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Re: Is Vaccum Advance Really Such a Bad Idea [Re: fatman] #2888130
02/14/21 01:39 PM
02/14/21 01:39 PM
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jbc426 Offline
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I ran my RB locked out at 35*, and the motor loved it. It never hard started hot or exhibited detonation. I too wanted to add vacuum advance, and came across a relatively new distributor from Progressive Ignition that had a fully adjustable digital vacuum advance feature in terms of total added and at what vacuum. The rest of the distributor's timing adjustment was digital as well.

I now have the start timing set at 21, idle and total timing set at 35* and at high manifold vacuum it goes up to 42* with the addition of the vacuum advance.

I bought one and installed it last year. There is a small learning curve as far as set-up and dialing in, but it was quick and easy to learn, as I can see where the timing is in real time while driving the car around. Yes, I too follow the Four Seconds Flat method of hooking the advance to manifold vacuum.

Here's the link:

https://progressionignition.com/shop/ols/categories/chrysler


1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 3.91's (closest thing to an automatic 5 speed going)
Re: Is Vaccum Advance Really Such a Bad Idea [Re: fastmark] #2888131
02/14/21 01:39 PM
02/14/21 01:39 PM
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Originally Posted by fastmark
Originally Posted by Hemi_Joel
Every street engine will benefit from properly set up vacuum advance using non-ported manifold vacuum. Smoother, cleaner idle, better mileage, cooler running, longer life. You can plug it for racing. Drag race only engines should not have it.
I'm not saying nobody gets their car to run good on the street without vacuum advance, but you can make it run better and more efficiently at part throttle with it. Most of the time on the street is part throttle.


I am working on a 440 six pack with with the Promax metering block. It does not have the fitting in the metering block for the normal vacuum line for the distributor. Now that port on a stock metering block is ported, correct? Meaning it does not get vacuum at idle but at throttle, correct? So, I should run the vacuum line straight to manifold vacuum, right. I read on one of the Corvette forums and they were saying the first Tri powers had the vacuum advance straight to the manifold vacuum.
i believe the quickfuel aftermarket metering block does have a provision for a vacuum advance. might be worth looking at.

Re: Is Vaccum Advance Really Such a Bad Idea [Re: polyspheric] #2888154
02/14/21 02:00 PM
02/14/21 02:00 PM
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Originally Posted by polyspheric
For engines close to stock tune (any size, but mild cam) full vacuum to the distributor works well.
As the cam approaches 240 degrees @ .050", full vacuum works at idle, but as you open the throttle vacuum quickly dies, which reduces RPM, etc.
Ported fixes this, since idle is based solely on initial advance it's completely stable until a later throttle position.
You can even fab a new port position by inserting a small tube right through the casting to a point (generally slightly higher to delay vacuum) than the original, which will not add vacuum until slightly higher throttle disc angle. Hint: doesn't need to be horizontal.
Try both, keep the one that works best, cap the other (don't blank it), it may help the next time you change your tune-up.


Good point, but mostly applicable to stock initial timing settings. If you run your initial timing at 15 to 20°, where it should be for a performance motor, there's still plenty of advance to prevent the motor from bogging or stumbling when the vacuum advance goes away upon throttle tip in.

If you run ported vacuum to your advance can, you still have the same ignition timing at low vacuum conditions that you would with manifold vacuum, except you give up the clean idle.


[img]http://i.imgur.com/boeexFms.jpg[/img]
31 Plymouth Coupe, 392 Hemi, T56 magnum
RS23J71
RS27J77
RP23J71
RO23J71
WM21J8A
“Never argue with a fool; onlookers may not be able to tell the difference.” – Mark Twain
"Stay away from negative people. They have a problem for every solution."
Re: Is Vaccum Advance Really Such a Bad Idea [Re: Hemi_Joel] #2888215
02/14/21 03:18 PM
02/14/21 03:18 PM
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Bend,OR USA
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Cab_Burge Online work
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I started working is Service Station, AKA Gas stations in 1961 and learn most of what I learn to work on cars back then.
All the Chevy cars that came in for tune ups that i remember had manifold vacuum for the vacuum advances, you had to disconnect them and cap off the port to set the initial timing is what I remembering now work Not so on the Fords and Mopars shruggy
I do remember also that GM swap to ported vacuum some time after 1961 shruggy


