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post #1 of (permalink) Old 09-03-2003, 11:00 AM Thread Starter
 
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MC2100 adjustment


Could anybody tell me what the adjustment settings are for the mixing screws on a MC2100 carb. Mine is running rich (black exhaust), and I'm set at approx. 3&1/4 turns out from the seats. I did the GM HEI dist. swap at the same time as the carb. swap and I'm running at 9 degrees BTDC on the timing. And one more thing, don't the mixture screws on the carb. turn in to run richer and out to run leaner, or is it vice versa? Thanks.
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post #2 of (permalink) Old 09-03-2003, 11:09 AM
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Re: MC2100 adjustment

Run them in all the way (not too tight or you'll score the seat & booger the needles). Then back them out to enrich the idle mixture (in to lean). I started at 2 turns out and ended up around 2.75 turns out... YMMV
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post #3 of (permalink) Old 09-03-2003, 11:36 AM
 
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Re: MC2100 adjustment

A vacuum gauge hooked up to manifold vacuum works well for setting the idle mixture. You want the leanest mixture that will maintain the highest possible vacuum reading. As stated previously, turning the screw OUT produces RICHER mixtures and IN produces LEANER mixtures. After the motor is fully warmed up and choke fully open, adjust the idle mixture screws 1/4 turn at a time, moving them both in or out at the same time. You should start from say 1 1/2 to 2 turns out from being bottomed. Turn them out till you find what the highest vacuum is you can acheive at idle, then turn them in till it just starts to drop off, then just enough out again to restore the peak value. You are trying to find the point at which you still have that highest vacuum reading, but you are acheiving it with the leanest mixture.

If your plugs are really carbon fouled you might want to wire brush or replace them first.

Also, any change in throttle stop setting will effect the vacuum reading as well. It should idle nicely at 600-700 rpms when fully warmed up. Also, consider retorquing the intake manifold bolts if you are working with an inline six. My end one's used to back off over time. I think this is a common occurance and leads to a vaccum leak in the furthest cyinder(s).
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post #4 of (permalink) Old 09-03-2003, 07:39 PM
 
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Re: MC2100 adjustment

There's also the setting on the accelerator pump (the linkage that goes from the front to the arm on the side). That will affect it when you stomp the gas. The lower the linkage is set, the less gas the accelerator pump sends. Move it down until you feel hesitation on acceleration, then move it back up one notch. Mine currently resides on the second from bottom notch.
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post #5 of (permalink) Old 09-04-2003, 11:00 AM Thread Starter
 
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Re: MC2100 adjustment


That's where mine is set at now also, but I'll move it down to the bottom and see what it does just fer gee whiz. I hadn't thought about the pump linkage. Thank's.
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post #6 of (permalink) Old 09-05-2003, 01:30 AM
 
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Re: MC2100 adjustment

Another thing that will cause it to run rich is a bad or too stiff of a power valve. Leve turned me onto this issue, and I slapped a new/lower one in my junk tonight and WOW it woke that thing up. See the info here:
Southern Jeeps

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post #7 of (permalink) Old 09-05-2003, 01:33 PM Thread Starter
 
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Re: MC2100 adjustment


Bluseman2a, I checked out the Southern Jeeps link and printed it out, and I'll plan on getting another power valve, 'cause when I rebuilt my junkyard carb., (picked from a mountain of'em in the back of a van, it looked to be the best one as far as being complete and clean) it didn't have a metal tag with the numbers on it, so I just guestimated an approx. year for a 304V8, (74' I think it was), and the power valve was to long that came in the carb. kit and I couldn't replace it, so I cleaned up the one in the carb. and used it. Thanks a lot.


82' CJ7, 258CID (MC2100 & HEI convers.), T5, D300, Flowmaster series 45 muff., 265/15's on the ground
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post #8 of (permalink) Old 09-05-2003, 03:28 PM
 
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Re: MC2100 adjustment

Herb

You said in your write-up that you used a standard Holley power valve..... How did that work out for you?

Im asking because I tried that route, but the holley power valve threads didnt extend far enough into my base for me to feel comfortable even snugging it down.

Just wondering if you encountered the same or if some bases are different.

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