'66 Carter AFB Question(s)

[Guest imported_Thriller]

I had asked about this in the Me and My Buicks forum, but thought perhaps I should ask here too in case there are (gasp) people who don't look over there. I'm spending a lot of money (as I don't have time / tools / work space) to get my '66 Wildcat ready for Rochester. The shop suggested I'll be needing a new carburetor. My understanding is that my car has a Carter 4054S. The next paragraph is what I wrote in the other thread.

Now, I knew the carb was in tough shape. They are suggesting it will need replacing. I spent some time looking around (particularly at The Carburetor Shop) online today. I think this car was supposed to be a Carter AFB 4054S. I found they list the 4053S and 4055S as available replacements. Does anyone know the difference among those carbs? I think I'd like to stick as close to stock as possible.

Are the 4053 / 4055 direct replacements for the 4054? Or are they a bit different?

Thanks.

[Guest 1964 225 Roadster]

They DO list a kit for the 4054. It is Kit # 859, which is the same kit as listed for the 4053 and 4055.

http://www.thecarburetorshop.com/Kbuick3.htm

The 4054 is the eighth one up from the LAST 1966 entry.

They are extremely particular, so the differences must be in other minute details of the casting, etc. The 4054 was a regular production unit for 1966, or they wouldn't have it listed.

[NTX5467]

If the kits are the same for all three part number carbs, then the kits either come with a selection of some gaskets or the gaskets are all the same and it's a calibration issue rather than a casting issue.

Calibration issues might relate to particular transmissions, with or without a/c, or California emissions back then (generally a leaner main system calibration, I suspect). These differences could be in the metering rods and primary jet combinations (metering rods were generally "two step" rods for that year of AFB) and possibly power spring differences too. Might just be different secondary jets OR a different counterweight for the secondary air valve setup, if it has one. Other calibration areas in those carbs were the air bleeds in the venturi cluster AND the low speed jet in the bottom of the idle tubes--things that are there but you don't generally worry about in a rebuild, but are important for things to work "as designed".

Somewhere . . . I've got an old Carter Strip Kit for AFBs which has a listing of carb numbers and metering rod/jetting for each one. I bought it for a Chrysler application, so it might not have non-Chrysler listings--don't recall. The Buick Chassis Service Manual for 1966 might hold the key, though!

About the only "wear" area in those carbs was the throttle shaft for the primary side. Just as with Rochester carbs, they can generally install bushings in there to put things back where they need to be. If the accel pump bore is worn, that might take a little ingenuity to compensate for. From experience, the primary power pistons tend to be a little loose in their bores, but that looseness is generally calibrated around in the carb's basic metering calibration map.

Might be that The Carb Shop could recondition your existing carb rather than chase a NOS or rebuildable carb of the desired number?

Just some thoughts,

NTX5467

[carbking]

The 4053 was used on the 401/AT. The 4054 was used on the 401/ST. The 4055 was used on the 340/AT.

AS A GENERAL RULE! Given the same engine (heads, cam, exhaust, etc.) carburetors for an automatic transmission will be calibrated from 1/2 to 2/3 size richer through all metering circuits than the same carburetor for a manual transmission. This is necessary to compensate for the fluid coupling losses of the converter/transmission; and just one of the reasons it is impossible to obtain the same fuel economy from an automatic transmission as a manual one.

As to interchange:

A carb for the automatic may be used on a manual vehicle with a slight (but measureable) decrease in fuel economy.

A carb for the manual WILL RESULT IN IDLE ISSUES if used on a vehicle with an automatic.

Migrating O.E. carburetors across engine sizes (340 -> 401) is not a good idea. In general (unless one is a carburetor technician), a good rule of thumb for migrating O.E. carbs is that the displacement of the receiving engine be within plus or minus 3 percent of the donor engine. Thus 3 percent of 340 is roughly 10 cubic inches; thus the 340 carb could be used on engines from 330 to 350 CID.

Specifically, in the question above: the airbleeds are different in the standard vs the automatic carburetors, while the gasoline jets are the same; the same general casting is used, but machined differently. Thus the repair kits ARE the same.

A comment concerning another post in this thread: Carter understood that the "coefficient of linear expansion" for aluminum was great compared to the figure for cast iron, and designed the AFB (aluminum four barrel) accordingly. If one looks at the throttle shaft bearing surfaces on the AFB, one will find extended areas in the body, thus much more bearing surface. This additional bearing surface helps throttle shaft stability and the lessening of leaks. Because of the expansion, the design tolerances on the clearance of the throttle shaft to body on the AFB are 0.016 ~ 0.022. Contrast this to the Rochester or Holley which used 0.004 ~ 0.006. A mechanic not familiar with the AFB might suggest that the AFB needed bushing when in fact it would be right in spec.

