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Vacuum advance benefits? |
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69 ambassador 390
Supporter of TheAMCForum Joined: Nov/22/2009 Location: Peoria, AZ Status: Offline Points: 3539 |
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Pretty good article but off in some areas. Hc emissions are actually reduced with the advanced idle but NOX emissions are increased. The ported signal is not created in the venturi but in the throat of the carb just above the plates. He is correct on Cannister set up. The reason to run ported is exectly that it has no signal at idle. This allows more initial. The oems used various pvs and check valves to allow more vac advance from manifold during both warm up and then when overheated also. This was the reason for the air inlet temp valves and the two ported swithces on our AMCs. I'm not sure a G.M. engineer is the right guy to listen to. Have you ever driven the late seventies or early eighties crap they produced? Find an AMC engineer to listen to. They had the most advanced yet uncomplicated systems on carbs right up until the last one in 1991. The 91 wagoneer had the highest mileage of any full size vehicle and they were the only one running a carb. If you are running a street car and don't run all the valves that control the mix of ported to manifold signal than you should run only ported on the street. But in the end, run what you want. More people run ported than manifold no matter what make you have. FACT. The reason is it works better. Remember when people thought the world was flat or the center of the universe. Experts argued that it was true even in the face of overwhelming evidence to the contrary. And they weren't stupid people. They were smart people who were wrong.
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Steve Brown
Algonac, Mi. 69 Ambassador sst 390 84 Grand Wagoneer 69 Cougar XR7 65 Fairlaine 500XL 79 F-350 Super Camper Special |
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Red Devil
AMC Addicted Joined: Jul/10/2007 Location: Canada Status: Offline Points: 1743 |
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.... you mean the world isn't flat and we're not the centre of the universe ... say it ain't so
Understanding is manifold and ported vacuum are the same above idle, once the the throttle blades are open enough to expose the ported vacuum port. So the debate about manifold vs. ported vacuum is mostly about idle / off idle.
If you've got a lumpy cam or very little initial timing, manifold vacuum may help idle and transition to part throttle ... or you could just run more initial timing. Problem with using manifold vacuum is idle vacuum may not be too stable, so timing may jump around and become erratic. This is where using a vacuum advance unit that's fully deployed at less than idle vacuum will help ... but it will have limited ability to fine tune advance at varying loads and throttle openings at higher rpms like ported, if using a vacuum advance unit with higher vaccum setting @ full advance.
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Bowtie70SS
AMC Apprentice Joined: Jun/19/2010 Location: Cincinnati Status: Offline Points: 245 |
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www.fueleconomy.gov In 1991 the Grand Wagoneer got 11mpg city and 12mpg hwy Dodge Ramcharger 11city 12hwy while the Blazer got 13 city 15hwy, the Ford Bronco got 12mpg city and 15hwy. The Suburban got 12city 15hwy. Not hatin on Jeeps but they weren't the most fuel efficient according to the EPA.
Edited by Bowtie70SS - Nov/24/2011 at 1:22pm |
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69 ambassador 390
Supporter of TheAMCForum Joined: Nov/22/2009 Location: Peoria, AZ Status: Offline Points: 3539 |
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You are correct sir. That is why there is no reason to run manifold vac at all. It's during the transitions that ported comes into play. And what has not been said so far is that the speed of the burn remains virtually constant no matter what rpm we are at. What does change is the time for it has to burn. At higher rpms there is simply less time to complete the burn and thus we need more advance. This condition is usually encountered at or near WOT and the vac. signal is low. This is where the centrifigal comes into play. Most conditions in normal driving the ported vac. runs the show. Also, the vacume advance can't pull more than the breaker plate allows, so again a properlt designed set up works best. Put the limiters were they belong.
