Autolite 4100 4V question

john_simms

New Member
Oct 21, 2010
3
0
0
Edwardsville, IL
Hello Folks,

Newbie here to this forum so bear with me. I have a 64 1/2 with the code "D" 289 and 4 barrel carburator. With the engine off and the throttle held open, the secondary actuator lever can then be manually moved. My question is, should there be fuel pumping into the secondary venturies when I do this like occurs on the primaries when manually moving the throttle actuator? I'm not totally convinced that my secondaries are opening and if they are, they are delivering fuel. I saw a suggestion on one forum to fix a piece of string or tape to the secondary actuator, go for a test drive, floor the throttle and see if the tape or string is pulled loose or broken. My secondaries are NOT pumping fuel onto the throttle plates (engine off) when manually moving the seconary actuator rod, but I don't know if they should be.

Thanks in advance for the help.

John
 
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Az Pete

10 Year Member
Mar 30, 2005
711
18
49
Panama City, Fl.
There is not any accelerator pump on the rear two venturies. It should draw fuel thru vacuum produced when open and running.

Under normal conditions, just reving the engine with no load will not get them to open.

What I have done in the past is locate the linkage that has to move when they open. I put a small amount of grease on the slide portion and drive the car. Upon returning, I look for a change in the grease. Some have used a paper clip but I don't like the idea of it getting mixed up with the linkage and causing problems.
 

john_simms

New Member
Oct 21, 2010
3
0
0
Edwardsville, IL
Thanks AZ Pete for the reply. I should have thought to phrase the question regarding an accelerator pump for the secondaries. I'll try the grease trick and see what I find out.

Take care.

John
 

horseballz

10 Year Member
Sep 30, 2009
820
19
39
Las Vegas, NV
A 4100, properly jetted and setup/tweaked/tuned for a specific application will never give you a seat of the pants "kick" that some other carbs may give upon opening the secondaries, but WILL give excellent smooth performance with reasonable fuel mileage (if you keep tour foot out of the secondaries:rlaugh:) and great driveability. The lack of a "kick" is a good thing, as the "kick" is actually a slight bog before more acceleration. There are ways to get the secondaries to open earlier (I'm not sure what needs to be done). There is also a mod to make the secondaries mechanically operated, but seeing as there is no accelerator pump on the secondaries, I don't really see the point/advantage. If your secondaries don't open, upon testing, there is ether a plugged/clogged vacuum passage or the diaphragm on the rear of the carb is bad.
HTH,
Gene
 

rbohm

SN Certified Technician
Apr 12, 2002
6,669
540
204
61
tucson,az
like horseballz said, you wont feel the secondaries opening, but you will hear them. listen for a hissing sound as the rpms climb under load.
 
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