Trying to get the two rear air horn screws loose on a quadrajet (see picture). I've had them soaking in acetone/ATF for a week, tried heating the casting with a small butane torch... One of them moved two turns then re-seized. Anybody have experience with this issue and have any tips for getting these out?

It's a 7028255, so I don't want to damage it.

 

Sounds like you are on the right track
grind a good screwdriver to EXACTLY fit the slot, preferably with straight or nearly straight sides at the engagement surface.

Continue with light heat on the outer part, voodoo juice, and turn back n forth.

repeat.

I have found candle wax on a heated part to penetrate and lube even better than ATF/Acetone. Worst case, carefully grind or drill off the screw heads, take carb apart, then you will have better access to the screw shank, and can heat just the base plate which is presumably easier to replace than a '8255 body.

 

What have you been soaking, exactly? Obviously the threads are in the throttle body, and I believe the holes may even be open to the bottom. If that ultimately proves unsuccessful, you can cut the heads off carefully, pull the air horn and main body off the throttle body, and grab the remaining parts of the screws with a vice grip pliers. Worst case, you put helicoils in the throttle body holes.

 

As above, go to the mounting surface of the throttle body, spray with Mopar rust penetrant several times over a day or two.

 

Thanks everyone. I've been pumping the acetone/ATF mix down the shaft of the screws, so it puddles down around where it threads into the carb body.

I'll try to see if I can get the throttle body off tomorrow to check if this is a blind or through hole. If I can soak these from underneath it may be more effective.

 

try seafoam deep creep...works better than anything ive ever used except brake fluid..it wicks, give it a couple days

 

So those back two screws actually thread into the throttle plate/carb base, so they just pass through the carb body. You can actually see the holes if you flip the carb over... this one had the base plate gasket RTV'd to the engine at one point, so the hole were full of black silicone.

Anyways, I used the butane torch to heat the base, the first screw grudgingly came out. The second one is stuck solid... I even took the mapp gas torch to it, and it won't move. So I have the carb upside with the screw hole filled with acetone/ATF. If it doesn't work, I'll give the seafoam deep creep or candle wax a shot next.

Thanks!

 

Be careful with the heat. I melted a carb body once.

 

You may ruin the screw but try a good vise grip clamped on to it. It will give you alot more leverage.

 

I ended up having to cut the screw with a dremel cut off wheel to get the air horn and main body off. I was able to cut it without damaging any of the carb.

I double nutted the remaining screw, tack welded the nuts in place, heated the base with MAPP gas, and all I succeeded in doing was breaking off the screw where the nuts were. I have plenty of screw left to grab, so I have the base soaking in more penetrating oil. I've never had anything this bad before.

 

I'm impressed.

Try heating the screw dull red with the torch.

- Eric

 

I always appreciate updates in threads like this. If heat isn't working, maybe cold would do the trick?

 

You could try soaking the base plate in 50% Pine Sol, 50% water solution. I've used it many times to clean carburetors. It works well and isn't as caustic as PB Blaster or brake cleaner.

 

I gave it hell one last time tonight. I welded a 1/4" nut to the protruding stud, welded on both sides. Had good penetration but didn't thin the stud either. Got the stud hot, heated the heck out of the base. Instead of twisting it with a wrench, I hit it with my 3/8" dewalt impact... and the stud just broke off again where the nut was welded to it. The screw must be getting brittle when welded.

Either way, this thing is stuck good. I don't need this carb for a while, so I threw in the towel for now and put it all back together. I'm guessing it will eventually end up being drilled out and re-threaded.

 

Have you tried tapping on the screw to break the seal? Could also use a small drift to tap from the bottom side. I don't mean going medieval on it just some taps with penetrant on it.
Might also try flipping it over and filling in the end of the screw hole with paraffin wax. Then heat the screw until it melts. Tighten the screw slightly first then back it out.

 

Who would have thought a screw in a carburetor base plate would be seized so solid? Good luck!

 

Yeah, I have a small trim hammer (for removing dents from stainless trim and such) that I was using to tap on it. I was hoping the 3/8" impact would help by adding vibration that would loosen the screw and get away from the out of plane bending loads a wrench typically adds.

My main goal was to look inside the carb and see what was there (and confirm it has the original correct 7028255 jets/rods, which it did). I figure I'll save this project for another day, and keep actually progressing projects that will get my car on the road for now...

 

Luke, I'm pretty sure you wont rest until that $@!&% screw is out.

 

Had a 69 Toro carb do that to me once. I finally gave up since Toro carbs aren't that difficult to find.

 

Wax, where have I heard that before ??

I have gotten exhaust bolts out that were rusted down to about 1/4" diameter, using lots of heat.... and WAX.

Now, you are limited on the heat you can use.... but heat & wax are effective.

Also remember that now you can turn BOTH DIRECTIONS. just apply moderate force and keep reversing it. I hope when you applied the impact, which i was also going to suggest, you used less than full throttle. Repeated low level impacts, both directions. After heat and wax.