These are some of the most "bullet-proof" carburetors that were ever produced.

Jon.

[carbking]

NTX5467 - you mentioned the vacuum pistons. This is another example of excellent Carter engineering. Carter was aware that wear would be a problem, so the vacuum pistons were deliberately constructed from a "softer" grade of aluminum. The vacuum pistons are "sacrificial" (sp); they wear to protect the main casting from wear. When rebuilding an AFB, it is good practice to replace the vacuum pistons.

Jon.

[NTX5467]

In some cases, there are parts of the Carter design that look "sloppy" compared to what Holley or Rochester did. Kind of like it was designed to be less precise in operation . . . but they work very well and reliably.

One other observation . . . a "fixed jet" carb (i.e., Holley or similar) might not get quite the same level of cruise fuel economy as a "metering rod" carb. In the fixed jet carb, once the main system is fully operational, that's it, until vacuum levels drop such that the power valve/piston opens for added enrichment under load. This might result in a soft spot in the pedal response and then more pedal actuation as a result. Circa 1972, Holley started using a 2-stage power valve that had a first level of enrichment at 10.5" Hg with full enrichment at the normal 5.5" Hg. This let them meter their carbs' primary side main system circuits about 2 jet sizes smaller for emissions and economy (the economy part was generally lost with the lower compression ratios, though).

In the case of the AFB, the metering rods had two steps (Economy and Power), whose interface with the fuel jet in the bottom of the float bowl was modulated by the power piston springs. Similar in concept to the "on" or "off" enrichment, but was possibly better tailored AND could be changed with very little effort. With the AVS, "three-step" rods were introduced with a little different power piston design that appeared to have less leakage (via more ribs, if I recall correctly). This allowed for a similar transition from "economy" to "power" as the two-stage power valve, but in a more gradual manner. It also allowed for a more finely tuned fuel curve in the process too.

QJets were similar in this arrangement (three-step metering rods). In the Rochester Carb book, it mentions using "metering area" as the real tuning device rather than just changing jets and rods with abandon. Using the stock calibration, you determine the metering area (jet size - rod diameter) for each of the three metering rod steps. This way, one aspect of the fuel curve could be changed while also minimally affecting the other aspects of the curve, yet putting the fuel mixture at the more optimum value for the particular operational parameters of the engine/vehicle interface. The Rochester Carb book went through this procedure, which was somewhat time consuming without a chassis dyno to work with.

Other magazine articles have documented how the current Edlebrock AFB can be recalibrated to match the engine it's mounted on with increases in power and economy too (from the base "generic" application calibration). Same things with the prior AFBs and AVSs and can also be done (with more disassembly/assembly time) with QJets or other metering rod carbs.

When the electronic control carbs of the 1980s came in, the metering "kit" came assembled and application specific. No way to really tell what was what, as compared to jet and rod sizes as the control solenoid did it's job according to the computer controls from the ECM and oxy sensors. You could suspect that a metering kit for a Chevy 350 would flow more fuel than one for a Chevy 305 or 4.3L V-6, though, but not real way to document that fact.

So, my observation from times past was that Holley 4160s had crisper throttle response, but my Carter AVS (in a medium-priced luxury oriented car) would get about 1-2 mpg better than a friends car with the same engine (in an intermediate car) with comparable tire size/rear axle ratio combinations. Back then, the only people that seemed to like Holleys were the people that knew how to work on them, whereas when you put on an OEM Carter AVS in their OEM place, they ran well, and needed no yearly rebuild. Kind of how the Holley got the reputation as a "hot rodder's" carb? After Holley changed their metering block/float bowl gasket material, they are pretty much maintenance free (in OEM replacement applications), from my experience.

But while Holleys were generally for Fords (until Ford did their own 4bbls), Carter did OEM carbs for GM and Chrysler as a matter of course. Plus Carter also did aftermarket 4bbls too. Remember the old J. C. Whitney catalogs from the middle '60s that touted "venturi area" of a Carter AFB as the determiner of performance capabilities? This was before Holley jumped into the aftermarket and factory performance markets circa 1965 and started quoting air flow rates (cfm) with respect to carburetor size classifications. 4bbls rated at 1.5"Hg and 2bbls rated at 3"Hg, from what I've read in the Holley Carb book (HP Books).

Carbs can be highly interesting creatures, if you understand what makes them tick and how and why.