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Is Vaccum Advance Really Such a Bad Idea [Re: polyspheric] #2888226
02/14/21 03:36 PM
02/14/21 03:36 PM
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West Plains, MO
DrCharles Offline
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Originally Posted by polyspheric
For engines close to stock tune (any size, but mild cam) full vacuum to the distributor works well.
As the cam approaches 240 degrees @ .050", full vacuum works at idle, but as you open the throttle vacuum quickly dies, which reduces RPM, etc.
Ported fixes this, since idle is based solely on initial advance it's completely stable until a later throttle position.


With a relatively small cam of 240@.050, that may be true. It's definitely not the case with my 272@.050 which idles at only 8" vacuum. Lumpy but stable with 27 degrees at idle.
The vacuum can doesn't even move at 8", but at cruise (15" Hg) it's advanced, which is exactly when the engine wants it. So it's working fine on manifold vac.

Everybody's setup is different and I agree experimenting is important.

Re: Is Vaccum Advance Really Such a Bad Idea [Re: DrCharles] #2888435
02/14/21 09:49 PM
02/14/21 09:49 PM
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for what it is worth, I agree on a street engine an advance curve is what you want to make it driveable. I approach it this way, I use an engine program, that among other things will calculate an advance curve for the engine combination that I have. It also calculates what rpm ranges detonation will be a problem. So if you don't have access to a distributor machine, the best way is to have a helper raise the rpm in 200 or so increments, use an adjustable timing light, note the timing on some graph paper and connect the dots. If you are using a vacuum advance I like one of those hand pumps with a gauge to see what the advance unit does. Then I change springs or what ever method the distributor uses to try and make my graph match the computer program recommendations. It usually is close. Then fine tune from there.

Re: Is Vaccum Advance Really Such a Bad Idea [Re: jwb123] #2888718
02/15/21 01:40 PM
02/15/21 01:40 PM
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About 15 years ago on here I had guys ready to fist fight over me merely saying it was good to run. Maybe after years of seeing others say it works people have seen the light. Been a few topics like that over the years on here.


I want my fair share
Re: Is Vaccum Advance Really Such a Bad Idea [Re: jbc426] #2888722
02/15/21 01:43 PM
02/15/21 01:43 PM
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Originally Posted by jbc426
I ran my RB locked out at 35*, and the motor loved it. It never hard started hot or exhibited detonation. I too wanted to add vacuum advance, and came across a relatively new distributor from Progressive Ignition that had a fully adjustable digital vacuum advance feature in terms of total added and at what vacuum. The rest of the distributor's timing adjustment was digital as well.

I now have the start timing set at 21, idle and total timing set at 35* and at high manifold vacuum it goes up to 42* with the addition of the vacuum advance.

I bought one and installed it last year. There is a small learning curve as far as set-up and dialing in, but it was quick and easy to learn, as I can see where the timing is in real time while driving the car around. Yes, I too follow the Four Seconds Flat method of hooking the advance to manifold vacuum.

Here's the link:

https://progressionignition.com/shop/ols/categories/chrysler


Those are really interesting and I believe you posted that before maybe last year. I’m interested in the durability of them since most anything electronic these days seems to fail easily. The features seem really cool on these.


I want my fair share
Re: Is Vaccum Advance Really Such a Bad Idea [Re: jbc426] #2888727
02/15/21 01:47 PM
02/15/21 01:47 PM
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Originally Posted by jbc426
I ran my RB locked out at 35*, and the motor loved it. It never hard started hot or exhibited detonation.

https://progressionignition.com/shop/ols/categories/chrysler


not every motor wants to crank over and start at 35 degrees locked. What was your compression ratio?


