FE Power Forums
FE Power Forums => Non-FE Discussion Forum => Topic started by: djburton on January 19, 2026, 10:40:54 AM
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I have this 4100 carb. This thing is complete and untouched. I want to use it on period correct 66 Fairlane GT S code. The only issue is the secondaries are stuck. Been soaking in Kroil for a week but no go. Any thoughts on this? It's a really nice carb and I don't want to screw it up. Thanks!
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Are you sure about that carb being correct? They used a 600cfm vacuum secondary Holley on the GTs I drove back in the day. Joe-JDC
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I've fought stuck throttle shafts, twice on 4100's.
On the last one I used CRC Ultra Screwloose. One the first one, I ruined the shaft to lever connection but, with the CRC I socked it 5 times, then heated it, sprayed again and it moved.
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Patience will be your friend here.
Kroil is good penetrating oil, maybe the best, so you are already on your way with that.
Use some heat to help soften old goo (gas, oil, other) but don't get too greedy with the heat. Use a heat gun (not a hair dryer) to heat soak the entire area around the shaft in the carb body.
If you have access to an ultrasonic cleaner, you can try that with some safe solvents.
Heat the carb up, then toss it in the cleaner and let it sonic soak for about an hour.
Disconnect all linkages to the shaft being worked on to ensure you are only fighting the stuck shaft and nothing else.
One you have things heated up and soaked plenty then try moving the shaft forth and back.
Remove the nuts on the outer shaft and use a tool directly on the milled end of the shaft (be careful though).
With the shaft free from other parts of the carb linkage and plenty soaked and heated, if you are not able to s l o w l y get things to move open and closed, even just a little bit.
If this does not work then you can try coaxing the butterfly open with a wood dowl and a hammer... use gentle taps because it is easy to bend things and ruin them. But with careful force applied you can usually work even very corroded butterflies open eventually.
Again, be patient, let thing heat and soak, heat and soak, heat and soak, moving them from time to time to see if any further movement has been attained.
Eventually you will get things moving enough to fully open the butterflies, but this does not mean you have solved the problem just yet.
There can be a corroded/rusty/rough shaft inside the carb body and that stuff will wear the shaft hole pretty quickly if you try using the carb.
The shaft may be bent, or twisted, causing the binding.
The butterflies can be rusted, bent, misaligned too.
Keep at it, be persistent and patient and methodical and it will come loose..... eventually.
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Like Joe said, my 66 Fairlane GTA came with a Holley 600 carb, not an Autolite 4100. I believe that an Autolite carb was used on the Z code 390 engines, but the GT/GTAs in 66 and 67 had the S code 390s, which was only used in the GT/GTA version.
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Thanks, gentlemen! Yeah, I know it's not correct but the date matches perfectly with the car. It's not a numbers matching deal anyway so the appearance of originality is all I'm looking for. The guys I hang with are more into chrome than correct but I guess they appreciate the effort.
One more question...Are the plate screws staked and will there be any issues removing them? Thanks again!
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If you want a little closer to correct, I have a couple original 600 "GT" carbs, on a '67 and another a '68, and a parts '68. I used to run them on my 351W, pretty good runners