I currently have a decent Carter 2-BBL from a 1976 Dodge truck 318 on my 170. On a long highway trip, I hardly got to 14 or 15 MPG. It seems to be running pretty well, but in talking to my great-uncle who drove slants back when they were new thought I should be getting closer to 20. He seemed to think that the jets in my current carb might be too big.

Right now, I have the head shaved .020" and it's ported and polished, a Comp Cams 252, Clifford shorties into a true dual exhaust with an X-pipe.

I have a Carter 2-BBL lying around from an actual Super Six that I wasn't able to get the throttle shaft moving. My question is this - would it be worth it to try and get the jets out of the Super Six carb and put them in the working carb on my engine? Would the Super Six jets be smaller than what I have?

Truck carbs tend to be big and fat. If both BBDs are the same variety (low-top or high-top) you can give it a try; you'd want to swap the jets and the step-up rods and the step-up piston & spring. Jets and rods do not interchange between low and high top BBDs. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download. Pay particular attention to the BBD material.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks a ton, Dan!! I'll definitely study that BBD manual and give it a try in the next couple of days.

I'm quite sure that both carbs look about the same from the outside, so I'm very hopeful that the jets and the rods, piston, and spring will transfer to the working carb.

You might want to try adjusting the step up pivot bar that controls the metering rod step up before swapping out jets. I had an experience with a vehicle getting 14 MPG, and it jumped to 19 MPG with just this step up adjustment and a timing change.

Lou

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Home of Slant6-powered fun machines since 1988

Thanks, Lou. It seems that the metering piston is frozen on the Super Six carb. I briefly looked at the carb manual Dan referred me to, and I saw that the 318 carb lets the metering rod move a lot more than the Super Six carb.

Again, thanks a bunch for the help!

I think that the Super Six has smaller venturis or throttle blades, its been a while. On thing I noticed with my old 2 bbl six was that the later model (lean burn) 318s had the same sizing as the six carb but the older ones were larger.

So I checked the adjustment of the step-up pivot bar as per the directions in the manual that Dan directed to me. Lo and behold, WAY OUT of whack. Those metering rods must have been at least 1/8" too high. No wonder I'm doing terrible on gas.

I'll have to wait and see how it does now.

Probably a lot better now.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.