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Carter AVS tuning problem #1454753 06/18/13 10:51 AM 06/18/13 10:51 AM
Joined: Jan 2003 Posts: 7,843 Spring Mount, PA MOPAULY OP master
MOPAULY OP master Joined: Jan 2003 Posts: 7,843 Spring Mount, PA	I just rebuilt the AVS on my 68 383 - after adjusting timing a bit it seems to work really well with one exception - the idle mixture screw seems to have no effect; even fully seated the engine idles fine. This is a 68 carb so there is only a single screw; I'm not a fan of these carbs to begin with as they've always been troublesome for me as opposed to Holley's. Any idea what the cause of the issue is? floats were set per the included instructions, although I may take the top off and check again.

Re: Carter AVS tuning problem [Re: MOPAULY] #1454754 06/18/13 11:08 AM 06/18/13 11:08 AM
Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska	I'd leave the top on as the floats are OK. Wait for someone who knows that system live every 24 hour block of time like it's your last day on earth

Re: Carter AVS tuning problem [Re: RapidRobert] #1454755 06/18/13 11:16 AM 06/18/13 11:16 AM
Joined: Jan 2003 Posts: 7,843 Spring Mount, PA MOPAULY OP master
MOPAULY OP master Joined: Jan 2003 Posts: 7,843 Spring Mount, PA	yeah based on some tshooting I just read floats don't seem to be related to this. It's odd, if you turn the screw out it will increase in idle, but even fully seated it idles fine and still smells rich at the tailpipes.

Re: Carter AVS tuning problem [Re: MOPAULY] #1454756 06/18/13 11:18 AM 06/18/13 11:18 AM
Joined: Mar 2003 Posts: 18,678 Fresno, CA Jim_Lusk I Live Here
Jim_Lusk I Live Here Joined: Mar 2003 Posts: 18,678 Fresno, CA	The single screw is an air bleed. There are two mixture screws under lead plugs and probably won't move if you get the plugs out (at least that's been my experience). The original carb for my 68 340 had the same problem that I never fixed except for replacing it with a 69 carb...

Re: Carter AVS tuning problem [Re: Jim_Lusk] #1454757 06/18/13 11:32 AM 06/18/13 11:32 AM
Joined: Jan 2003 Posts: 7,843 Spring Mount, PA MOPAULY OP master
MOPAULY OP master Joined: Jan 2003 Posts: 7,843 Spring Mount, PA	I did read up on that a bit, I guess part of an emissions control they were trying to do. I wonder if it's worth messing with beyond this point or just replacing it with something newer. I plan to drive the car quite a bit once it's road ready and the rich idle is pretty obnoxious.

Re: Carter AVS tuning problem [Re: MOPAULY] #1454758 06/18/13 12:12 PM 06/18/13 12:12 PM
Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska	That is surprising that it is way rich at idle since it was an emissions carb. If the main metering is lean you can convert to the Eddy 2 step rods/shorter pri jets. go a couple of tho richer than whats in there now for a start at least on the "cruise" step & fill the domed metering rod caps with JB weld then cover it with scotch tape then turn it over so the JB will settle flat/even on the tape & let it setup like that for several days live every 24 hour block of time like it's your last day on earth

Re: Carter AVS tuning problem [Re: MOPAULY] #1454759 06/18/13 12:32 PM 06/18/13 12:32 PM
Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio Challenger 1 Too Many Posts
Challenger 1 Too Many Posts Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio	Quote: I did read up on that a bit, I guess part of an emissions control they were trying to do. I wonder if it's worth messing with beyond this point or just replacing it with something newer. I plan to drive the car quite a bit once it's road ready and the rich idle is pretty obnoxious. This reminds me of a recent tuneup I gave my car. 600 1405 edlebrock carb on a 340 with a 474 cam. I got the vacuum gauge and timing light out. I didn't change my timing, 24 initial and 35 total plus vacuum advance. What I did windup doing is open my idle mixture screws a little and that helped my idle. But also what I think it did was got rid of some of the smell from my exhaust. I have always thought rich idle caused the smell, but I'm now thinking it was a too lean of a idle causing some of the smell? At least in my case.

Re: Carter AVS tuning problem [Re: Challenger 1] #1454760 06/18/13 12:37 PM 06/18/13 12:37 PM
Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska	Quote: What I did windup doing is open my idle mixture screws a little and that helped my idle. But also what I think it did was got rid of some of the smell from my exhaust. I have always thought rich idle caused the smell, but I'm now thinking it was a too lean of a idle causing some of the smell? At least in my case. Very good point as a lean misfire could certainly let unburned mixture out the exhaust live every 24 hour block of time like it's your last day on earth

Re: Carter AVS tuning problem [Re: Challenger 1] #1454761 06/18/13 12:41 PM 06/18/13 12:41 PM
Joined: Feb 2003 Posts: 10,203 Someplace you aren't S SomeCarGuy I Live Here
SomeCarGuy I Live Here S Joined: Feb 2003 Posts: 10,203 Someplace you aren't	Can you get the plugs out and tap it for regular AVS mixture screws? I've never had an AVS with the plugs. Mine always had screws and I could get the idle set right where I wanted it. I think the only ones I have had were 69-71 model carbs. I want my fair share

Re: Carter AVS tuning problem [Re: SomeCarGuy] #1454762 06/18/13 02:09 PM 06/18/13 02:09 PM
Joined: Mar 2003 Posts: 18,678 Fresno, CA Jim_Lusk I Live Here
Jim_Lusk I Live Here Joined: Mar 2003 Posts: 18,678 Fresno, CA	If you have that screw all the way in (counter clockwise) that is the richest setting. They have left hand threads so that leaner and richer are the same rotation as a fuel screw.