. . . and then there's the decal I saw on a quarter window at a car show recently . . . "Low Carb Diet. Only 3 Carbs . . ." which were mounted on a Chrysler 440 V-8 in a '65 Plymouth Belvedere 2-door hardtop. Had to smile at that!

Enjoy!

NTX5467

[Guest imported_Thriller]

Wow. Thanks for all the responses, even if it did get over my head in a hurry. Don, I saw that they had rebuild kits - the shop suggested to me that the carb may need to be replaced, not just rebuilt, which is where my question came in.

If the 4053 was for an automatic, but not the Super Turbine, was it the older one used on the Dynaflow equipped cars?

I'll be stopping by the shop where the car is at in the morning to take some photos. I will try to get more details as to why they suggest replacing the carb as opposed to rebuilding. The mechanics are much closer to experts than I am and presumably saw something that made them suggest replacement. Perhaps I'll have a photo or two as well.

As for sending it away for refurbishing, I am leery of sending it across the border. It has nothing to do with the company, it has everything to do with how Canada Customs decides to handle it when it is coming back. The other thing is that there may be issues of timing in the overall refurbishment of the car.

[Guest imported_Thriller]

Well, I talked to my guy today...I guess we had a failure to communicate...since he was talking about parts that should be replaced, somehow I lumped the carb in there. They'll be sending the carb to a local rebuilder who is very reputable for evaluation / rebuild. I guess we'll see how things go.

Thanks again for all the input.

[Prevost]

I was hoping that someone could direct me were I could get the floor Pans and body mount bushings for a 66 Wildcat?

[Philippe Racicot]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">

If the 4053 was for an automatic, but not the Super Turbine, was it the older one used on the Dynaflow equipped cars?

</div></div>

Hi Derek,

In this case, I think AT meant <span style="font-style: italic">Automatic Transmission</span> and ST was for <span style="font-style: italic">Standard Transmission</span>, not Super Turbine... Are you sure about your carb # ?

[Philippe Racicot]

I have no experience with older Rochester carbs like the 4GC or 4GV models but the Carter AFB I have on my 65 seems to be more reliable than the early Quadrajets I had so far... My 68 Quadrajet 4MV gave me quite a few problems but my 67 4MV is by far the worst! The main problem with the 67 is fuel leaks at the fuel inlet and at some plugs in the casting. Mine is also the early 67 with the needle and diaphragm but it was converted to a conventional needle and seat when rebuilt. I had 4 67 carbs to choose from when I had it rebuilt and all of them had leaking plugs (covered with epoxy) and fuel inlets (modified in the past or glued)... The 70's Quadrajets didn't give me trouble so far and the 75-76 4MC seem to have a better choke system.

[carbking]

Philippe - your experience pretty well says it all.

The older Rochester 4-G series was very reliable; but the Q-Jet is a much more efficient design.

The Q-Jet came out in 1965 (Chevy got them first), and earned the title "quadrajunk" some 7 or 8 nanoseconds after the first car was delivered to a dealer.

The 1965 had major issues. The 1966 had issues. The 1967 had issues, but they are addressable by a competent carburetor rebuilder.

By 1968, the Q-Jet was/is one of the finest street 4-barrels ever produced (in my opinion, second best of all time behind the Carter TQ). It still had two issues: (1) the fuel inlet threads (which normally may be helicoiled), and (2) the lack of throttle bearing surface (may be corrected by installing bronze bushings).

The circuitry inside the AFB is probably as good as that of the Q-Jet, and the AFB does not suffer the reliability issues of the Q-Jet. The AFB, on the street, however, is somewhat less efficient than the Q-Jet by reason of the fact that the AFB is a "square-bore" and the Q-Jet is a "spread-bore".

Once the spread-bore was fait accompli, the square bores pretty well died out for passenger street use. The Q-Jet, the Carter TQ, and the Autolite 4300 were used on virtually all passenger 8 cylinders in the 1970's.

Jon.

[Philippe Racicot]

I have to say that the Riviera with a 430/Quadrajet and a 3.42 rear has better performance than my 65 Wildcat with a 401/single Carter AFB, 3.07 axle and a very similar transmission.

However, the Wildcat, even with a less efficient carb and less efficient engine design is still more fuel efficient than my Riv is (mainly because of the axle ratio and smaller engine I guess). The 65 also has a better top speed than the 67 and it has a more solid engine.

That's something I wouldn't try with my 67, even with it's freshly re-rebuilt 430 engine!

And I did go above that speed a few times with the 65!