QuestionI have a 1979 DJ-5 258 engine....it has a carb. Auto Choke...Would like to change to 1bbl,manual choke..can you tell brand and where it can buy one to match my carb.
AnswerHi Jerry,
Carburetors are very specific to the engine they are bolted to. In order to put a different carb on your engine, you'll have to adjust the float, secondary metering rods, accelerator pump purge and primary jets just to name a few.
Seems to me that if you're going to go through all that work anyway, may as well just rebuild the 2bbl edition and save yourself the headache of purchasing jet-set after jet-set until you dial that single barrel carb to the engine it has to feed.
Also, FYI, if you think that a 1bbl carb is going to be more of a fuel miser than the 2bbl edition, you are mistaken, the 2bbl model will be more efficient on that 258cid engine. Why you ask? well, because the 258 you're putting it onto, stock, has a volumetric efficiency of 81%. The stock engine at 1000RPM's will use about 137.649 CFM of air at 81% efficiency. The single-barrel carb has a CFM rating of about 360. At around 2800RPM your 258 is using every bit of that 360CFM of available air. As you start to go over that mark, the engine still needs air but because the venturies are maxed-out, instead of drawing more air into the intake and subsequently into the cylinders, the carb feeds the engine more fuel through the main-metering circuit. The prime air/fuel ratio just went from 14.7:1 to about 8:1 because anything below that is plug-fouling range. The 2bbl on the other hand has a CFM rating of around 550 which is nearly perfect for a 258cid engine. The 3.750 inch bore and 3.895 inch stroke make this engine perfectly suited for making torque and at 4000RPM, this engines max horse-power range, the carb will be just under the needs of the engine which should be somewhere in the area of 500cfm
If all that just went right over your head, I apologize, but if you think you know something about carburetion and can't wrap yourself around the basic concept of what a carb does, then I'm not going to be of much assistance to you. If I got you wrong and you're trying to make a race jeep or installing a 1bbl to aid in rock climbing or something like that, trust me you'll still want to stick to that 2bbl carb over the 1bbl.
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Thanks for the question, I hope this information was helpful to you.
Fred
Knucklebusters Used Auto & Truck Parts, Inc.
www.knucklebusters.us
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