[img]http://i.imgur.com/boeexFms.jpg[/img]
31 Plymouth Coupe, 392 Hemi, T56 magnum
RS23J71
RS27J77
RP23J71
RO23J71
WM21J8A
“Never argue with a fool; onlookers may not be able to tell the difference.” – Mark Twain
"Stay away from negative people. They have a problem for every solution."
Re: Is Vaccum Advance Really Such a Bad Idea [Re: Hemi_Joel] #2888755
02/15/21 02:38 PM
02/15/21 02:38 PM
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Vac advance will work fine on ported or manifold, but it needs to be set up and tuned specifically for the method used.

It won't work to just move the vacuum line and call it a day.

Personally I used manifold vacuum on my truck. From memory, I have ~14° initial, plus around 20 mechanical (reduced/limited from what stock allowed), plus another 15ish via vac advance. During cranking it sees the initial 14 and starts well, then goes to 30 something. At part throttle cruise, they all add up to ~50 something. At wot, the vac advance drops out to the ~34 total. Keep in mind most vac cans can be adjusted as to what vacuum they drop out at, which also makes a difference and also needs to be tuned.

Works great, and really cleaned up my idle.

I think stock called for ~5 degrees initial timing, then had an enormous amount of mechanical advance, which must be limited if you want to run more initial.


If you ever find yourself in a fair fight, your tactics suck.
Re: Is Vaccum Advance Really Such a Bad Idea [Re: DaveRS23] #2888783
02/15/21 03:20 PM
02/15/21 03:20 PM
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I'll admit I never spent much time to try to dial in vacuum advance B/C I have had too many problems with those vacuum cans leaking.
I've run a quick curve for many years and it works all right, but there are improvements to be had that deserve a little more time and effort.

I have heard of overheating and fuel economy problems from not using it, but haven't really noticed much.

Originally Posted by DaveRS23
Maybe an episode of Engine Masters?


Seems like they run everything locked out?
Idle and WOT power on a dyno: "What else is there?" seems to be the attitude, LOL.
Dulcich/Frieburger both used to stop by here once in awhile, like 20 years ago.


Rich H.





Re: Is Vaccum Advance Really Such a Bad Idea [Re: ZIPPY] #2888940
02/15/21 09:23 PM
02/15/21 09:23 PM
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IL
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Originally Posted by ZIPPY
I'll admit I never spent much time to try to dial in vacuum advance B/C I have had too many problems with those vacuum cans leaking.
I've run a quick curve for many years and it works all right, but there are improvements to be had that deserve a little more time and effort.

I have heard of overheating and fuel economy problems from not using it, but haven't really noticed much.

Originally Posted by DaveRS23
Maybe an episode of Engine Masters?


Seems like they run everything locked out?
Idle and WOT power on a dyno: "What else is there?" seems to be the attitude, LOL.
Dulcich/Frieburger both used to stop by here once in awhile, like 20 years ago.


well, they did the long/short hemi intake comparison to look at area under the curve smile


70 Sport Fury
68 Charger
69 Coronet
72 RR
Re: Is Vaccum Advance Really Such a Bad Idea [Re: fatman] #2888953
02/15/21 10:03 PM
02/15/21 10:03 PM
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New York
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The dangerous part is when you have big vacuum advance, but it doesn't go off as quickly as you would like - result: destructive knock (even for a second or two).
Rather than tune it with an adjustable can (Crane etc.): a small air solenoid (I use Bimba, it's 3/4" OD, 1-7/8" long and cheap) in the hose right at the can shuts down in .1-.2 seconds when the micro-switch on your throttle linkage hits, or you can use a button on your shifter.
Yes, there will always be a delay while the plate relaxes to normal position, not sure if a stronger spring is OK.
For sustained light throttle cruising, 60 years ago J.C. Whitney, Warshawsky, Honest Charley, etc. used to sell a thumb wheel with a cable attached. Device goes on your dash, cable moves the advance plate through the original can's linkage hole. To use: watch your vacuum gauge and move it to get the highest reading. Depending on your cam and gearing, higher speed may need more or less advance. Yes, for those WOT bursts you have to invent a quick disengage so you don't have to thumb it 10 times.
If you like to fab, a mechanical solenoid can pull and release a similar cable from Position A (relaxed) to Position B (+20 degrees) instantly with a strong return spring. If it's on a bell-crank, different linkage holes allow choosing among several advance levels.
Cables: quality products only, lube well, only large bends, adjustable for slack. Your bike shop has some choices.


