Join Date: Nov 2000
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Re: Another motorcraft 2100
A 351 engine is 36% larger than a 258. If they both spin the same rpms, it will flow 36% more cfm's. A larger carburetor has a larger venturi size. Placed on a smaller engine it will flow less air than intended, and the result will be lower velocity of flow thru the venturi than intended by the designers. It is this lower velocity that will result in the bog and lack of response. It may meter the fuel mixture too rich, and you can correct that by re-jetting. But the main reason for the bog will be that it is simply too large of a venturi. The small version of the 2100 has a venturi that is about 1.08" in diameter at it's smallest point (ie where the hour glass shape is necked down to 1.08"). You can read this number off the drivers side of the float bowl, it's ina circle just behind the accell pump linkage.
On the other hand, give it a try. What have you got to lose? Maybe it will work great and you can tell us all about it. If it does fail to live up to your expectations, you can keep searching for a 1.08 and swap it out when you find it.
84 CJ7, 258, HEI, M/C 2100 carb, 5 inch lift, RS9000's, 33x12.5 BFG M/T's, Lockright, full cage & belts, Xenon flares, AMC 20 1pc axles, GM dual diaphragm brake booster