Carter AVS mileage?
#1031081
07/12/11 04:37 PM
07/12/11 04:37 PM
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Joined: Jan 2003
Posts: 3,967 S.I. N.Y.
1MYTGTX
OP
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Joined: Jan 2003
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Took my first long trip on the highway using my newly restored "correct" 4640SA Carter AVS carb and got horrible gas mileage with it on the highway.....just a touch over 10mpg! Averaging about 70mph/3100 rpm the whole way. With my Holley 750 vac secondary carb with the HP main body, I was averaging about 15+ mpg......I think its time to switch back to my Holley....carb has been trouble since I put it on....have a pretty bad off idle stumble that I cant get rid of either.... Anyone else notice this with their Carters? Wasnt looking to get any better mileage out of it....just an observation over my Holley
1MYTGTX
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Re: Carter AVS mileage?
[Re: dogdays]
#1031083
07/12/11 10:05 PM
07/12/11 10:05 PM
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Joined: Jun 2005
Posts: 2,507 Royersford, PA
bschargerse
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Royersford, PA
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Chris,
I have the AVS from my '69 Charger on my Newport. Last year going to Carlisle I got close to 20mpg with the A/C off. But my car has a stock 383, with the iron '69 intake, and pertronix ignition, 2.76 gears. And I like to open up the secondaries LOL. I notice mine will stumble off idle if I floor it, but if I ease into it, then nail it, it's fine. I didn't check my mileage this year since the ignition was giving me fits. This carb sat for over 15 years, all I did was throw a rebuild kit on it and install it. I was thinking maybe you are under-carbed based on the size camshaft you are using.
To add, I was just reading a magazine article from back in '03 that Mopar Muscle did when they built both a 383 and a 440 to Magnum specs. One of the things noticed on the dyno test on the 440 was that the AVS was becoming a restriction, since at WOT there was 1.4 in. Hg of vacuum. They bolted on a Holley 850 vac secondary carb, and horsepower and torque jumped by 10, and the peak HP was 200 rpm higher. This was with a stock cam, iron intake, and exhaust manifolds.
Just food for thought. I hope this helps.
Last edited by bsakal; 07/12/11 10:15 PM.
Brian - 1971 Dodge Challenger "The Dodge, which was practically stock, just left the Mustang like you wouldn't believe."
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Re: Carter AVS mileage?
[Re: bschargerse]
#1031084
07/12/11 10:18 PM
07/12/11 10:18 PM
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Joined: Jan 2003
Posts: 3,967 S.I. N.Y.
1MYTGTX
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OP
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Joined: Jan 2003
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S.I. N.Y.
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Thanks Brian, I dont know why this carb is giving me troubles. Made sure choke wasnt getting stuck etc....doesnt blow black smoke like its overly rich. Maybe I'm into the throttle more on the highway with this carb? Actually checked gas tank to make sure I wasnt leaking anything! Filled up before I left Carlisle and after 205 miles I'm on fumes!
1MYTGTX
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Re: Carter AVS mileage?
[Re: 1MYTGTX]
#1031085
07/12/11 10:31 PM
07/12/11 10:31 PM
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Joined: Jun 2005
Posts: 2,507 Royersford, PA
bschargerse
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master
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Royersford, PA
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I have a new Holley Street Dominator intake sitting in the box if you want to try it. Bolt that on with the Holley carb you have; I think it would be perfect for that Engle cam. More HP and torque than the old CH4B, and a nice low profile. I know you were going for the stock look though. If you want to try it, I'll ship it to you.
Brian - 1971 Dodge Challenger "The Dodge, which was practically stock, just left the Mustang like you wouldn't believe."
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Re: Carter AVS mileage?
[Re: 1MYTGTX]
#1031086
07/12/11 10:42 PM
07/12/11 10:42 PM
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Joined: Nov 2009
Posts: 2,275 Desert Tracker
HYPER8oSoNic
top fuel
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top fuel
Joined: Nov 2009
Posts: 2,275
Desert Tracker
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Quote:
Thanks Brian, I dont know why this carb is giving me troubles. Made sure choke wasnt getting stuck etc....doesnt blow black smoke like its overly rich. Maybe I'm into the throttle more on the highway with this carb? Actually checked gas tank to make sure I wasnt leaking anything! Filled up before I left Carlisle and after 205 miles I'm on fumes!
with Dogdays point, it is a GOOD carb for performance/economy. First, you need a history of the carb and what it came off of. The jetting could be the problem, if it's wrong for the size motor you have. Air door and basic settings, also could be wrong for your motor too! Holleys' are good performers too, but they are also user-friendly. The belief is they're more so than Carter's. Contrary to POPULAR belief, AVS's, AFB's and TQ's are relatively easier! If you are patient and have the info at hand, they CAN be set up RIGHT! Also, recheck your ignition timing thoroughly, again for good measure!!
"Stupidity is Ignorance on Steroids" "Yeah, it's hopped to over 160" (quote by Kowalski in the movie Vanishing Point 1970 - Cupid Productions)
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Re: Carter AVS mileage?
[Re: 1MYTGTX]
#1031088
07/12/11 11:51 PM
07/12/11 11:51 PM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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Nothing you ain't prob already thought of (& tried) but I'd do the basics: float level/vac leak/jetting/accel pump (for the hesitation). I'm assuming you are on ported vac. It was good b 4 & no ch ex for the restored AVS? OE avs's are emission carbs & there was the constantly changing stringent emission std's that were put on Ma (& the others) back in the late 60's early 70's but they can run like a scalded cat. There's a serious prob somewhere that is making it hesitate and that may b something other than a garden variety weak AP shot (I'm sure you've checked) & if so it is screwing up your AF ratio & killing the mileage. Holler when you find something EDIT I'm assuming the springs are keeping it on the "cruise" step(s) at the vac level you are maintaining at 3100 rpm
Last edited by RapidRobert; 07/12/11 11:54 PM.
live every 24 hour block of time like it's your last day on earth
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Re: Carter AVS mileage?
[Re: 1MYTGTX]
#1031092
07/13/11 09:55 PM
07/13/11 09:55 PM
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Joined: Feb 2003
Posts: 10,208 Someplace you aren't
SomeCarGuy
I Live Here
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I Live Here
Joined: Feb 2003
Posts: 10,208
Someplace you aren't
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You've got an issue there someplace. I always get good mileage with the AVS.
Make sure the rods are moving freely and aren't off track. Vac leaks, etc.
Something is wrong if you got 5 MPG w/ no other changes.
I want my fair share
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