Boffin Emeritus
Re: Is Vaccum Advance Really Such a Bad Idea [Re: furious70] #2888961
02/15/21 10:13 PM
02/15/21 10:13 PM
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i doubt an engine dyno would give any real world info. setting up a performance curve with a vacuum advance isn't straight forward and seems to be specific to each engine/car/driving combo. i know i must've built more than 20 different combos, and still aren't perfectly satisfied with one engine combo. what works on one won't work on the other. i don't glean much from the magazine guys anymore. i do believe that the factory mopar distributor and factory vacuum units are the best to work with. finding usable springs and plates could be a challenge. the FBO plates i have are far from accurate. i don't think the general motors clone distributors are as flexible as factory mopar.

Re: Is Vaccum Advance Really Such a Bad Idea [Re: lewtot184] #2888980
02/15/21 11:06 PM
02/15/21 11:06 PM
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What I do is get the initial, mechanical, and total all dialed in for wide open throttle. Vacuum disconnected. Then hook up the vacuum and street drive it. Test part throttle pulls in various situations with the vacuum advance unrestricted and listen for pinging. Keep dialing it back a little and re-testing until it doesn't ping under any circumstance and you're done. Then disconnect and plug it when going racing.


[img]http://i.imgur.com/boeexFms.jpg[/img]
31 Plymouth Coupe, 392 Hemi, T56 magnum
RS23J71
RS27J77
RP23J71
RO23J71
WM21J8A
“Never argue with a fool; onlookers may not be able to tell the difference.” – Mark Twain
"Stay away from negative people. They have a problem for every solution."
Re: Is Vaccum Advance Really Such a Bad Idea [Re: furious70] #2889081
02/16/21 10:30 AM
02/16/21 10:30 AM
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Originally Posted by furious70
Originally Posted by ZIPPY
I'll admit I never spent much time to try to dial in vacuum advance B/C I have had too many problems with those vacuum cans leaking.
I've run a quick curve for many years and it works all right, but there are improvements to be had that deserve a little more time and effort.

I have heard of overheating and fuel economy problems from not using it, but haven't really noticed much.

Originally Posted by DaveRS23
Maybe an episode of Engine Masters?


Seems like they run everything locked out?
Idle and WOT power on a dyno: "What else is there?" seems to be the attitude, LOL.
Dulcich/Frieburger both used to stop by here once in awhile, like 20 years ago.


well, they did the long/short hemi intake comparison to look at area under the curve smile


.....at wide open throttle wink


Rich H.





Re: Is Vaccum Advance Really Such a Bad Idea [Re: hooziewhatsit] #2889116
02/16/21 11:34 AM
02/16/21 11:34 AM
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Windsor, ON, Canada
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Originally Posted by hooziewhatsit
Vac advance will work fine on ported or manifold, but it needs to be set up and tuned specifically for the method used.

Personally I used manifold vacuum on my truck. From memory, I have ~14° initial, plus around 20 mechanical (reduced/limited from what stock allowed), plus another 15ish via vac advance. During cranking it sees the initial 14 and starts well, then goes to 30 something. At part throttle cruise, they all add up to ~50 something. At wot, the vac advance drops out to the ~34 total.

Works great, and really cleaned up my idle.

You know, this seems like a great recipe well worth trying out. I can certainly appreciate cleaning up the idle situation, my 360 with just a 238@0.050 duration struggled with this for a long time. I re-worked the Carter TQ circuits which greatly improved this, but I bet there is still a little more left in there given that the engine would run ever-so-nicer with more advance at idle, and yet the problem with startup with that much initial advance would prevent me from going further.

Nice setup! punkrocka

Re: Is Vaccum Advance Really Such a Bad Idea [Re: Hemi_Joel] #2889142
02/16/21 12:13 PM
02/16/21 12:13 PM
Joined: Mar 2007
Posts: 3,117
West Coast, USA
jbc426 Offline
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Originally Posted by Hemi_Joel
Originally Posted by jbc426
I ran my RB locked out at 35*, and the motor loved it. It never hard started hot or exhibited detonation.

https://progressionignition.com/shop/ols/categories/chrysler


not every motor wants to crank over and start at 35 degrees locked. What was your compression ratio?


