Swapping Your Imperial's Carburetor From A Holley To A Carter


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From Pete:

Yesterday I decided to forge ahead with the Holley 4160-to-Carter AVS swap on my 70 LeBaron. This despite knowing that the Holley choke thermostat probably wouldn't fit the Carter and I hadn't bent a fuel line to fit the AVS. Removing the Holley and installing the Carter took about 10 minutes. Throttle/cruise linkage connections matched and so did PCV and distributor vacuum hoses. As expected, the Holley choke thermostat does not work with the Carter and cannot even be connected. I communicated with someone here or on the MML that has a 70 Hurst and he indicated that a Carter BP224 is the part I need. The 3 local parts houses I contacted all said that the number is useless to them; this surprised me. Worse yet, when I gave the application I was looking for they all said that the part was not available. I'll call NAPA next, but thought that I would ask this group for advice. I wanted to get the car running so I left the Holley fuel line in place and ran some 3/8" hose from it to the carb fuel inlet. I wired the AVS choke partially closed, drained fuel from the Holley into the intake and hit the "go" switch. The engine started and seemed to run well. I let it warm up for awhile and checked for leaks -- none. The temp fuel line hookup seemed okay for a short test drive so I installed the air cleaner and went for a short spin. In short, the car seems to idle, accelerate, and cruise exceptionally well. It will take awhile for me to get used to not braking with my left foot as I approach a stop sign because that's what was necessary with the Holley to keep the engine from dying. My gawd! I may be able to actually drive this car once in awhile again. Of course I got smacked by the "two steps forward, one step back" rule... After parking the car and standing there to admire it for a bit, I smelled raw gas. Then I saw the drip from below the passenger's side rear door. Great. Looks like the metal fuel line along the rocker has a pin hole. That should be a lot of fun to fix.

Tip from Dick:

Both the Holley 4160 and the Carter AVS carburetors were used in the 1968 Imperials. If you have a Carter, count yourself lucky. While some prefer the Holley for "ease of tuning", most agree that the Carters were just about trouble free, which no one ever claimed for a Holley 4160.

From Brian:

This seems to be the biggest anti-holley list in the world. I personally like the holleys. Don't get me wrong, the Carters are great carbs. If Holleys are such a bad carburetor, why is it that Holleys are the preferred carb for high performance or racing? I have holleys on both my Imp and my 300 and have had no problem. The one on the Imp needs rebuilt, but has not been touched for 6 years. The 300 has a crusty fuel tank and plugs up a filter in about a week(tank full). It has been on there for two years and still runs great. Like I said, I like holleys and see nothing wrong with them.


From Elijah:

Probably because Holley carbs offer more options for performance tweaking. And since racers generally tune the car before each run, this is an advantage.

An Imperial, however, is a dignified, luxury automobile. The owner of an Imperial should not be expected to pop the hood and fiddle with the carburetor each time he or she plans to drive the car.

The Carter offers comparable performance, but with MUCH greater dependability. An AFB is probably the closest thing to a "bullet-proof" carburetor ever made, and the AVS is a close second. AND even the novice can generally get good results from rebuilding an AFB or AVS (which can't be said of either the Holley or the Carter ThermoQuad).

From Roy:

Because a race is only one day! I don't know what it is about Holleys that makes them so troublesome, new gasoline formulation that causes leaks, excessive drying out due to heat or storage, bad float design, etc., etc., but they just don't work well long term, without at the least fiddeling with them.

When I got my Imperial it had a Holley that needed constant fiddeling, so I fianlly rebuilt it and did a major tune up, and the car ran great, would idle down to almost nothing! Shortly thereafter made a ten hour roundtrip to Lowell Howe for some parts, getting 14 plus MPG, then parked the car for about two months while it was being worked on. The car would never run with the Holley again, wouldn't even start, and leaked like a sieve! Thats when it got its Carter, that hasn't been touched since I initially rebuilt it and it was put on. The car will start after three days or three months of being parked! I have never been able to get it to idle down as low as with the Holley or get as good gas mileage, but the trade off has been worth it, IMHO.

From Kerry:

My neighbor, a self proclaimed Chevy god and holley guru, says the kind on our cars, ie without dual fuel lines to both ends, are crap. I'd agree based on the way it runs. He says they aren't even worth rebuilding and he's offered to build any of my carbs.

