Re: Vacuum advance
[Re: volaredon]
#2499149
05/22/18 05:43 PM
05/22/18 05:43 PM
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Joined: Jul 2011
Posts: 817 Eugene, Oregon
Secret Chimp
super stock
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super stock
Joined: Jul 2011
Posts: 817
Eugene, Oregon
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That means it can pull up to 11.5 degrees in the distributor at full vacuum, or 23 degrees at the crank.
The old one (before it blew) was pulling 17 degrees at the crank at full vacuum, unless it had an internal hex adjuster and was set to something lower.
1967 Dodge Coronet Deluxe station wagon
1.03" T-bars, QA1 arms/rods, Cordoba/GM Metric/Volare brake & knuckle, XHDs, Hellwig rear sway, 318 Magnum w/ air gap, 727, 3.23s
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Re: Vacuum advance
[Re: Secret Chimp]
#2499719
05/23/18 10:57 PM
05/23/18 10:57 PM
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Joined: Jan 2008
Posts: 2,196 ILLINOIS
volaredon
OP
top fuel
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OP
top fuel
Joined: Jan 2008
Posts: 2,196
ILLINOIS
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That means it can pull up to 11.5 degrees in the distributor at full vacuum, or 23 degrees at the crank.
The old one (before it blew) was pulling 17 degrees at the crank at full vacuum, unless it had an internal hex adjuster and was set to something lower. I think you have this backwards. the old one was the 11.5. I have seen the allen screw adjuster in the vac nipple on vac advance cans before. what does this adjust? Can I make the 8.5 act like the 11.5? Does it change the inches of vacuum that it kicks in at? or same amount of degrees of advance, regardless of where the setscrew is adjusted, at a different vac level or RPM or load?
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Re: Vacuum advance
[Re: volaredon]
#2499726
05/23/18 11:06 PM
05/23/18 11:06 PM
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Joined: Jul 2011
Posts: 817 Eugene, Oregon
Secret Chimp
super stock
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super stock
Joined: Jul 2011
Posts: 817
Eugene, Oregon
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That means it can pull up to 11.5 degrees in the distributor at full vacuum, or 23 degrees at the crank.
The old one (before it blew) was pulling 17 degrees at the crank at full vacuum, unless it had an internal hex adjuster and was set to something lower. I think you have this backwards. the old one was the 11.5. I have seen the allen screw adjuster in the vac nipple on vac advance cans before. what does this adjust? Can I make the 8.5 act like the 11.5? Does it change the inches of vacuum that it kicks in at? or same amount of degrees of advance, regardless of where the setscrew is adjusted, at a different vac level or RPM or load? The adjuster determines how much vacuum you need to start pulling advance and what the ultimate maximum is. Basically, you are adjusting a vacuum vs spring resistance curve. You can't make the 8.5 act like the 11.5, but you could squinch an 11.5 down to act kind of like an 8.5. Whenever I monkey with this stuff, I like referring to this topic: http://www.dodgecharger.com/forum/index.php?topic=14888.0It has very good detail and an example table showing changes for going CW vs CCW with an example canister - once you have a Mityvac-type thing and a timing light on the engine, it is pretty quick to figure out your ideal adjustment.
Last edited by Secret Chimp; 05/23/18 11:06 PM.
1967 Dodge Coronet Deluxe station wagon
1.03" T-bars, QA1 arms/rods, Cordoba/GM Metric/Volare brake & knuckle, XHDs, Hellwig rear sway, 318 Magnum w/ air gap, 727, 3.23s
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Re: Vacuum advance
[Re: volaredon]
#2499789
05/24/18 01:01 AM
05/24/18 01:01 AM
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Joined: Feb 2010
Posts: 1,645 Phila. Pa.
Mattax
top fuel
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top fuel
Joined: Feb 2010
Posts: 1,645
Phila. Pa.
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I have seen the allen screw adjuster in the vac nipple on vac advance cans before. what does this adjust? Can I make the 8.5 act like the 11.5? Does it change the inches of vacuum that it kicks in at? or same amount of degrees of advance, regardless of where the setscrew is adjusted, at a different vac level or RPM or load?
The answer is maybe. Of the three variables, the spring rate can not be changed. The pre-load (allen adjuster) changes the vacuum need for the advance to start. The maximum advance is limited by the tabs on the arm. https://www.forabodiesonly.com/mopar/ams/how-to-limit-and-adjust-chrysler-vacuum-advance-cans.183/
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