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Distributor 1967 to 1974 Application Info |
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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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Vacuum advance was first used by Chrysler in about 1939 - and not for economy but for driveability. It helped make up for the lean mix cause during acceleration from idle to off-idle when the sudden rush of air beat the fuel into the chamber - thus it was ported. Touch the throttle, suddenly you lean the mix out but at the same time Chrysler added a touch of advance via ported vacuum advance and helped to compensate.
Since then it's been used for a multitude of things - by tweaking how, when, how much and so on, vacuum gets applied and how much advance it gives - and to toss another wrench into the mix - there's also times venturi vacuum has been used on the advance - and that INCREASES while manifold vacuum DROPS with heavy throttle, etc. Ford used ported vacuum advance within a year or two of Chrysler introducing it - and at that time, economy wasn't a concern, neither was "pollution" - it was for smoother operation and tweaking the spark timing to get rid of flat spots and compensate for certain lean times. I've over-simplified it a bit but somewhere I gave a whole lot more history on it, its use and so on. I even have some photos of some original engines from about 1940 or so that show it being used and connected to ported vacuum at the carburetor. I really wish I could find that book again that told of the detailed development of vacuum and mechanical advance. I've tried but can't find my original sources - the book, and a magazine article, on the invention of and advancement of the use of vacuum advance - who did it, when and why.
Not only do high-performance engines with lumpy cams not have much vacuum at lower speeds, part throttle, etc. - there is precious little concern for a bit of a blah feeling when coming off idle - if you'd even notice that with 'em. You are already running more RPM and are likely beyond that spot anyway. |
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Lyle
AMC Addicted Joined: Jul/17/2014 Location: None Status: Offline Points: 772 |
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This is one of several articles:
I have an old book, John Deere training manual, that has history and detail but it's not online. It basically states the information above. Some will agree and some not. Electronics have made many of these systems obsolete.
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purple72Gremlin
AMC Addicted Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16591 |
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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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That gm engineer thing has been debunked and in some cases laughed at by.....gm people. No one was ever able to validate the person ever existed plus there's too much historical evidence to the contrary. The problem is that it was copied, repeated, posted so many times it became like so much on the web - it's everywhere so it must be true. When there are cars made in 1940 that have vacuum advanced connected by steel line to the carb above the throttle, well...... And I've been an engine history buff for more years than a third of our members have been alive.
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Lyle
AMC Addicted Joined: Jul/17/2014 Location: None Status: Offline Points: 772 |
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You mean this article: Search "www.camaros.org/pdf/timing101.pdf" By John Hinckley
Edited by Lyle - Apr/15/2018 at 4:33pm |
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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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The bottom line is that vacuum advance was first used by Plymouth (I tend to use "Chrysler" generically, but Plymouth was first, followed by Ford just a year or so later.
It was ported to overcome the issue of "lag" or hesitation due to the lean mixture hitting the combustion chamber - it advanced the timing to compensate for or hide the lag caused by the lean mixture. It was nothing at all to do with emissions (are you kidding me - 1939-1940?) and nothing to do with economy (again, huh? With gas cheap and plentiful) It was the era where the car makers were advertising to every Tom, Dick and Harry and their WIVES. Women were driving, non-farmers were driving. Doctors, lawyers, bankers, wifes, mothers, everyone was driving and the car makers were now concerned with EASE of starting, running, and smooth power.
The idea was to control timing automatically (having gotten rid of the spark timing lever save for a few applications - some equipment still had such levers) and make driving simple and easy for all. People were complaining of rough running, rough rides, hard to shift vehicles and with the growth of driving in the cities already exploding in the prior decades, drivers were faced with traffic controls and stop and go driving.. Connecting the vacuum advance they had just invented to ported vacuum meant the timing got a quick burst of advance at the same time the mixture leaned out - getting rid of the lag or hesitation. In fact in the early years, 1940 on, all vacuum advance devices were connected to ported vacuum. It was via steel lines. Now to point out true BS in too many of those so-called "expert" write-ups, by so-called engineers...... Here's a great example - >> Now to the widely misunderstood manifold vs. ”ported” vacuum aberration. After 30-plus years of controlling vacuum advance systems with full manifold vacuum, that “free” indicator of engine load and fuel mixture, along....<< Sorry, dude, they were NOT controlled with manifold vacuum. For one thing depending on the date he wrote this or is referring to as his "after 30 plus years..." he'd be talking about roughly 1970 - and even in the 60s cars used ported vacuum -so he's showing lack of knowledge even there. Assume the first system was 1940 to keep the math simple - his 30 plus years would put his point of reference in 1970 or later - and he'd better check my 70 Javelin, my brother's 69 - and even further back - all ported vacuum. The guy likely never saw a car built before 1960 in his life - or at least never worked on one. I have - I've worked on engines built from the turn of the last century (just after 1900) all the way up, the 1930s, 40s, etc and can walk an eight of a mile to a street rodder who has a shop full of the early engines. The article was filled with errors. It would take me hours to go through every version out there and point out all of the issues - but the biggest glaring issue is his contention that vacuum advance was manifold vacuum in the days before emissions, etc. - BULL CRAP. I have PHOTOS to prove it - and one of these days I'll find my documentation and point it out in black and white. I don't care how many sites repeat the same BS - it doesn't make it more true the more times it's repeated. He's got other factual errors in there, too - it reads to me more like an amateur trying to sound impressive and scientific than it does actually pointing out hard facts. But then since it's been out there for years and copied hundreds of times and reposted over and over as fact, it will be believed and it's hard to fight computer generated facts - made facts simply because the name is out there hundreds of times and he sounds like he knows. |
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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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OK so I was off a decade - Plymouth actually did the vacuum advance in 31, not 41
It was introduced when they introduced a "free-wheeling" easier to shift transmission (again, for non-farmers women, etc.) Literature from the period explains what I was alluding to - or even saying, but here's a quote from a place dedicated to Plymouth from the 30s and 40s - understand this is taken from period literature and paraphrased so it's not exactly technical and is grossly over-simplified to be sure - but again, it's about ported vacuum and helping driveability - Plymouth introduced a freewheeling transmission to make shifting easier. As part of that introduction they found they needed to add some sort of automatic spark advance control, so they added a vacuum advance. Period literature indicates that they had issues with the engine stalling without the automatic advance. - The purpose of the vacuum advance is to compensate for fast throttle opening movement from idle. - A failed vacuum advance will exhibit a lag when the throttle is snapped open from idle.
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5903 |
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Thu Apr 19, 2018, Updated Chart Uploaded and Posted
Thank You 67 Marlin & all others for the info.
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5903 |
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Many found useful the AMC DELCO TYPE DISTRIBUTOR APPLICATION CHART,
2nd post in this thread, and contributed to it's content. Chart revised/updated April 2018. This thread was a "Sticky" for like 10 years or so, but now no longer is for some reason. PM's sent pointing this out, yet it remains unremedied. Suggest users that find the Chart useful save / download it.
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PHAT69AMX
AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5903 |
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Still think this thread deserves "STICKY STATUS" re-instated like it was for 10 years
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