Autolite carb frustrations

66newbie · Sep 10, 2006

I have a rebuilt Autolite 4 barrel. I look at the choke and it's slightly open. I never adjust the screws at all.

I put the carb on but I realize that my heat tube coming off the exhaust manifold is rusted and broke off.
I get the car to start but it idles rough, I pull the throttle linkage and the choke plate snaps completely closed and the idle goes up (a little to fast of an idle)
I pull the throttle linkage back again and the choke plate resets to an opening of 1/4" (estimate) and it idles rough.
I can repeat the above last two steps.
I let it idle roughly for a few minutes and it dies completely.
I can't get it to restart until I let it sit for a while.

I have checked for vacuum leaks and I am pretty sure it's air tight.

How big of a difference does the heat tube make ? I have the heater hose next to the choke like it's suppose to be.

Is there a hose to release the air coming up from the heat tube ? Cause I don't see a connection for that.

What is causing the choke plate to do that ?

whosgt · Sep 10, 2006

i would suggest buying a road demon and being done with the problem all together. you are going to have nothing but problems with this carb from now on.

tweet66 · Sep 10, 2006

I have a 525 cfm Demon carb that I'm selling for $200 + shipping if your interested. I went with a 351 and bigger cam so I switched to a 750 Holley. Only used for 4 months on my 302.

66newbie · Sep 10, 2006

Not an option, unless you want to send me a free demon carb.

I just want recommendations on what the problem is or might be, not what carb I should be running. Everybody will have their opinion about what carb to run but none of that really helps me at the moment.

66newbie · Sep 10, 2006

tweet66 said:
I have a 525 cfm Demon carb that I'm selling for $200 + shipping if your interested. I went with a 351 and bigger cam so I switched to a 750 Holley. Only used for 4 months on my 302.

thanks tweet but no thanks. I see no reason to spend more money at this point. That carb I have was rebuilt by Tomco. I think I just need to adjust the choke and I will be fine.

BornInAFord · Sep 10, 2006

Autolites are generally reguarded as one of the better carburetors out there in terms of reliability and simplicity. Rather than run out and get another carb (which could give you the same results since you may have other issues besides the carburetor to deal with), talk to us about what combo you have and why you rebuilt the carburetor since that will help us trouble-shoot... My gut feeling is that your problem is vacuum and perhaps timing related.

A few questions: Is your fuel system new (i.e. new filter, working fuel pump and new "sock" in the fuel tank sending unit)? Have you checked the carburetor base for warping? Have you tried to set the choke more lean(there should be a black plastic plate on the choke you loosen and turn counter-clockwise to lean out the choke)? Do you have binding in either the linkage or is the choke linkage screwed too far down? Do you have an Edelbrock Performer manifold and, if so, are you using a spacer plate between the manifold and the carburetor (as well as the requisite gaskets) to stop vacuum leaks there?

As far as the choke, it should be slightly open when starting (it never closes all the way), but should open within a few minutes of starting. It should move freely with no binding, too.

Good luck on the trouble-shooting. Like I say, although there are many other good carburetors out there and some that make more power or are more tuneable, the 4100 is a great caburetor. Mine has over 400,000 miles on it and after a rebuild or two still works well and gets 18/25MPG city/highway with my combo. I have a warmed up 5.0L HO with a Performer intake (with stock PVC spacer and with a 1/8" Moroso spacer to eliminate leaks), a T5 and 3.00:1 rear.

Daniel

66newbie said:
I have a rebuilt Autolite 4 barrel. I look at the choke and it's slightly open. I never adjust the screws at all.

I put the carb on but I realize that my heat tube coming off the exhaust manifold is rusted and broke off.

I get the car to start but it idles rough, I pull the throttle linkage and the choke plate snaps completely closed and the idle goes up (a little to fast of an idle)

I pull the throttle linkage back again and the choke plate resets to an opening of 1/4" (estimate) and it idles rough.

I can repeat the above last two steps.

I let it idle roughly for a few minutes and it dies completely.

I can't get it to restart until I let it sit for a while.

I have checked for vacuum leaks and I am pretty sure it's air tight.

How big of a difference does the heat tube make ? I have the heater hose next to the choke like it's suppose to be.

Is there a hose to release the air coming up from the heat tube ? Cause I don't see a connection for that.

What is causing the choke plate to do that ?