True. My RB is calculated to be 10.2 to 1. It cranks 200 psi. Same ratio and cranking compression on my 408 Magnum. Both are high quench.


1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 3.91's (closest thing to an automatic 5 speed going)
Re: Is Vaccum Advance Really Such a Bad Idea [Re: SomeCarGuy] #2889146
02/16/21 12:16 PM
02/16/21 12:16 PM
Joined: Mar 2007
Posts: 3,117
West Coast, USA
jbc426 Offline
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West Coast, USA
Originally Posted by SomeCarGuy
Originally Posted by jbc426
I ran my RB locked out at 35*, and the motor loved it. It never hard started hot or exhibited detonation. I too wanted to add vacuum advance, and came across a relatively new distributor from Progressive Ignition that had a fully adjustable digital vacuum advance feature in terms of total added and at what vacuum. The rest of the distributor's timing adjustment was digital as well.

I now have the start timing set at 21, idle and total timing set at 35* and at high manifold vacuum it goes up to 42* with the addition of the vacuum advance.

I bought one and installed it last year. There is a small learning curve as far as set-up and dialing in, but it was quick and easy to learn, as I can see where the timing is in real time while driving the car around. Yes, I too follow the Four Seconds Flat method of hooking the advance to manifold vacuum.

Here's the link:

https://progressionignition.com/shop/ols/categories/chrysler


Those are really interesting and I believe you posted that before maybe last year. I’m interested in the durability of them since most anything electronic these days seems to fail easily. The features seem really cool on these.


Time will tell, but so far so good. I keep my MSD stuff in the trunk just in case.


1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 3.91's (closest thing to an automatic 5 speed going)
Re: Is Vaccum Advance Really Such a Bad Idea [Re: polyspheric] #2889169
02/16/21 12:42 PM
02/16/21 12:42 PM
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Originally Posted by polyspheric
The dangerous part is when you have big vacuum advance, but it doesn't go off as quickly as you would like - result: destructive knock (even for a second or two).
Rather than tune it with an adjustable can (Crane etc.): a small air solenoid (I use Bimba, it's 3/4" OD, 1-7/8" long and cheap) in the hose right at the can shuts down in .1-.2 seconds when the micro-switch on your throttle linkage hits, or you can use a button on your shifter.
Yes, there will always be a delay while the plate relaxes to normal position, not sure if a stronger spring is OK.
For sustained light throttle cruising, 60 years ago J.C. Whitney, Warshawsky, Honest Charley, etc. used to sell a thumb wheel with a cable attached. Device goes on your dash, cable moves the advance plate through the original can's linkage hole. To use: watch your vacuum gauge and move it to get the highest reading. Depending on your cam and gearing, higher speed may need more or less advance. Yes, for those WOT bursts you have to invent a quick disengage so you don't have to thumb it 10 times.
If you like to fab, a mechanical solenoid can pull and release a similar cable from Position A (relaxed) to Position B (+20 degrees) instantly with a strong return spring. If it's on a bell-crank, different linkage holes allow choosing among several advance levels.
Cables: quality products only, lube well, only large bends, adjustable for slack. Your bike shop has some choices.
i took a que from the factory distributors and use a primary/secondary mech advance to stage the mech timing. the factory vacuum cans are adjustable and that's a big help. i also limit the amount of vacuum advance in the units to try to keep total for mech and vacuum to about 50degrees. i adjust the vacuum opening to around 10" of vacuum so anything under 10" diminishes the vacuum advance quickly. a fly in the ointment here is there are 3 different types of springs used in the canisters. i much prefer the 9 degree factory units over any aftermarket and they use the medium spring. so far this works for what i have but i think the key to all this is how much vacuum the engine makes. my experience has been the higher vacuum (stock type engines) are more temperamental than lower vacuum performance engines.

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