Author Topic: vacuum location for advance canister  (Read 1233 times)

boomer632

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vacuum location for advance canister
« on: March 29, 2023, 02:46:46 PM »
I have a Pertronix distributor which has the advance canister. My vacuum line runs from the distributor to the carb base plate as seen in the pic. The rubber line has the white stripe and transitions to metal line then back to rubber as seen in lower left of picture. Would this vacuum source be considered "ported vacuum" or "manifold vacuum?
« Last Edit: March 29, 2023, 03:09:50 PM by boomer632 »
69 SS 06A X66 L78 M22 BU

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Re: vacuum location for advance canister
« Reply #1 on: March 29, 2023, 02:51:19 PM »
Ported.  Full vacuum is what choke vacuum and your brake booster sees and/or trans if equipped.  Looks like you have a capped T on the choke already.  If you wanna go to full vacuum just disconnect the ported hose and add into choke T.  Remember to cap the ported vacuum tube on the carb.



Doing a search on the main page of the forum you will see several threads that discuss this topic.  Here is one example.


JohnZ post: "Timing 101"


Also rotated your photo.

boomer632

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Re: vacuum location for advance canister
« Reply #2 on: March 29, 2023, 03:23:54 PM »
Yes I read that and the directions for my distributor say to use ported source which conflicts what John says. Wanted to make sure of what I had set up now. I didnt install the distributor so I was just gathering knowledge on how I should have it set up.
69 SS 06A X66 L78 M22 BU

Stingr69

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Re: vacuum location for advance canister
« Reply #3 on: March 29, 2023, 07:30:29 PM »
It's about factory "correct" or "better running".  Factory correct is hooked up to a carburetor "ported" nipple.  Better running would not use "ported".  You might need to do some reading on the subject and decide which way you want to go. 

Stingr69

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Re: vacuum location for advance canister
« Reply #4 on: March 29, 2023, 07:34:10 PM »
If you choose to have a better running engine, you may need to select a different cannister.  If you know how much vacuum you are pulling at idle, you can select an optimal canister. 

boomer632

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Re: vacuum location for advance canister
« Reply #5 on: March 30, 2023, 06:18:29 PM »
pertronix tech replied back to me and said hook VA to ported source only. Full manifold source will damage diaphragm.
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KurtS

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Re: vacuum location for advance canister
« Reply #6 on: April 13, 2023, 05:36:31 AM »
I call BS. The VA can see a much higher vacuum under a decel - ported or not.
Kurt S
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rich69rs

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Re: vacuum location for advance canister
« Reply #7 on: April 13, 2023, 07:01:29 PM »
I call BS. The VA can see a much higher vacuum under a decel - ported or not.

Agree

Been running manifold vacuum on my distributor (with Pertronix/eliminated the points) since 2005 - works great - no issues.

Richard
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PHAT69AMX

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Re: vacuum location for advance canister
« Reply #8 on: May 05, 2023, 11:54:50 PM »
If I understood David Vizard, the leaner the mixture, the slower it burns.  So earlier Vac Adv was on Manifold Vacuum.  The "Emissions" came into play, so the did what they "had to" instaed of "what the engine wanted".  The wanted less HC's out the pipe at idle.  So they opened the carburetor wider at idle to let in more air, more O2, cleaner burn.  But then the idle speed was way to high.  So they came up with PORTED VACUUM on the Vac Adv so that it was NOT deployed at idle, and the further opened carb let in more air and O2, and tailpipe HC's were decresed, but the engines hated it...

169INDY

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Jim
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69 Pace Car L48 Th-350 LOS
68 Z28 M21 LOS

169INDY

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Re: vacuum location for advance canister
« Reply #10 on: June 08, 2023, 06:49:58 AM »
To add to STNGR69 Comments. (Reply#4)
Here is some text  Credit Link Here: https://www.crankshaftcoalition.com/wiki/images/e/e4/Vacuum_Advance_Specs.pdf

Does your engine require additional timing advance at idle in order to idle properly? Radical cams will often require
over 16 degrees of timing advance at idle in order to produce acceptable idle characteristics. If all of this initial
advance is created by advancing the mechanical timing, the total mechanical advance may exceed the 36-degree
limit by a significant margin. An appropriately selected vacuum advance unit, plugged into manifold vacuum, can
provide the needed extra timing at idle to allow a fair idle, while maintaining maximum mechanical timing at 36. A
tuning note on this: If you choose to run straight manifold vacuum to your vacuum advance in order to gain the
additional timing advance at idle, you must select a vacuum advance control unit that pulls in all of the advance at a
vacuum level 2 below (numerically less than) the manifold vacuum present at idle. If the vacuum advance control
unit is not fully pulled in at idle, it will be somewhere in its mid-range, and it will fluctuate and vary the timing
while the engine is idling. This will cause erratic timing with associated unstable idle rpm. A second tuning note
on this: Advancing the timing at idle can assist in lowering engine temperatures. If you have an overheating
problem at idle, and you have verified proper operation of your cooling system components, you can try running
manifold vacuum to an appropriately selected vacuum advance unit as noted above. This will lower engine temps,
but it will also increase hydrocarbon emissions on emission-controlled vehicles. Running straight manifold vacuum
to the vacuum advance control unit is recommended for most applications where emissions are not an immediate
concern
Jim
68 SS/RS L35 Th-400 LOS
69 Pace Car L48 Th-350 LOS
68 Z28 M21 LOS