Re: Carter AVS tuning problem [Re: Jim_Lusk] #1454763 06/18/13 03:01 PM 06/18/13 03:01 PM
Joined: Jan 2003 Posts: 7,843 Spring Mount, PA MOPAULY OP master
MOPAULY OP master Joined: Jan 2003 Posts: 7,843 Spring Mount, PA	Quote: If you have that screw all the way in (counter clockwise) that is the richest setting. They have left hand threads so that leaner and richer are the same rotation as a fuel screw. The manual tells me the opposite? fully seated is lean? right now it's fully seated, rpms go up if you turn clockwise and back it out.

Re: Carter AVS tuning problem [Re: Jim_Lusk] #1454764 06/18/13 04:04 PM 06/18/13 04:04 PM
Joined: Jan 2003 Posts: 7,843 Spring Mount, PA MOPAULY OP master
MOPAULY OP master Joined: Jan 2003 Posts: 7,843 Spring Mount, PA	Wait, are you saying that full in is all fuel and no air? I may be misunderstanding the purpose of this adjustment...if that is the case, this thread answers it and I've been adjusting it backwards: https://board.moparts.org/ubbthreads/showflat.php?Number=7637012&page=0 to that point good thing I didn't have the impact on full hammer when I took the driver side wheels off as they are reverse thread, I didn't realize there were still doing that in '68. Last edited by MOPAULY; 06/18/13 04:06 PM.

Re: Carter AVS tuning problem [Re: MOPAULY] #1454765 06/18/13 04:24 PM 06/18/13 04:24 PM
Joined: Mar 2003 Posts: 18,678 Fresno, CA Jim_Lusk I Live Here
Jim_Lusk I Live Here Joined: Mar 2003 Posts: 18,678 Fresno, CA	Yes, full in is no air bleed. Just like the fuel screws, clockwise leans, counter clockwise richens. That's why it has left-hand threads.

Re: Carter AVS tuning problem [Re: Jim_Lusk] #1454766 06/18/13 04:33 PM 06/18/13 04:33 PM
Joined: Jan 2003 Posts: 7,843 Spring Mount, PA MOPAULY OP master
MOPAULY OP master Joined: Jan 2003 Posts: 7,843 Spring Mount, PA	that explains it - she's still a stinky [Edited by Moparts - Family Friendly Site - Keep it clean] with the screw turned out but i'll need to check plugs and so forth. I'm guessing I should back the screw out until I hit maximum vacuum?

Re: Carter AVS tuning problem [Re: MOPAULY] #1454767 06/18/13 04:43 PM 06/18/13 04:43 PM
Joined: Feb 2003 Posts: 10,203 Someplace you aren't S SomeCarGuy I Live Here
SomeCarGuy I Live Here S Joined: Feb 2003 Posts: 10,203 Someplace you aren't	Are the metering rods working up and down as they should. I've seen the rods get bent and they are not going into the jet. You can work them up and down to ensure the movement is clean.

Re: Carter AVS tuning problem [Re: Jim_Lusk] #1454768 06/18/13 04:55 PM 06/18/13 04:55 PM
Joined: Jan 2003 Posts: 7,843 Spring Mount, PA MOPAULY OP master
MOPAULY OP master Joined: Jan 2003 Posts: 7,843 Spring Mount, PA	so after more reading it seems like these carbs can richen up if left idling to long while hot. I guess I'll run with it for now as I need to spend $$ on other things, a new holley can come later on.

Re: Carter AVS tuning problem [Re: MOPAULY] #1454769 06/18/13 05:22 PM 06/18/13 05:22 PM
Joined: Feb 2003 Posts: 10,203 Someplace you aren't S SomeCarGuy I Live Here
SomeCarGuy I Live Here S Joined: Feb 2003 Posts: 10,203 Someplace you aren't	Some versions have an idle air bleed that sits near the butterflys in between them. Might see if it has the provision for it or if you could drill it out and add it. IIRC, it heats up and opens up sort of like a choke when at a certain temp, thereby giving you more air at idle. I may have one in an old junk carb.

Re: Carter AVS tuning problem [Re: SomeCarGuy] #1454770 06/18/13 07:16 PM 06/18/13 07:16 PM
Joined: Mar 2003 Posts: 18,678 Fresno, CA Jim_Lusk I Live Here
Jim_Lusk I Live Here Joined: Mar 2003 Posts: 18,678 Fresno, CA	I believe what you are describing is a backfire device, but I could be mistaken...

Re: Carter AVS tuning problem [Re: Jim_Lusk] #1454771 06/18/13 09:17 PM 06/18/13 09:17 PM
Joined: Jan 2003 Posts: 9,436 Blair County,PA 62maxwgn master
62maxwgn master Joined: Jan 2003 Posts: 9,436 Blair County,PA	Quote: I believe what you are describing is a backfire device, but I could be mistaken... Actually it is a hot idle compensator and not on a 68 carb,also,to SCG,there are mixture screws behind the plugs.Here is one with the plugs removed and mixture screws installed. 7747420-P2060573.JPG (284 downloads)

Re: Carter AVS tuning problem [Re: 62maxwgn] #1454772 06/19/13 01:19 PM 06/19/13 01:19 PM
Joined: Jan 2003 Posts: 7,843 Spring Mount, PA MOPAULY OP master
MOPAULY OP master Joined: Jan 2003 Posts: 7,843 Spring Mount, PA	Quote: Quote: I believe what you are describing is a backfire device, but I could be mistaken... Actually it is a hot idle compensator and not on a 68 carb,also,to SCG,there are mixture screws behind the plugs.Here is one with the plugs removed and mixture screws installed. any real benefit to this? It will eventually get replaced with a holley so I don't know if I'd bother with it. Plus it takes away from the resto factor should I get to that point.

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