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OEM Carter AVS tuning issue #375674 07/14/09 10:41 PM 07/14/09 10:41 PM
Joined: Feb 2003 Posts: 10,211 Someplace you aren't S SomeCarGuy OP I Live Here
SomeCarGuy OP I Live Here S Joined: Feb 2003 Posts: 10,211 Someplace you aren't	I found a new Eddy AVS for sale but decided to try a 71 440 AVS on my 383 first since it was on the shelf. It replaced the hated Eddy 750 AFB. I had the AFB running OK but I think the AVS will be better. I rebuilt the AVS I have this afternoon. It runs OK but is rich(more on that in a minute) and the real problem is that after it gets reved to about 3K, it idles about 1100 RPM. Curb idle holds about 750 where I want it, returns after blipping the throttle lightly. It only has one port for the vac advance so I ASSUME that it is ported. The AFB idled fine after a rev fest. Timing is 10/34. The engine is a stock 70 383 HP with a HSD intake and headers. Good chain. Thr rich issue at idle maybe caused by the idle screws not screwing in the same since I had to tap one that was stripped. I noticed they aren't the same but they are all I have at the moment. That shouldn't matter on the idle speed after reving. What might do something weird is the rods. I have a 630 AVS that I had to one from since this carb had a BENT rod. The 630 even had a mismatched set so I ended up with one 575 rod and one 572 rod. Could that be a factor in the hanging idle? I want my fair share

Re: OEM Carter AVS tuning issue [Re: SomeCarGuy] #375675 07/14/09 11:05 PM 07/14/09 11:05 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: It only has one port for the vac advance so I ASSUME that it is ported. The 630 even had a mismatched set Could that be a factor in the hanging idle? (yes ported) (2) no. check that it's not catching on the fast idle cam steps. that the throttle blades ain't hanging up in the bores and that you have a strong enough return spring. live every 24 hour block of time like it's your last day on earth

Re: OEM Carter AVS tuning issue [Re: RapidRobert] #375676 07/14/09 11:12 PM 07/14/09 11:12 PM
Joined: Feb 2003 Posts: 10,211 Someplace you aren't S SomeCarGuy OP I Live Here
SomeCarGuy OP I Live Here S Joined: Feb 2003 Posts: 10,211 Someplace you aren't	I looked at the fast idle and it isn't hitting. I have the choke wired open. Plenty of return spring. Two actually. THe throttle bores sticking could be a winner.

Re: OEM Carter AVS tuning issue [Re: SomeCarGuy] #375677 07/14/09 11:15 PM 07/14/09 11:15 PM
Joined: Feb 2003 Posts: 10,211 Someplace you aren't S SomeCarGuy OP I Live Here
SomeCarGuy OP I Live Here S Joined: Feb 2003 Posts: 10,211 Someplace you aren't	I'll have to get a vaccum gauge to get the idle mix correct. It has kind of a rough idle compared to the AFB. Any good ideas on where to get some matched rods? I guess I could go to the two step rods but I bet the 3 step will be worth the effort and will be fine if both are matched.

Re: OEM Carter AVS tuning issue [Re: SomeCarGuy] #375678 07/14/09 11:21 PM 07/14/09 11:21 PM
Joined: Feb 2003 Posts: 10,211 Someplace you aren't S SomeCarGuy OP I Live Here
SomeCarGuy OP I Live Here S Joined: Feb 2003 Posts: 10,211 Someplace you aren't	I found this interesting on a search- "Check to see if you have the "hot idle compensator valve" on your carb., its basically a bi-metal strip that when open, allows a passage to the manifold vacuum. Most hot-rodders (in my day), fashioned a block off plate to eliminate this really crude emissions device. I remember that being a common problem." Could this be giving me trouble? Either for the high idle on return or the general rough idle? I know I have issues that will cause the idle to be rough currently but is this something to invesigate? I know a compensator isn't in there.

Re: OEM Carter AVS tuning issue [Re: SomeCarGuy] #375679 07/14/09 11:32 PM 07/14/09 11:32 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	AVS strip kits are extremely rare nowadays & I think I just saw a parts AVS for cheap in one of the parts for sale sections which'd get you some rods. they might not be 100% correct but they would be matched but with that being said the AVS was an emission carb of that era of gov't regs that were starting to get severe(& the carb tech had not caught up and the AVS with its 3 step rods w the intermediate step are inferior to the earlier AFB(w 2 step rods)for performance so I would get an eddy strip kit & as you know the flat covers. I would take out the idle screws & straighten that out and anything else that's off especially w the rods getting bent by a prior owner live every 24 hour block of time like it's your last day on earth

Re: OEM Carter AVS tuning issue [Re: RapidRobert] #375680 07/14/09 11:42 PM 07/14/09 11:42 PM
Joined: Feb 2003 Posts: 10,211 Someplace you aren't S SomeCarGuy OP I Live Here
SomeCarGuy OP I Live Here S Joined: Feb 2003 Posts: 10,211 Someplace you aren't	I thought that the 3 step rods were better for getting a precise mix since it has another stage? So I would be better serving to run the AFB parts then and not fool with getting AVS rods?