From Michael:

I have to add my two cents to this conversation about Holleys vs. Carters: I like them BOTH ; each has an advantage over the other. I presently own a 1969 LeBaron and a 1967 Crown and have owned a 1972 New Yorker Brougham off which I put on a 69 model year Holley. I had no problems with them at all, and in fact we went on a 1,100 mile trip with the 67 to the Adirondacks , part of Canada(what a time getting BACK IN to the USA!!!) and the Catskills before heading back to the Boston, Massachusetts area back in mid April, and the car STILL purrs like a kitten and would give any so-called "Muscle " car a run for the money( if I HAD any!). My point is that you or your mechanic HAVE to know what you are doing when rebuilding ANY carburetor, especially Holleys. Case in point: there is a particular gasket that goes between the Primary Metering Block and the carb. housing.This HAS to be the proper gasket for that particular Model carb., and it only goes on ONE way. I found out the hard way when I put it on backwards and experienced the same problems with rough to NO idle. I dismantled it and reversed the gasket, and the rest is history. Also, the manifold gasket between the carburetor and intake should be replaced with a slightly thicker Fiberous style which resists heat better than the thinner hard gasket. Also all bolts such as the carb to manifold and the Fuel Bowl screws should be retweeked after about 100 hors of usage as the Hot to Cold to Hot , etc. cycle and vibrations from the Engine itself can relax the Torque of the bolts, causing AIR to get in where it should not. You want the air to go down the throat of the carb., drawing the proper gas mixture through your idle circuit and venturis Not underneath the carb. or through the gaskets. I have gained a lot of experience working with Holleys over the years, and can offer further tips on them if anyone wants to know.

Question from Ed (1968):

I have decided that I have a leakage problem with my Holly Carb. It would appear that the Carter AVS swap would be the way to go. Where would I find one of these? In the repair section of the website it is noted that there may be difficulty connecting the choke thermostat to the Carter: Has there been any more experience with the swap and the choke thermostat?


From Rob:

You can't get an AVS new. Rather than deal with another old-used-rebuilt carb, I would suggest you go for a new Carter AFB or Edelbrock carb. The Edelbrock is based on the AFB. You can get a 750 or 625 cfm. I don't know which Imperials came with stock. I know that hp 440s came with 750 avs. Either should bolt right on, but you may need the linkage kit. Check out Summit or Jegs.

Correction from Pete:

Au contraire!

It has been reported on other lists that the AVS carb is back in production (be Edelbrock). I have yet to see which models, but others do report availability of this carb.

From Jim:

I once replaced a factory Holley on a 440 with an AVS and the links and levers on the side of the AVS got in the way of the choke link.

Follow-up question from Ed:

The Edelbrock site offered up the following options for the retrofit carburetor:

1407 Performer Series; Carburetor; 750cfm; Square-Flange; Manual Choke; w/o EGR; "Universal Fit"
1411 Performer Series; Carburetor; 750cfm; Square-Flange; Electric Choke; w/o EGR; "Universal Fit"

As I haven't seen any wires attached to the Holly, I'm guessing that the manual choke option is what I'm looking for.

Also offered were these items which I don't think I need but possibly may:

Carburetor Stud
Carburetor Throttle Kicker
Carburetor Throttle Lever Extension
Kickdown Linkage

Does this sound correct?

Reply from Steve:

I would stay away from the 1407/1411. 750cfm is too much carb for our engines. I bought one for my Imperial and was very unsatisfied with it. Top end was great, but low end performance was horrid. I ended up having a correct carb rebuilt for the car and selling the Edelbrock on ebay.

Reply from Kerry:

No No, you don't want manual choke. Trust me, manual chokes stink. You want the electric choke option and they offer one with Chrysler linkage. To hook up the electric choke, you just have to run a hot wire from a switched source like the ballast resistor. The choke stove in the manifold will no longer be necessary.

Reply from Rob:

I would definitely go for the electric choke. Manual choke would mean you have to run a cable for the manual choke through to the interior. An electric choke saves a lot of headaches and I think it eliminates some of the linkage problems of the stock ones. You may need some of the other items. I think they sell them as a kit to install in a Mopar.

Reply from Robin:

The only thing you should need is the air cleaner rod as the Holley one is too short. I just made one with some threaded rod 1/8". You will also have to make a different steel fuel line feeding the carb but that is easy. Have to flare one end and reuse the fitting from the Holley.

Follow-up from Dick:

The air cleaner hold down rod is 1/4-20 thread - you can buy "all thread" rod at the hardware store and cut it to length. Its diameter is 1/4 inch.