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Steve Brown
Algonac, Mi. 69 Ambassador sst 390 84 Grand Wagoneer 69 Cougar XR7 65 Fairlaine 500XL 79 F-350 Super Camper Special |
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69 ambassador 390
Supporter of TheAMCForum Joined: Nov/22/2009 Location: Peoria, AZ Status: Offline Points: 3539 |
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Steve Brown
Algonac, Mi. 69 Ambassador sst 390 84 Grand Wagoneer 69 Cougar XR7 65 Fairlaine 500XL 79 F-350 Super Camper Special |
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Bowtie70SS
AMC Apprentice Joined: Jun/19/2010 Location: Cincinnati Status: Offline Points: 245 |
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A 6cyl is available in only the Cherokee and it was rated at 16 and 18 while a full size 4.3 Chevy truck was 16 and 18. Commendable but it doesn't exactly leave the others in the dust.
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turbo
AMC Addicted Joined: Oct/26/2008 Location: chicago area Status: Offline Points: 2566 |
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man, that article above NEEDS to be made a sticky, BIG TIME. Great overview that needs to be revisited from time to time to stay current unless you're doing this EVERY DAY and even then I think the builders need to sometimes be reminded. trust me I have had some great builders and some pogues that I would not let work on my lawnmower. so how bout that sticky?
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they call me Capt RETIRED!
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69 ambassador 390
Supporter of TheAMCForum Joined: Nov/22/2009 Location: Peoria, AZ Status: Offline Points: 3539 |
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The Grand Wagoneer was offered in Base or Limited trim levels in two and four door models and was built with a 6 Cylinder, 4.2 Liter,102 Horsepower engine. There was also a V8 engine available as an option for the single trim Grand Wagoneer. The Grand Wagoneer was offered in ten colors. The 1991 model was available with a "Final Edition" badge on the dashboard.
Despite its advancing age the Grand Wagoneer remained popular. Instrument panel, grille, and tail lamps were redesigned for 1986, followed by minor revision to the wood grained sides in 1987, the year that ownership of the company passed to Chrysler Corporation. Chrysler largely left the Grand Wagoneer alone, and even continued to build the Grand Wagoneer with the carbureted AMC V8 instead of its own, and arguably, more modern fuel-injected V8s. Year-to-year changes were minimal; Chrysler added new features such as an overhead console taken from Chrysler's popular minivans and a rear-window wiper/washer system for 1989, but otherwise new model years through 1991 were marked only by new paint colors. |
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Steve Brown
Algonac, Mi. 69 Ambassador sst 390 84 Grand Wagoneer 69 Cougar XR7 65 Fairlaine 500XL 79 F-350 Super Camper Special |
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turbo
AMC Addicted Joined: Oct/26/2008 Location: chicago area Status: Offline Points: 2566 |
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they call me Capt RETIRED!
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69 ambassador 390
Supporter of TheAMCForum Joined: Nov/22/2009 Location: Peoria, AZ Status: Offline Points: 3539 |
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I actually had the dates wrong. The sixs got huge mileage for a full size vehicle. I found this from a little research. Note, this is a carbed enging with vac. advance. From Alpars.com, history of Jeep Wagoneer. My own experience with a six wagoneer supports this. They actually had more bottom end grunt than the V8s.
" 1983 continued with few changes; the Wagoneer was available only in the Brougham and Limited models. A 4.2 liter six or 5.9 liter V8 were available, both with two-barrel carbs; the V8 was not available in California; and automatic transmissions were standard. The Wagoneer Six was rated at 18/23 mpg, the V8 at 13/18 mpg.
The Cherokee was sold in two-door base, Pioneer, Chief, and Laredo models, with the standard 258 cid (4.2 liter) six or 360 V8, both carrying a two-barrel carb; gas mileage was 18/24 for the six, 14/20 for the V8 (presumably tested with the four-speed manual). The V8 was no longer available in California. Based on Cherokee gas mileage, the "automatic transmission penalty" was roughly 1 mpg for the six and 2 mpg for the V8."
Edited by 69 ambassador 390 - Nov/24/2011 at 2:54pm |
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Steve Brown
Algonac, Mi. 69 Ambassador sst 390 84 Grand Wagoneer 69 Cougar XR7 65 Fairlaine 500XL 79 F-350 Super Camper Special |
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