So, I'd made up my mind and how much can a beat-up old 40+ year old carb cost anyway? Can't be more than... what? 60 bucks? Well, like everything else I get into, it seems, the prices skyrocket for one reason or another. In this case, I think one or more of the Mustang rags wrote a glowing article regarding the 4100 and how to adjust it a few years ago and now you'd think these things were cast out of gold instead of aluminum and brass. One company even restores them to better than new for just under 800 clams. Well, I have to admit, they ARE beautiful. They even go to the trouble of re-plating the carb and updating it for modern fuels and such. However, for me, this is not a show car. I just need the carb to atomize gas and feed it into the intake manifold. I don't need a work of art.
So, I watched eBay for awhile to get a feel for how the market is for these cores and it looks like I could get a "this was working when I pulled it" carb for around $250-$300 or a core for around $100. My research shows that if the most popular carb is the 4100, then the most popular year for the 4100 is the last year that it was put on a 289 Mustang, 1966. Hi-Po versions of the carb beat out the competition due to their rarity and the price of a core reflected that. For me the, best flavor of 4100 would be a 1966, 1:08 venturi. Since I'm not in "concours" mode, I'm more concerned with functionality (and price!) than correctness. So, I pulled the trigger on this C6PF-H that I found on eBay for $125. It looked complete from the pics, had the desired "short snout" pump, and met the 1966 1.08 venturi requirement. Although the actual number C6PF-H stands for 1966 Ford Service Replacement (not original to a particular Mustang), it's 480 CFM rating would still probably be good for my mild 289 engine.
|The pic that was on eBay|
There were a couple of 4100 rebuild kits on eBay and various Mustang vendors that cost $50. The vendor excuse for charging $50 was that THEIR kit included the secondary diaphragm that is rumored to be missing from the everybody elses kits. I decided to search some more and found THIS kit from Mustangs Unlimited for $27 that plainly shows the secondary diaphragm and otherwise looks complete so I bought that one instead. Well, I got it and the contents are complete but not exactly like the picture on the MU web site. For instance, there was only 1 horn-to-body gasket instead of the two shown and completely different needle valve assemblies than shown. The kit is good though so don't let those details deter your decision. I laid out some paper on the bench and starting disassembling the carb marking the paper where I laid the parts with their sequence in disassembly so I could just reassemble in the opposite sequence. Also, I took many reference pictures.
|Not the kind of dirty body I like to see.|
|Dunking the carb in cleaner.|
|As clean as I could get it. Nasty oxidation in the secondary bowl.|
|Newly fabricated tube next to original that took some damage being removed.|
|Flared end comparison.|
|New emulsion tube installed.|
|Venturi cluster gaskets on primary with ball and weight (center hole).|
|The secondary diaphragm assembled compared to the original.|
|Secondary diaphragm and lever in position.|
|Secondary pump cover with lever and pin in place.|
|The "economizer valve" installed with gasket.|
|Economizer valve cover.|
|Primary pump sitting on it's spring.|
|Primary pump lever and cover ready for business.|
|Funky new needle valve compared to original valve seat.|
|Float assembly for the new valve.|
|Float mounted in the bowl on the new valve.|
|Adjusting the float. Just bend the tang up or down.|
|Floats, venturies, and pumps installed.|
|Throttle levers installed.|
|Getting a leg up.|
|Choke, linkages, and bowl cover gasket in place.|
|Bowl cover bolted down.|
There are quite a few steps in the adjustment of the 4100. All of these adjustments are listed and described in the instructions that came with the kit. One of the weird adjustments was the "choke valve pull-down adjustment". This involved sticking an 1/8 gauge in the choke piston hole, clamping the lever in that position (gently), and then measuring the gap between the choke plate and "air horn wall". In this case, it had to 1/8". The choke plate adjust nut was turned to get the correct gap.
|Gauge inserted into the choke piston.|
|Checking and adjusting the choke plate gap.|
|Done! Choke side. There's still a heat shield that goes over the choke but I'll put that back on later.|
|Done! Throttle side.|
Autolite 4100 Adjustment Instructions
Update 8/7/2012: I found an interesting thread on Ed's Carburetor Forum that mentions "6P-H" type carbs and labels them as the most generic and thus least matched of all of the 4100 carbs. Read up and decide for yourself if you're thinking of getting one.