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Old 01-21-2017, 10:15 AM
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RawhideClab's Avatar
Join Date: Nov 2013
Location: Floresville, TX
Posts: 348
Carburetor question

I know this is the CJ section but I figured y'all would have dealt with a lot more carbs than the guys in the YJ section. So here is goes.

Alrighty hold on for a lot of info before I get to my question.

'89 YJ that I swapped a GM 4.3/700r4/np231c drive train into. The donor was a '89 s10. I did a complete rebuild on the engine. When I first swapped it in I was running the TBI intake with a adapter to a 2bbl carb. I started with a 500 CFM Holley. Ran into some problems with not getting idle low enough but under acceleration carb was great. I have a air/fuel ratio gauge installed and those numbers looked good at idle 14:1 and under WOT 12.-13.5:1. How ever under cruising conditions (maintaining any speed 55mph or 70mph same thing) I would go dead lean 19:1 on my A/F gauge. Played with it some and decided that 500 CFM was just way to big. Bought a Ralley 2100 2bbl carb (motorcraft 2100 copy) and installed that. Same thing happened, I would go lean while cruising. At that point my thought process was that I had to have some sort of small vacuum leak at partial throttle. Didn't chase that problem down since I had a new Edelbrock performer 4bbl intake coming.

I got the new intake on this week and while the partial throttle problem is definitely better, I still go lean at partial throttle. Seems to be a smaller window, if that makes sense

Here are my a/f readings

Idle: 14:1 average

WOT: 12:1-13:1 depending on RPM

Idle speed in N is 800RPM in drive 650RPM.

When cruising I can feel a deference when I start rolling into the throttle when the primaries start really flowing. I'm talking about easing into the throttle not punching it.

So here is the question if you haven't already figured out what I am going to ask:

How do I adjust the partial throttle on a motorcraft 2100?

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1989 Base 2.5Low Output,
5SPD trans, 2" Body lift, 235/75R15 AT's
Fondly named by my wife: Latisha (in the spirit of the Dolly Parton's song "Jolene")
Do what you can where you are with what you have. ~ Theodore Roosevelt
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Old 01-23-2017, 11:14 AM   #2
KyleB1996's Avatar
Join Date: Jun 2013
Location: Grandville Michigan
Posts: 230
I have the motorcraft 2100 on an AMC 304 and I believe it is adjustable by a linkage in the float chamber. It has two positions on a linkage that goes from the throttle to the front of the float chamber. Not sure if placing that linkage in the next slot over would make a difference or not. I'm no carb expert but when I rebuild mine that seemed to change the fuel to air ratio.
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