advance is bad can I unplug it and set the timing at 32-34 and drive it? Just a street car that gets driven on good weather days.


So basically yes you can. Can be unplugged for racing purposes, or performance street use. But for best "overall" street use, install it.
Posted By: Mebsuta

Re: Vacuum advance distribution question - 03/20/23 11:36 AM

Mine quit working several years ago. I couldn't find a replacement, so I bought another distributor for the vacuum advance canister, and that one was bad too. I gave up and do without. A 383 RR with a 3.91 gets horrible gas mileage rumbling around the city no matter what. I'm always speeding up, slowing down or idling at lights anyway, so whatever.
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