66newbie · Sep 11, 2006

BornInAFord said:
Autolites are generally reguarded as one of the better carburetors out there in terms of reliability and simplicity. Rather than run out and get another carb (which could give you the same results since you may have other issues besides the carburetor to deal with), talk to us about what combo you have and why you rebuilt the carburetor since that will help us trouble-shoot... My gut feeling is that your problem is vacuum and perhaps timing related.

A few questions: Is your fuel system new (i.e. new filter, working fuel pump and new "sock" in the fuel tank sending unit)? Have you checked the carburetor base for warping? Have you tried to set the choke more lean(there should be a black plastic plate on the choke you loosen and turn counter-clockwise to lean out the choke)? Do you have binding in either the linkage or is the choke linkage screwed too far down? Do you have an Edelbrock Performer manifold and, if so, are you using a spacer plate between the manifold and the carburetor (as well as the requisite gaskets) to stop vacuum leaks there?

As far as the choke, it should be slightly open when starting (it never closes all the way), but should open within a few minutes of starting. It should move freely with no binding, too.

Good luck on the trouble-shooting. Like I say, although there are many other good carburetors out there and some that make more power or are more tuneable, the 4100 is a great caburetor. Mine has over 400,000 miles on it and after a rebuild or two still works well and gets 18/25MPG city/highway with my combo. I have a warmed up 5.0L HO with a Performer intake (with stock PVC spacer and with a 1/8" Moroso spacer to eliminate leaks), a T5 and 3.00:1 rear.

Daniel

Daniel,
I agree with you, it was someone else who suggested just dropping it because it doesn't work. The reason I bought the rebuilt carb in the first place was because I have heard nothing but good things about these carbs once you get them "set". The original carb was a two barrel and it ran ok. I want to upgrade to the 4 barrel and an AOD for better driveability and mileage, so thus the switch.

I have a stock cast iron 4 barrel intake with a spacer. I checked for vacuum leaks around the base of the spacer and the base of the carb. My vacuum gauge is showing good and steady. Fuel pump is the same that I was running on my two barrel.

I will try to lean out the choke. I am trying to figure out why it's snapping shut when I pull the throttle back and then resets itself.

5.0ina66 · Sep 11, 2006

whosgt said:
i would suggest buying a road demon and being done with the problem all together. you are going to have nothing but problems with this carb from now on.

SOmeone is sofa king we tall did Nothin' wrong with 4100s

mitchcj1 · Sep 11, 2006

I have a 2 brl on a 351c, but my heater tube is rusted off too. I dont really have any problems with the idle. I got anew tube but cant get the old tip out, so its just resting against it for now. Point is, its not affecting idle that I can tell.

66newbie · Sep 11, 2006

I will work on the carb this evening. I think it's flooding out. I will try leaning it out a little and see how that works. My biggest concern is that the choke plate closes completely when I pull the throttle linkage.

66moneypit · Sep 11, 2006

How is it rusted off on the manifold ? Is it possible to get a tube inside the broken off tube ? You should be able to make that work, you'd just have to get a fitting to hook up to the carb that also works with your tubing. You could also go with the regular tubing from the carb down to the manifold and put a smaller diameter tube on the end just to fit inside the broken off piece.

302 coupe · Sep 11, 2006

you could disable the choke all together (temporarily) and see if it runs better, of course that would be after you put in new spark plugs since your old ones are now fouled.....

The heat tube is what caues the choke to open up as the engines warms. If the heat tube is disconnected, the choke never opens, which results in an overly rich mixture which fouls the plugs and causes it to shut down. The carb is probably ok. You need to have the heat hooked up for the choke to work properly though. There are repair kits (copper tubing and some fittings)in the "HELP" section at most chain stores. Good luck.

66newbie · Sep 11, 2006

302 coupe said:
you could disable the choke all together (temporarily) and see if it runs better, of course that would be after you put in new spark plugs since your old ones are now fouled.....

The heat tube is what caues the choke to open up as the engines warms. If the heat tube is disconnected, the choke never opens, which results in an overly rich mixture which fouls the plugs and causes it to shut down. The carb is probably ok. You need to have the heat hooked up for the choke to work properly though. There are repair kits (copper tubing and some fittings)in the "HELP" section at most chain stores. Good luck.

How do I disable the choke ? Or what's the best way of doing that ?

302 coupe · Sep 11, 2006

look at the linkage, you should be able to find a little clip on there that you can remove to disengage the linkage. Or, just loosen the three screws that hold on the black housing, and rotate the cover until the choke is open. I'd be incredibly suprised if the remanufactured carb didn't come with directions.

Autolite carb frustrations

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