Autolite 4100 question

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Dec 6, 2012 | 12:07 PM

F-250 restorer

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From: Near Los Angeles

Autolite 4100 question

Anyone know if the screw in filter in the front of the carb reduces fuel psi coming into the carb?

I can't use the filter b/c it hits my v.cover. Now with two different 4100's I'm having probs with fuel flowing past the needle/seats. Needles are vitron. I've tried three sets. I've adjusted floats from top to bottom, with no effect.

Measured psi into carb at 4 or 4.5, can't remember which. That shouldn't be a problem.

Dec 6, 2012 | 03:59 PM

wyckedcombo17

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From: Suburbs of Chicago

It shouldn't if it's not plugged. If anything it only reduces volume. In my holley I took it out just in case it did get plugged, I run an inline filter now.

You're having an over pressure issue?

Dec 6, 2012 | 05:40 PM

Rusty_Old_F250

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From: Western Washington

Which needle and seat is leaking? Primary? When is it leaking? Idle? 1500, 2000, 2500 RPMs? All the time? EDIT: What's your fuel pressure at those RPMs? You could get a pressure regulator and install it and see if it helps.

Are you dead sure that the spring clip that holds down the float is in place and not damaged? That clip should snap down under the edge of the brass seat.

Are you sure the seat is in there straight and not cross threaded or crooked?

If the primary one leaks and the secondary one is fine, switch them. If it's an issue with the seats themselves, it should move.

Also, check out the diagrams in this link: autolite 4100 carburetor rebuild ? - THE H.A.M.B. Someone took the time to scan up several pages of the 1966 Comet, Falcon, Fairlane, and Mustang Shop Manual.

If you could get a couple pictures carb with the top plate off that might help.

Sam

Dec 6, 2012 | 07:58 PM

F-250 restorer

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Thanks for the replies. I've rebuilt many 4100's and never had this problem until I ran it w/o the oem screw in filter. I've checked and rechecked everything. Now it has happened on two 4100's, both w/o the filter. I'll bet the filter not only stops dirt, but also regulates/reduces psi to a level manageable or a level the carb was designed to run. Just a guess.

I know the seats are not in cross threaded, because I put them in with an air impact and torqued to 10 lbs. "Just kidding."

I think I will install a fitting on the oem filter and run it as an in line filter, and see if the problem magically disappears.

Anyone know where to get brass bushings for the throttle shaft?

Dec 6, 2012 | 08:12 PM

Rusty_Old_F250

Fleet Mechanic

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From: Western Washington

If I remember right those little filters just use a pipe thread and screw into the carb. I would just go to the hardware store and get a matching 90* pipe thread elbow and screw the filter into that.

Sam

Dec 6, 2012 | 08:12 PM

HIO Silver

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From: NorCal

Quote:

Originally Posted by F-250 restorer

I think I will install a fitting on the oem filter and run it as an in line filter, and see if the problem magically disappears.

Anyone know where to get brass bushings for the throttle shaft?

Nothing backs up facts like research.

Throttle shaft bushings.... start measuring: Carb Bushings

Yeah, you're welcome in advance.