Carter AFB Carburetor Rebuild and Fuel System Troubleshooting

After Sherman was pulled out of the junkyard, I couldn’t get his factory carburetor to work. I simply purchased a “rebuilt” unit off eBay to get him driving under his own power. Later, I had that same carb tuned by my mechanic, and it seemed to work well. After the rebuilt engine was returned in late 2019, I put that very same carb on top of the engine and the results were less than spectacular. I had thought it worked well before, so why mess with success? After talking to the experts, a rebuilt carburetor or fuel injection would be what I needed to get the new engine to perform well.

I chose to have the factory original carburetor rebuilt by Tom Telesco in Connecticut. I sent the eBay unit strictly to have parts harvested from. Tom did great work, and it was returned far quicker than I expected. Please watch the videos below to see the symptoms that led me toward getting the rebuild, and the surprises I found along the way.

Below is a before and after of the factory AFB. You’ll notice the choke housing is completely missing on the before picture. The choke was removed in the 70s while my father, and thus the car, were stationed in the Philippines. After, you will notice all the brass and steel is shiny, and a new aftermarket Edelbrock choke housing was installed. The choke housing from the other carburetor was warped.

Below is a before and after of the choke side of the carb. You’ll notice as-sent to Tom the mechanical lockout for the secondaries was missing. It is amazing what he was able to do with such a train-wreck of a source carburetor. You also see a black cap on a brass tube at the air horn. This was the original source of air for the hot-air activated choke circuit, but I have an electric choke in place now, so the cap prevents contaminants from entering the carburetor.

Below, the Rochester 4Jet from my 1962 Nailhead that crowned my Nailhead during the AFB rebuild. I went manual choke for the duration of running this carburetor (not shown in pictures, but is shown in video above). In order to adapt the carburetor to the newer throttle linkable, I sourced an Edelbrock 12413 Carb Throttle Ball Assortment kit, and found the proper ball to fit my carburetor.  

Below, the new carb is rightfully installed in its place at the top of the engine.

When I took the car for test drives, I had odd experiences with a bog that occurred whenever I got well into the throttle, but it was an intermittent problem. Consulting with Tom, I did some test like running the car off a separate tank of fuel, and changing my electronic ignition out to points. As I talk about in the video above, Tom runs these carburetors on a Riviera before sending them back. This is the ultimate in plug and play, and knowing the carb will work on a Nailhead. When I reached out to Tom he'd never seen an issue with a carb he'd rebuilt, but stood completely by his work and let me send it back to be re-worked. Tom completely rebuild the carburetor again at no charge, and again tested it on his Riviera, putting 27 miles on it. It arrived back in speedy fashion, however the throttle linkage did arrive bent, but nothing a Craftsman screwdriver couldn't fix.

When I put the carb back on Sherman, it worked absolutely fantastic the first time I took it for a spin, but the second time got the bog again. I would keep driving it, and with little rhyme or reason, start messing up, for instance with half a tank of gas when going around a corner, but not every time. Discussing this in depth with Tom, he honed in on the fact it was likely a fuel delivery issue 
under load. Being a retired mechanic (I would call him semi-retired) he recounted stories with issues with fuel hoses, and I shared I had never replaced the hoses at the back of the car. With the recommendation to check the fuel pressure under load, I purchased a remote, electric 15 PSI fuel pressure gauge.

I first bought a Holley 26-503 for $106, but I found out it was severely inaccurate (by pounds) and the needle would stick. The Holley is really a re-badged Faria marine gauge, hooked to a Stewart Warner M-82504-F. One installation concern that came up is the gauge sender has no provision for a ground connection; the expectation is that it will be grounded through the fuel system. On my Buick, there is a rubber line feeding the carb, and no way to provide a ground other than carefully soldering one to the sender. This combination was returned. Next, I purchased a Glowshift brand Maxtow MT-DV11_15 -15 PSI gauge for around $100. When checking it for accuracy, I found it was also off by pounds. Calling tech support, they stated there was no adjustment available and I would need to send it back and they would see if it was inaccurate, at my expense. I had asked if they could send a different sender, to see if that was causing the inaccuracy, but same answer: send it back at my expense. I opted to just send it back to Amazon at their expense. 

The last gauge I purchased, which I kept, was a Quickcar 67-000, for $90. It is about 1/2 pound off, but was the most accurate of the three, and also the most expensive. I believe this was another lesson in "you get what you pay for". The others came with a sender included, but the Quickcar required the purchase of a separate 63-240 pressure sender for $80. I went this route of a separate gauge/sender because I decided if I couldn’t get an accurate gauge, I could build my own with the sender. Tom would call me for status updates (talk about great follow-up) and was very patient while I was going through gauges getting one I could trust. He recommended taping a mechanical gauge to the windshield for the same result, but I wanted to stay electric as I may integrate it into my gauge cluster in the ashtray one day.

Below, once the gauge was hooked up, the left picture shows that under acceleration the fuel pressure was going into the sub 1 PSI range, even though it was normal at idle. I then replaced the fuel hoses at the back of the car, along with the fuel sender. While replacing the sender, I found a toy carrot in the fuel tank! See the whole story here. Once the carrot was taken care of, fuel pressure under load stayed great, as shown in the below right picture. I feel like this explained the intermittent issue with the bog when running out of fuel. If the tank was full, nothing was holding that carrot from floating around, but with a low tank that toy carrot likely made contact with the only thing hanging down in the tank- the sender/fuel gauge.

With the fuel delivery issue resolved, I decided to do a fun test now that the engine has been broken in. It passed with flying colors, and was measured in smiles per gallon. Stayed tuned for the next adventure.