The choke hookup for the Holley may be different for that of the AVS or AFB - but if you buy the new carburetor, it will come with electric choke assist, which is better than the original, and very easy to connect - it simply goes to the "I" terminal of the ignition switch.

Question from John (1969):

I'm about to replace the carburetor on my '69 with a Carter 9636 & am wondering how anyone that has already done this overcame the problem of having a 5/16 fuel line & a 3/8 fitting on the carburetor? The instructions say you need to use a hose & not to try to remove the carburetor fitting to connect the existing metal fuel line, but offers no real advice on how to accomplish this. My first thought was just to use the 3/8 hose & tighten the clamp a little tighter at the fuel pump, but am having 2nd thoughts on that. Any suggestions would be appreciated.


From Paul:

You can get a fitting at the local auto parts store that will screw into one size and allow you to use the other size to hook up the line.

From Steven:

Go to the auto parts store and get an adapter fitting from 5/16 flare fitting to 3/8 inverted flare.

From Rob:

The PO put that carburetor on mine in place of the EFI. They have little step metal adapters you could use in place of the rubber line. As far as I'm concerned, the less rubber line the better anyway. Just enough to allow for the engine motion.

Question from Greg:

I installed the newly rebuild Carter 750cfm AFB carburetor on my '67 in place of the troublesome stock Holley. In the process of installing I used a gasket from the Holley rebuild kit to go between the new Carter carburetor and the manifold. Granted it was for a Holley, but it was brand new and appeared to mate perfectly to the Carter. Here's the problem; the car will not start. Beautiful weather has proven that the problem can't be the choke (pull off). The Carter currently does not have a pull off valve, but I worked the butterfly by hand during the starting process to no avail. Yes, I do need a source for a pull off valve and will check NAPA. Plenty of fuel getting to the carburetor, new lines, filters and fuel pump. Carburetor was tested on another vehicle prior to being sent to me and worked perfectly. All electrical components related to ignition have also been replaced (including starter relay). My only guess is that the Holley gasket must be cut differently that the Carter one would be, perhaps it is blocking a hole on the underside of the carburetor that should be open? Any suggestions?


From Roy:

If the Holley gasket matched the bores of the Carter without interfering with the butterflies, it should be fine.
It takes fuel, air, compression and ignition for an engine to run.

You may have some false confidence that the AFB "was tested on another vehicle prior to being sent to me and worked perfectly", barring that, you may have an issue with fuel or ignition. Unplug a plug wire and insert a spark plug and lay it on the exhaust manifold, hold it down with a stick so it has a good ground and have someone crank the engine, if you see a spark, you are good. Next is timing, did you mess with the distributor since the car last ran? Try disconnecting and plugging the vacuum line to the advance biscuit on the distributor, you may have it connected to the wrong vacuum port on the carburetor. Finally, disconnect the fuel line at the carburetor and crank the engine to make sure you are getting fuel all the way up there.

From Jim:

The engine may just be flooded. If you are sure you have spark and that its timed right, I'd let it sit a day or two so any excess fuel evaporates from the cylinders and the spark plugs while I troubleshoot the starter. Then I'd give it a quick shot of starting fluid and no choke. If a non-flooded engine won't at least try to fire on instant start, there is a problem besides the carb.

Question from Steve:

I found an AVS number 4966S languishing in the shop a couple of weeks ago.  Does anybody know what this carb is off of?  I want to replace the Holley on the '68 in the worst way before putting her on the road.

Reply from Pete:

The 4966S carb is off a 71 Imperial 440/335 (and probably other 71 440s as well).  I recently installed a 4966S on my 70 LeBaron to replace the problematic original Holley 4160.  All is now well.  I was a bit worried about air cleaner fit, but it was a match.   Throttle/cruise linkage also fit fine.

Problems I did encounter during the Holley to Carter swap:

1)  predictably, the fuel line from pump to carb is different.  I got a used line from Murray Park.

2) you will need a different choke thermostat for the Carter.  I had absolutely no luck buying a new one locally, and ended up getting a used one (again from Murray Park).

3) the Carter has a bowl vent fitting that leads to a crankcase breather on 71s.  You may want to plug this.  I didn't, and have had no problems to date.

4) the air cleaner stud on the Holley won't work with the carter.  I can't remember if it was too short or too long.  Buy a length of 1/4-20 threaded rod (or get a used part from, you guessed it, Murray Park!)

