Abysmal Mileage...

[Frank]

Looking for carb adjustments to provide better mileage for Sluggo. I rebuilt the carb (MC4150) a few months ago and it ran, but poorly. My mechanic sent out out to a carb guy he knows who corrected my freshman errors. Got it back and it ran fine and still does but I'm down to 7MPG .

I know I can do better and it did before my attempt to rebuilt the carb. I used to enjoy 11-12mpg. The thing runs fine but I'm going to admit my newbie-ness and plead for guidance on what to turn, when to turn it and which way to turn it.

Thanks...



Frank

[Billygoat]

sounds like a bad power valve, and I have seen them bad out of the package, so don't figure a rebuild would have fixed it.
IIRC Ristow had a link to a holley power valve that would fit, and are new vs ones that have been sitting in rebuild kits for who know how long.

[svining]

Still around 13+ MPG

My 82' with 2:73 rear end and rebuilt 2150 is still getting 13.25 to 14.25 MPG depending on speed and stop and start. Its a bit doggy but gets me there happily. Don't forget...no smog gear either, its Tennessee after all!

sounds like a bad power valve, and I have seen them bad out of the package, so don't figure a rebuild would have fixed it.
IIRC Ristow had a link to a holley power valve that would fit, and are new vs ones that have been sitting in rebuild kits for who know how long.

[Rich88]

Looking for carb adjustments to provide better mileage for Sluggo. I rebuilt the carb (MC4150) a few months ago and it ran, but poorly. My mechanic sent out out to a carb guy he knows who corrected my freshman errors. Got it back and it ran fine and still does but I'm down to 7MPG .

I know I can do better and it did before my attempt to rebuilt the carb. I used to enjoy 11-12mpg. The thing runs fine but I'm going to admit my newbie-ness and plead for guidance on what to turn, when to turn it and which way to turn it.

Thanks...

Frank

Don't know if you really meant MC4150 or the stock MC2150. Either way, the only adjustments are choke, idle mixture & idle speed. If those are correct there are no more tweaking adjustments, and none of those will affect the mileage anyway. The only remaining factors affecting mileage is whether the power valve is leaking by or not, and the jet size. Too big = rich mixture.

Power valve leakage can be confirmed by pulling the vacuum line from the PV vacuum port to see if any gas comes out. Gas = leakage = poor MPG. No gas is good and put the hose back.

Further, you should check the plugs. Proper mixture should show light tan plugs. Brown or black = rich mixture.