WTB: Autolite 4100 "M" primary booster cluster

C6ZZKGT · August 5, 2020 at 3:05 AM Official Post

Quote from rtate

my 1.12 carb currently has "KD" primary and "BA" secondary boosters

Carb was rebuilt by Pony Carbs several years ago.

Your "KD" booster is for a 1966 full size Ford with a 390.

-Fred-

rtate · August 5, 2020 at 2:48 PM

That makes sense as I think that is what the carb is from.

it is a C5AF-H

Would the KD booster be to big for my 289 ?

The reason this journey started is because of a "flat spot" during acceleration around 1000 to 1500 rpm.

I was thinking that I was not getting enough fuel during "transition" from the idle circuit to the main circuit.

C6ZZKGT · August 5, 2020 at 4:50 PM Official Post

Quote from rtate

That makes sense as I think that is what the carb is from.

it is a C5AF-H

Would the KD booster be to big for my 289 ?

The reason this journey started is because of a "flat spot" during acceleration around 1000 to 1500 rpm.

I was thinking that I was not getting enough fuel during "transition" from the idle circuit to the main circuit.

I would begin by checking the bushing size that I mentioned to a #54 drill bit as that controls the amount of fuel to the booster. It is also possible that the booster is warped and not totally sealing to the carb body. A second gasket can sometimes be a cure for that issue.

-Fred-

rtate · August 5, 2020 at 11:10 PM

Thanks Fred, I'll check that out for sure !

66GT289 · August 26, 2020 at 10:28 PM

The "K" booster was also used on the 1962 221 carburetor. (C2OE-N & C2OE-R)

I've used those more than once on 1.12 carbs on small blocks. It does fix the unresponsive idle mixture screw issues, is a legitimate "replaced by" booster in the hipo carburetor lineage and provides correct performance from that carb.

I've never checked the bushing size though.....

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