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Re: 68 Charger cruise stumble - AVS carb question
[Re: 70mopes]
#2131275
08/12/16 05:17 PM
08/12/16 05:17 PM
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Joined: Jan 2003
Posts: 25,801
Rio Linda, CA
John_Kunkel
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,801
Rio Linda, CA
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A friend used to work at a local dealer, he specialized in tuneup/driveability. A lot of stock AVS's would have a lean surge at light throttle, his fix was to drill out the idle feed tube in the primary venturi cluster (this is the smaller of the two brass tubes that extend into the carb body).
The hole in the tube is very small, takes a miniature drill set to enlarge the opening a couple of drill sizes. Worked for me.
Another thing to check is the fit of the primary throttle shafts in the main body, simply wiggling the throttle lever around can cause the idle speed to change noticeably if the shaft is loose and causing a vacuum leak around the shaft....also causes a lean surge.
The INTERNET, the MISinformation superhighway
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Re: 68 Charger cruise stumble - AVS carb question
[Re: 70mopes]
#2133456
08/15/16 12:52 PM
08/15/16 12:52 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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pull the vac adv can hose & plug it & retry it
live every 24 hour block of time like it's your last day on earth
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Re: 68 Charger cruise stumble - AVS carb question
[Re: 70mopes]
#2133595
08/15/16 03:50 PM
08/15/16 03:50 PM
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Joined: Apr 2007
Posts: 2,327
Glendale, AZ
69L78Nova
Banned. Forever.
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Banned. Forever.
Joined: Apr 2007
Posts: 2,327
Glendale, AZ
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Have you even bothered to check the operation of the hot idle compensator valve like I suggested earlier?
1969 Nova
454/M21/3.31
Mild mid-11 second weekend cruiser
1994 F150 XLT Super Cab 2WD
5.0/4R70W/3.55
(Daily driver)
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Re: 68 Charger cruise stumble - AVS carb question
[Re: 70mopes]
#2134350
08/16/16 02:17 PM
08/16/16 02:17 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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with the can capped making it better you might check Rotor Phasing (my baby) and also total timing at the RPM where the problem is. yes the center heat riser openings ain't an intake port as you know but if the intake is warped enough or the gasket is bad it could be pulling a vac leak in at that point which it definitely sounds like it is doing, just make sure that the spray did not get pulled into the nearby carb airhorn or carb base & give a false symptom. not likely but pulling the intake is work & it never hurts to keep Mr Murphy at bay. I use a piece of cardboard to keep things isolated when testing. yes pull the intake & go from there
live every 24 hour block of time like it's your last day on earth
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Re: 68 Charger cruise stumble - AVS carb question
[Re: 70mopes]
#2134376
08/16/16 02:44 PM
08/16/16 02:44 PM
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Joined: Jun 2008
Posts: 3,916
usa
lewtot184
master
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master
Joined: Jun 2008
Posts: 3,916
usa
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Great tips fellas. Thanks.
I had the AVS apart yesterday, before reaching out on moparts. I cleaned up the pistons but not the bores in the carb. The metering rod on the passenger side was worn bad and the spring holding it was out of position and off the rod. I used a set of rods out of a 4429S. I also adjusted the floats to parallel with the top to increase the amount of fuel in the bowls. Overall that whole process seemed to richen the whole shebang up ... which is what I would expect. I adjusted the secondary air horn since I was getting a bog and smoke when matting the pedal.
The air/mixture screws are adjusted very far out. More than they should be in my opinion. When screwed all the way in and adjusted 1 1/2 turns out, the engine won't even start. I figured adjusting the float level and cleaning the emulsification tubes etc, along with fixing the needle/piston would make things better. If anything I am a bit worse with the same hunting problem and now and enrichment problem when throttling up.
I need to mention also that this is an original carb that has the single air bleed in the center top but now also has the two mixture screws in the bottom as well. Also, The emulsification tubes in the carb have only 4 small holes each. That indicates to me that the engine should be pulling a solid fuel mix to the idle circuit slots/holes. I am confused as to why it takes so much outward adjustment to get it to idle right.
I will follow up on the tips provided. any other insight would be appreciated.
backing the mixture screws out a lot with no big differences in idle quality indicates the idle jets are too small. they will need to be opened to at least .035". the 4618s avs i run works best with .037" idle jets. stock for an auto trans car is .031" and .035" for a 4spd.
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Re: 68 Charger cruise stumble - AVS carb question
[Re: 70mopes]
#2134528
08/16/16 06:37 PM
08/16/16 06:37 PM
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Joined: Jan 2003
Posts: 14,499
So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,499
So. Burlington, Vt.
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Plenty of good carb tuning tips in this thread, so I won't offer anything about that, but I will add that when I mill the intake side of those nearly 50 year old heads and intake manifolds......... They are always far from being flat.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
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