Re: OEM Carter AVS tuning issue [Re: SomeCarGuy] #375681 07/14/09 11:46 PM 07/14/09 11:46 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	Before you do anything else pull the throttle cable off the carb and try it with just the return spring on.

Re: OEM Carter AVS tuning issue [Re: SomeCarGuy] #375682 07/14/09 11:46 PM 07/14/09 11:46 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: I know a compensator isn't in there. It has the compensator recess but no bimetallic strip to open the air bleed so it is open all the time? If so I'd epoxy it(the extra air bleed hole) shut. live every 24 hour block of time like it's your last day on earth

Re: OEM Carter AVS tuning issue [Re: RapidRobert] #375683 07/14/09 11:50 PM 07/14/09 11:50 PM
Joined: Feb 2003 Posts: 10,211 Someplace you aren't S SomeCarGuy OP I Live Here
SomeCarGuy OP I Live Here S Joined: Feb 2003 Posts: 10,211 Someplace you aren't	I'll go out now and pull the cable. It was in the same spot as the old carb needed it so??? But worth eliminating. I honestly didn't pay any attention to the compensator area other than it didn't have one. If it were bleeding fully all the time I would think I wouldn't have such a rich idle. Or would that cause the high idle right there?

Re: OEM Carter AVS tuning issue [Re: SomeCarGuy] #375684 07/15/09 12:03 AM 07/15/09 12:03 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	Not sure but it is a controlled vac leak(which can raise the idle speed)(though a small one) but I think other issues going on especially with you being able to blip the throttle & it straightens out and did you say it was part time which(in this case) point to a mechanical hangup. live every 24 hour block of time like it's your last day on earth

Re: OEM Carter AVS tuning issue [Re: RapidRobert] #375685 07/15/09 12:12 AM 07/15/09 12:12 AM
Joined: Feb 2003 Posts: 10,211 Someplace you aren't S SomeCarGuy OP I Live Here
SomeCarGuy OP I Live Here S Joined: Feb 2003 Posts: 10,211 Someplace you aren't	Quote: Not sure but it is a controlled vac leak(which can raise the idle speed)(though a small one) but I think other issues going on especially with you being able to blip the throttle & it straightens out and did you say it was part time which(in this case) point to a mechanical hangup. It ran fine in the garage, so i took it down the road. Noticed the hangin idle and came home. Tried to pinpoint and figured out it was around 3K that it caused it not to idle right. A few blips and it clears.

Re: OEM Carter AVS tuning issue [Re: SomeCarGuy] #375686 07/15/09 12:18 AM 07/15/09 12:18 AM
Joined: Feb 2003 Posts: 10,211 Someplace you aren't S SomeCarGuy OP I Live Here
SomeCarGuy OP I Live Here S Joined: Feb 2003 Posts: 10,211 Someplace you aren't	I went out to take the cable off and test and thought better about waking up the world. So I looked around for my AFB stip kit to see what rods and jets I still had. Getting discouraged, I made a discovery that is hard to believe. Hidden in a box on the top shelf was ANOTHER 71 440 AVS! Praise the lord! Not only is it the same 4966 carb, it appear to have never been touched- ever. It still has the blue carb tag on it, still had the factory air cleaner stud. Dirt and grime appear consistant all around. I sprayed the idle screws down and carefully worked them back and forth- move pretty well. They are dead even sticking through the bore. I pulled a rod and it is a 572 like the other carb. SO I guess tommorrow I will put the new accel pump in it and see what we get. One other note- the hot idle compensator is still in this one. I'll give it a whirl as is before I go and lead over anything.

Re: OEM Carter AVS tuning issue [Re: SomeCarGuy] #375687 07/15/09 08:56 AM 07/15/09 08:56 AM
Joined: Jan 2003 Posts: 75,012 U.S.S.A. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,012 U.S.S.A.	Quote: I went out to take the cable off and test and thought better about waking up the world. So I looked around for my AFB stip kit to see what rods and jets I still had. Getting discouraged, I made a discovery that is hard to believe. Hidden in a box on the top shelf was ANOTHER 71 440 AVS! Praise the lord! Not only is it the same 4966 carb, it appear to have never been touched- ever. It still has the blue carb tag on it, still had the factory air cleaner stud. Dirt and grime appear consistant all around. I sprayed the idle screws down and carefully worked them back and forth- move pretty well. They are dead even sticking through the bore. I pulled a rod and it is a 572 like the other carb. SO I guess tommorrow I will put the new accel pump in it and see what we get. One other note- the hot idle compensator is still in this one. I'll give it a whirl as is before I go and lead over anything. FYI the 4966 is a 650 carb , not a 750 , it's application is 71 non HP 440 and it will be RICH on your 383 since it is calibrated on the rich side for the 440 it came off of. The factory calibration was a compromise to save on warranty issues.