Kerry's experience:

Some of you might remember that I have been fighting a little drivability problem with my 73. I'm thinking about selling her and want it to be right before I do.

It has a new "rebuilt" thermoquad. At Anniston, I noticed it would 'cough' when it was cold off idle and seemed to have a flat spot at WOT at about 4000 (and up) RPM (top of first and second gear). Normally, I'd have never noticed it but when tuning, I tend to push harder than normal driving.

I messed with it for hours and got it some better but was not happy.

Elijah Scott told to throw the TQ away and buy a new Carter AFB. Turns out he was coming to Huntsville this weekend and he brought his Carter with him. This afternoon we swapped it out and it made an immediate difference once I replaced #2 spark plug wire that was knocked loose. So the problem was definitely in the carb.

We put the TQ back on and adjusted the main jets per the "old carb god" recommendations. Basically this was to press down the bar until and back the screw on the metal bar until there was no movement. Then turn it in 3 1/2 turns.

On the first test, I punched the gas, there was a slight bog then a HUGE punch. Elijah and I looked at each other at the same time and said "Damn...that made a difference!" I messed with the adjustment a few times trying to get the bog out but was unsuccessful. However, I'm optimistic I can tune it out so I'm going to play with it some before I give up and order a AFB.

The difference in performance is AMAZING. Probably 50% more pep (That's a scientific term measured by the impact of your head on the vinyl headrest times a universal constant of 1.000456 on Tuesday and 1.000455 the rest of the week). I'm pretty impressed.

A few weeks ago someone published a list of TQ part numbers and their applications. The shop manual says the needles are adjusted at the factory and should not be messed with in the field. But obviously there would be differences in calibration on the different engine applications. So I'll do some testing in semi controlled situations and see if I can make it work.

Question from John:

I put a Carter AFB Competition Series #9635 on my '65. It's a 625 cfm unit. So far the car is not very responsive and feels sluggish. My mechanic thinks I need more CFM. Note that I also have new rings and new bearings.

This carburetor was recommended to me by the local speed shop, who would seem to know.

I found some formulas online for calculating the CFM needs of an engine, and what I came up with is considerably less than 625 cfm for a 413.

I also looked around online at some speed/hotrod sites and it seems like people love to run giant carburetors.

Is this the same exact carburetor as the Edelbrock 1406? That one is listed at 600 cfm, and the tech at Edelbrock told me that Carter and Edelbrock are not one and the same; I thought they were.

He also said that unless I like to run my engine at close to max RPM, a 750 cfm carburetor would not help, and suggested I change metering to run richer.

To those of you that have replaced your carburetors, what has been your experience?

Does anyone know the CFM rating of the factory carburetor? (Carter AFB 3858) I'm told Carter did not publish that figure.


From John:

I have replaced the Holley that was on my '69 with an Edelbrock 1406 and am perfectly satisfied with it. I too asked around before making the change and with one exception, the 1406 (600cfm) was recommended over the 1411 (750cfm). Car starts right up, idles and runs strong. Feels Good!  If I had access to a gas analyzer, I could experiment with metering rods but I don't have have that luxury.  Other than adjustment mix screws and idle speed, my carburetor is as it came out of the box.

From Kerry:

I would be interested in the purchase details. Being only slightly better than your basic shade-tree mechanic, I still find carburetor tuning a matter of trial, error, and luck. I'd love to find a way to dial it in correctly without spending weeks diddling with it.

From Dieter:

I have a '55 Imperial Newport with a 331 cid engine and it had the factory single 4 barrel 450 cfm carburetor.  The car ran OK but I wanted a little more omph at a traffic light. So I took a chance and bought a new intake manifold from Weiand plus two four barrel Edelbrock carburetors each with 500 cfm's. To complement this setup I replaced the old 1- 3/4 exhaust with 2- 1/4 inch system . Also two low restriction mufflers HAD to be replaced.  I have no heat riser and no choke. The car runs excellent with NO bogging down at WOT from a stand sill as I was told from various speed shops who wanted to sell me the store.  They told me I needed a new camshaft with longer duration?? New heads also were recommended.  What they were right about was that my mpg will drop and that it did from 14 mpg at 60 MPH to10 mpg at 85-90 MPH.  That kind of speed was not possible with my old single 4 barrel setup. 

From Norm:

>He also said that unless I like to run my engine at close to max RPM, a 750 cfm carburetor would not help, >and suggested I change metering to run richer. 

