Vintage Mustang Forums banner

1 - 16 of 16 Posts

·
Registered
Joined
·
529 Posts
Discussion Starter #1
Last year, I bought an Autolite 4100, 1.08 for my 65 Mustang really cheap. Stock 289. I got it cheap because the right adjustment screw was seized in the carb and broken off. We carefully drilled the screw and had to re-tap the hole. Problem is, we could not get it cleaned out all the way through the idle bleed hole in the bore. I had no choice but to drill it through with a very small bit. The hole ended up being a little bigger than the other side. I cleaned up the carb really well and made sure all the passages were clear and threw it on the car. It started right up and has fantastic throttle response but it will not idle. Also adjusting he screw I had to repair doesn’t seem to change much. It WILL idle with the choke closed which makes me think I have a vacuum leak.
Thoughts? The guy at Mike’s Carburetor Parts said that I should just get a new carb but I thought it wouldn’t hurt to try it. Would the hole being a little bigger make it not idle? I need to check for vacuum leaks but ran out of time.
 

·
Registered
Joined
·
899 Posts
I have very little experience with the 4100, but the one 4100 I do own had a crack that looks like casting flaw. You may want to check your carb body for the same issue. I used JB Weld over the crack.
 

·
Registered
Joined
·
5,046 Posts
  • Check the bottom of the carb for flatness with a straight edge. If it isn't put a sheet of 220 grit on an old window sash and re-true that surface. Does not take much to get ther, so go slow.
 

·
Registered
Joined
·
35,979 Posts
The hole is sized for the needle to fit it properly. That has now changed. I second the suggestion to salvage whatever parts you can and toss the base.
 

·
Premium Member
Joined
·
4,405 Posts
Or fill it completely then drill it for the right size orifice and drill and tap for the right screw.
 

·
Registered
Joined
·
35,979 Posts
Or fill it completely then drill it for the right size orifice and drill and tap for the right screw.
I don't think that'll work... something in the back of my mind tells me that the orifice is tapered/stepped...
 

·
Registered
64 1/2 D Code Coupe,
Joined
·
3,326 Posts
I don't think that'll work... something in the back of my mind tells me that the orifice is tapered/stepped...
I believe you are right. The A/F screws are tapered as well. If they're tightened too much it enlarges the holed and screws up the ability to adjust the carb. There used to be a shop that specialized in 4100s that said they could repair any problem with a 4100 but they are no longer.
 

·
Registered
Joined
·
529 Posts
Discussion Starter #9
I really have doubts that I will be able to salvage this one, but I'm going to check everything for a vacuum leak. If there is none, I may just look for another 4100. I bought this one knowing there was a chance it wasn't salvageable but what's it hurt to try, right?
 

·
Premium Member
Joined
·
4,405 Posts
You can always donate it to me !!
 

·
Registered
Joined
·
529 Posts
Discussion Starter #11
Well, after watching some videos on what all the holes in the carb are for, and doing some more reading, I'm going to try to rebuild it. There are several air holes on the primary venturi that are for idle. So I am going to soak the carb for a while and then blow all the holes out (they are very small and I didn't even notice them) and gently run a wire through them if necessary. Also, I plan on putting JB Weld on the hole I drilled and try again with a smaller bit with a dremel. I really don't think that's the problem, but it appears the hole is off center just a little bit so we will see. I'll rebuild and try it first before I go through all that and report back. The carb is so complete and in great shape otherwise, and with the costs associated witha replacement (and they are hard to find) I really want to save this one. If I can't, I may go with the Summit Racing 500 cfm carb, if I can't find a replacement in Columbus at the swap meet this year. Anyway I'll let you guys know. Thanks again for taking the time to respond to my posts!
 

·
Registered
Joined
·
35,979 Posts
Well, after watching some videos on what all the holes in the carb are for, and doing some more reading, I'm going to try to rebuild it. There are several air holes on the primary venturi that are for idle. So I am going to soak the carb for a while and then blow all the holes out (they are very small and I didn't even notice them) and gently run a wire through them if necessary. Also, I plan on putting JB Weld on the hole I drilled and try again with a smaller bit with a dremel. I really don't think that's the problem, but it appears the hole is off center just a little bit so we will see. I'll rebuild and try it first before I go through all that and report back. The carb is so complete and in great shape otherwise, and with the costs associated witha replacement (and they are hard to find) I really want to save this one. If I can't, I may go with the Summit Racing 500 cfm carb, if I can't find a replacement in Columbus at the swap meet this year. Anyway I'll let you guys know. Thanks again for taking the time to respond to my posts!
You'd probably be better off using solder in the hole, drilling it to the tip size of the needle then trying to find a reamer with the correct taper to re-form the hole.
 

·
Registered
Joined
·
529 Posts
Discussion Starter #13
You'd probably be better off using solder in the hole, drilling it to the tip size of the needle then trying to find a reamer with the correct taper to re-form the hole.
Actually, the taper of the hole seems to be ok. I never thought about soldering it. That’s a great idea. Just going t be hard to get the hole in the right place.
 

·
Registered
Joined
·
35,979 Posts
Actually, the taper of the hole seems to be ok. I never thought about soldering it. That’s a great idea. Just going t be hard to get the hole in the right place.
Is it just the threads that are boogered?
 

·
Registered
Joined
·
529 Posts
Discussion Starter #15
The threads are fine. When I bought it the screw was broken off and seized. We had to drill out and re-tap. When I drilled the hole it’s just slightly too big and slightly off center. But luckily the threads are good and the taper is still there. I still think the hole may be ok and one of the idle air holes is plugged. So I’m going to clean it really well again and rebuild and see how it goes and report back. If that doesn’t help I’ll solder the hole and try again. I’m determined to save this one!
 

·
Registered
Joined
·
35,979 Posts
The threads are fine. When I bought it the screw was broken off and seized. We had to drill out and re-tap. When I drilled the hole it’s just slightly too big and slightly off center. But luckily the threads are good and the taper is still there. I still think the hole may be ok and one of the idle air holes is plugged. So I’m going to clean it really well again and rebuild and see how it goes and report back. If that doesn’t help I’ll solder the hole and try again. I’m determined to save this one!
You can use piano wire to "run" the orifices and passages to knock out anything that may be plugging it up.
 
1 - 16 of 16 Posts
Top