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Re: Best way to limit vacuum advance [Re: AndyF] #2418627
12/14/17 07:54 PM
12/14/17 07:54 PM
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dogdays Offline
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In the future, if you are working on a Firecore distributor and want advice, it would help if you mentioned right off the bat that it was a Firecore.

Rick, aka Sparky, AKA Sunroof GTX, IS Firecore, or at least a good part of Firecore. So if he has a comment it would behoove you pay attention.

I agree that the use of springs and vacuum pots is much akin to witchcraft. It is true, also, that electronically setting advance is another level of witchcraft. Electronic setting has one advantage over the spring/slot witchcraft and that is this: You don't have to understand how the black box works, you just have to understand that it does work.

R.

Re: Best way to limit vacuum advance [Re: pjc360] #2418635
12/14/17 08:04 PM
12/14/17 08:04 PM
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Chicago, IL
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PLUM_72 Offline
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Is vacuum advance really needed? If so Why?


1972 Dodge Challenger
Re: Best way to limit vacuum advance [Re: PLUM_72] #2418679
12/14/17 09:14 PM
12/14/17 09:14 PM
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Kirkland, Washington
Pacnorthcuda Offline
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Originally Posted By PLUM_72
Is vacuum advance really needed? If so Why?


It provides additional advance at part throttle conditions when the engine can take the advance (the additional advance would cause pinging at wide open throttle).

The additional advance increases the engine efficiency at part throttle, does not affect WOT.

Re: Best way to limit vacuum advance [Re: pjc360] #2418748
12/14/17 11:24 PM
12/14/17 11:24 PM
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Oregon
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AndyF Offline
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Oregon
This is another reason to think about moving to EFI. Even the cheap EFI systems available these days can control the ignition and they have vacuum advance built in since the EFI system needs to know manifold vacuum. I helped install a low dollar MSD Atomic system the other day and it had vacuum advance built in. The nice thing about EFI is that you can program the vacuum advance for both rate and total amount.

Re: Best way to limit vacuum advance [Re: pjc360] #2419123
12/15/17 06:25 PM
12/15/17 06:25 PM
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Chicago, IL
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PLUM_72 Offline
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I was curious on vacuum advance as the new FBO distributors have vacuum advance. Their mod years ago was adjusting the advance profile and eliminate vacuum advance on the distributor.


1972 Dodge Challenger
Re: Best way to limit vacuum advance [Re: PLUM_72] #2420783
12/19/17 02:41 AM
12/19/17 02:41 AM
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Houston,Tx.
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Lee446 Offline
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To limit the vacuum advance arm travel, I set my initial where I want it, use a timing light and a mighty vac hand pump to pull in an additional 10* and note the amount of vac required for the 10*, pop the cap off, pump the vac to noted amount, mark the vac advance arm with a sharpie right where it passes through the housing, pick a appropriately sized short roll pin and drill the correct sized hole through the arm where you marked it. Drive the pin in and you now have a mechanical stop on the vac advance.

Re: Best way to limit vacuum advance [Re: Lee446] #2420798
12/19/17 03:11 AM
12/19/17 03:11 AM
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Lincoln Nebraska
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^^^ Ding ding ding I do believe we have a winna.


live every 24 hour block of time like it's your last day on earth
Re: Best way to limit vacuum advance [Re: pjc360] #2422202
12/22/17 04:02 AM
12/22/17 04:02 AM
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Affton MO
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qwkmopardan Offline
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Affton MO
Put a 5/32" ball in the vacuum hose. Vacuum advance worthless.

Re: Best way to limit vacuum advance [Re: qwkmopardan] #2422320
12/22/17 02:58 PM
12/22/17 02:58 PM
Joined: Sep 2003
Posts: 19,239
north of coder
moparx Online content
"Butt Crack Bob"
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north of coder
i like vacuum advance on anything that sees any street time. if the hose is just removed or plugged, the tune is not complete. take the time to add/subtract any advance you can use [with what ever method you choose], and you will be happy you took the time to do so.
beer

Re: Best way to limit vacuum advance [Re: moparx] #2423217
12/24/17 07:07 PM
12/24/17 07:07 PM
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Houston,Tx.
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Lee446 Offline
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Houston,Tx.
I recently worked over the older MP electronic distributor in my friends GTX. With a Lunati Voodoo hydraulic FT,mildly ported 906 heads and a Holley SD with a 750 AFB, it was a bit sluggish on the bottom end. I put the FBO limiting plate and springs in it, and adjusted the vac advance for an additional 10* at idle. The difference was amazing, super sharp on the throttle response and my friend had to relearn how to take off from a light without spinning the tires. If you follow FBO's instructions, you can get your dist squared away and the advantages of having a vacuum advance that works properly will be obvious. My buddy said he picked up a little mpg to boot!

Re: Best way to limit vacuum advance [Re: Lee446] #2423241
12/24/17 08:09 PM
12/24/17 08:09 PM
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Posts: 9,866
Weddington, N.C.
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Easy way to do it on an old Mopar Distributor is to wedge a piece of ~.1-.125 header gasket material between the pin and the slot, takes out about 10-12 degrees of centrifugal and if done properly it can't go anywhere because the pins sling against it as the distributor speeds up. You could weld up the slot but back in the day this was easier. This allowed to advance the distributor and keep the total timing ~34-36 degrees.

It's real good and easy to try to see if it makes the difference you need, you could always weld the slot up later if you want.


WIZE

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