Re: OEM Carter AVS tuning issue [Re: JohnRR] #375688 07/15/09 10:45 AM 07/15/09 10:45 AM
Joined: Feb 2003 Posts: 10,211 Someplace you aren't S SomeCarGuy OP I Live Here
SomeCarGuy OP I Live Here S Joined: Feb 2003 Posts: 10,211 Someplace you aren't	That's right, I do remember looking that up awhile back.

Re: OEM Carter AVS tuning issue [Re: SomeCarGuy] #375689 07/15/09 11:09 AM 07/15/09 11:09 AM
Joined: Jan 2003 Posts: 75,012 U.S.S.A. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,012 U.S.S.A.	Quote: That's right, I do remember looking that up awhile back. I installed that same carb on a 330HP 383 and it did run very well for the few times I did drive the car .

Re: OEM Carter AVS tuning issue [Re: JohnRR] #375690 07/15/09 11:11 AM 07/15/09 11:11 AM
Joined: Feb 2003 Posts: 10,211 Someplace you aren't S SomeCarGuy OP I Live Here
SomeCarGuy OP I Live Here S Joined: Feb 2003 Posts: 10,211 Someplace you aren't	I bet it will do what I want- smooth performance all around. THe 750 Eddy just doesn't do that. I noticed the throttle response seemed better with the cobbled up avs last night.

Re: OEM Carter AVS tuning issue [Re: SomeCarGuy] #375691 07/15/09 09:36 PM 07/15/09 09:36 PM
Joined: Feb 2003 Posts: 10,211 Someplace you aren't S SomeCarGuy OP I Live Here
SomeCarGuy OP I Live Here S Joined: Feb 2003 Posts: 10,211 Someplace you aren't	OK, after much fiddling today, I got the untouched carb on there and working. It had a few issues but i worked them out. Right now I have two problems with it. One is the idle seems erratic. I smoothed that out with adjusting the mixture but it still seems rough compared to the Eddy 750 AFB. Also, I feel a slight lean surge at part throttle. I saw a comment online while searching today that a drop base air cleaner will cause the carb to idle strange as it outs the lid too close to the idle bleeds. Might this be my issue? I could drive a little with it off and check I suppose. So far it has been less smooth than the Eddy was and that was why I wanted to change it out

Re: OEM Carter AVS tuning issue [Re: SomeCarGuy] #375692 07/15/09 10:59 PM 07/15/09 10:59 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: One is the idle seems erratic. Also, I feel a slight lean surge at part throttle. that a drop base air cleaner will cause the carb to idle strange as it outs the lid too close to the idle bleeds. Might this be my issue? I could drive a little with it off and check I suppose. (1) you might take out the idle mixture screws(count the turns) & blast a 1 second shot of starting fluid into each hole then reinstall the screws. (2) I was going to suggest a rod w a thinner "cruise" step then I remembered you have no other rods/jets to play with (3) with the lid off you'd find out in several seconds. Good luck on it. live every 24 hour block of time like it's your last day on earth

Re: OEM Carter AVS tuning issue [Re: RapidRobert] #375693 07/15/09 11:10 PM 07/15/09 11:10 PM
Joined: Feb 2003 Posts: 10,211 Someplace you aren't S SomeCarGuy OP I Live Here
SomeCarGuy OP I Live Here S Joined: Feb 2003 Posts: 10,211 Someplace you aren't	I went for a longer cruise to see if maybe it would clean up a bit. I noticed that there seems to be a lot of popping in the exhaust now. Not loud but the engine definetly isn't happy. Lots of popping sounds on decel. Would seem to be lots of unburned fuel igniting in there. That seems out of wack as it is surging. I was thinking a K&N might lean it out but then that wouldn't help a surge. Maybe dirt is in something??? The air valve isn't spot on as it doesn't seem to be opening up quick enough. Oddly, I punched it from a 25 MPH roll in second and it bogged like they flew open too quick. Maybe a pump shot issue? I had to take it back apart and I cleaned the accelerator pump circuit and nothing came out. I decided to use the shooter from the other 4966 and it worked. Before i wasn't getting any shot unless i went half throttle or more. I checked the setting and it is spot on per the rebuild kit papers. I could change the rod hole and get a bigger shot by going to the top hole from the middle hole.

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