MC2100 Swap, it aint gonna go -
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post #1 of 1 Old 03-02-2013, 11:05 AM Thread Starter
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1979 CJ7 
Join Date: Nov 2011
Location: kelowna
Posts: 201
MC2100 Swap, it aint gonna go

Hey guys
Finally got my carb adaptor in the mail yesterday, and I promptly removed the BBD and tossed the little devil as far as I could. Okay, not really, the BBD is still sitting on my bench. But I put the adapter on, and bolted up the junkyard carb I rebuilt. Fit like a glove. No throttle linkage yet, and I have the choke held open with a spring. So a friend and I crank and crank the engine until the float bowl fills, expecting the thing to roar to life. It does not.

So I pump the throttle twice, like I did every morning with the Carter. 2 squirts of fuel, and the thing roars to life and jumps up to around 3 grand, stays for a second, then nothing. Drops dead. We followed this pattern for 2 more hours, turning screws, trying to make the idle circuit, well, idle. I could then keep the Jeep running while staying on the throttle, giving it a squirt every second or so as it died. And I would like to note here that this carb gives me incredibly smooth top end. So after a while, my frind, daring man that he is, sticks the nozzle of the compressed air gun into the top of the carb. Right where the idle jets are, the two little brass or copper colored tubes that stick out at the top of the carb throat?Well, it fired, revved to 3 grand again, and he blew air right past those pick ups, and he could more or less make it idle with compressed air. Between 700 and 1200.

At this point, after 6 hours more or less of tuning and reassembling, it idles on it's own. But with the butterflies all the way closed and the mixture screws turned as far in as I can, it still only idles at around 1100, and it's not a very nice idle, either. And I can cover these brass "idle tubes", if that's what they are, with my fingers and the engine runs just the same. What am I missing here? The only other thing I can think of is that that little brass tube that drops from the top cover that leads to those tubes doesn't like to stay put. It has fallen off a few times, and we siliconed it back in. There's no vacuum leaks, the adaptor is sealed good and tight. I'm lost here

->'79 CJ7 (VIN Says it's a 5, wheelbase says otherwise), 6 inches of spring lift, awaiting an MC2100 on a teamrushed MSD'd 258

-->350 time. '95 block SBC, stroked to 383, dremeled heads and big 'ol intake, maybe a Holley 750 CFM, not sure yet

--->"Safety? Buy a Volvo. Never buy a CJ, or a Chrysler Jeep knock off, for safety, fuel mileage, reliability, handling, ride, comfort, aerodynamics, quietness, convience, stability, low maintenance cost, performance, or ease of use. The only reason to buy a CJ is because you are absolutely, incurably nuts." -OldTexas
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