This is good advice. It is easy to enrich the mixture by changing to stiffer rod springs and/or thinner rods. Get a carburetor book and follow accordingly. You do not need more carburetion than 625cfm.

From Bob:

After replacing my carburetor on my '69 a few months ago the car would still not run very well with the air filter in place. Take the air filter off and the car ran beautifully. So I thought it was a problem of not getting enough air. I purchased a 1" spacer which lifts the air cleaner off the carburetor, now the car runs great. I don't know if it was just dumb luck but it drove me crazy for over two weeks.

Follow-up from Kerry:

Funny you should mention this because I have noticed exactly the same thing on my Thermo-quad equipped '73. Runs like a bat with the filter off but put it on and it wants to flatten out at high RPM. Since I never drive it like this except when I'm playing with it I have not addressed it yet. However, looking at that little hole in the snorkel makes me wonder if it can flow enough air to feed the thermo-quad at full moan. Since pulling the filter off solves the problem I can assume it does not.

I noticed a car at Carlisle, PA that someone had taken a chassis punch and made about 20 1" holes around his air filter so it would breath better. Looked bad but probably worked well.

Since I have been playing around with the metering rod adjustments, I probably need to redo it with the filter ON after each change. I probably have it too rich for the restricted air flow or something....

Reply from Bob:

If your really needed it, probably could get more air by punching holes in the bottom plate (separate on yours?) with wrecking the appearance. Air would be hot, but still an improvement. Just a theory...

Reply from Richard:

Rather than go through the aggravation of creating something terminally ugly, that was only marginally effective, consider getting a K&N filter. They are more costly initially, but are useable forever and will make a real difference in both performance and also economy. I am sure that there is one that is close enough in size, that it could be adapted with minor effort.

Reply from Ed:

I discovered years ago that the air filter on my '69 Imperial was restrictive. Just couldn't see how enough air could get through that small snorkel to feed that big old 440. Sometime in the early 70's I changed the Holley carburetor on my Imp to a Carter and have never regretted it. I also changed the air cleaner to a dual snorkel unit from a '71 Mopar product I had at the time. Any way to make a long story short the set up has always worked fine and the Imperial performs really well. Oh I saved the original air - cleaner and use it at shows so the car looks original.

Reply from Mikey:

IF you have the room.....try and find a filter with the inside and outside diameters that are as close as possible as your standard filter for the car in question, but with more height!! This keeps the lid slightly open around the circumference of the filter canister, lets in more air compared to the snorkel but still is an effective filter!



I'm having a hard time in understanding why such painstaking trouble on so many aspects of these cars is spent as to authenticity and smooth operation, but then to recommend a carburetor which is a step backwards (Carter AFB or a clone) to replace a Holley just irks me. Yes, Holley's leak, they have this problem and that . . . but one of the professional tuners out there (and there are virtually none for Carter) can turn that Holley into the best responding carburetor you've ever experienced. The only advantage I can see to a new Carter beyond it's price is that it is less likely to need a rebuild from having sat around too much. Every problem I've seen mentioned has otherwise been addressed and improved by the aftermarket. The problem with the '67 Holley 3667 (570-cfm) can be corrected by blueprinting the carburetor and giving it more exact calibration than the factory did. Then it'll outperform any AFB out there in every parameter. About $250.00 for a customized performance rebuild from The
Carburetor Shop when a friend sent in his original Holley off of a Chevy a few years back. I swapped over to Q-Jets a dozen years ago when I found how much better part-throttle performance was on a performance rebuild by this shop, and I like it that I can tailor the cruise mixture to suit at any time with one simple adjustment.

But it requires an open, or spread bore, intake manifold, something Chrysler didn't go over to until the early 70's with the ill-fated Thermoquad. (Too
short a time in production for there to be much aftermarket support.)

(And, hell, I don't even LIKE Holley's that much. But I'd sure as heck have an original one re-done the right way.)

My '67 wears its original Carter AFB to this day, 122,000 miles later. I'd always recommend the Carter over the Holley for economy and reliability, just based on the many stories I've heard others tell me.

The Holley 4160 carburetors are not terribly complex but they do have some quirky areas that you need to check carefully during the rebuild process. As for finding a good used carburetors (Carter or Holley), that will be difficult (as you already know) and you never know what's been done to one when you do find it. Holley does make a Mopar replacement 4160 (#80454) but it is available in only electric or manual choke versions. Also, the fuel inlet pipe is routed differently. Carter also offers replacement carburetors. Expect to pay $200-$300.  

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