inline 250 driveability

[BAGNDRAGIT]

so i have been fighting this truck since day one to be able to drive it, with one foot . and to get decent gas mileage.

a little info: 71 with a 250 backed by a turbo 350. Rochester Monojet, bone stock..

to start, i have rebuilt the carb after soaking. i have replaced the coil, plugs wires, points, condenser, cap rotor, all vac lines, vac advance, trans vac modulator, intake/exhaust gasket (still leaks a little, haven't put the new one on yet). also new negative cable new battery.

and i still cant seem to get her to run smooth, i just set the points gap (again) i have timed it ore than i wanted to and still having issues. sounds like its missing through the exhaust note (has a cherry bomb) but doesn't feel like it in the motor. (thinking the cherry bomb is toast) and at idle she stumbles, but if i richen it up (3 turns+) on the a/f screw she decent, but everyone behind me has burning eyeballs. i drive about 40 miles a day and it seems im putting 10-15 bucks in a day just to and from work. im stuck. how can i improve the mpg and driveabilty on this truck? its killing me and my bank account.

any tuning tips or any advice would be greatly appreciated.

[Ozark Tim]

I used to drive one daily.
My distributor was toast. Once I had a friend rebuild it so that it would keep a constant dwell and with a new vacuum advance working properly it ran smooth and got around 15-16 mpg.
Find someone who knows what they are doing with the original distributor rather than an autozone replacement and it should make a giant diff.
also the mechanical advance springs in it can be replaced with lighter tension springs to bring on advance sooner and that helped mine get a bit better perf.
Tim

[BIGBLU 72]

lots of times those 6 cyl truck have tow pig rear ends! swap out to some taller gears like a 3.42 or 3.08 should help it!

[Shaky]

A leak in the intake/exhaust gasket can make this happen. How many miles on it? Maybe it's time for a compression check?

[PanelDeland]

I'm going to suggest you bite the bullet and go to an HEI also.Much better and more consistent spark.

Beyond that,you may need to do a compression test and make sure you have a decent motor to try tuning.Usually a 250 will run till it's wore slap out but after 40 years.......
Sounds to me like a vacuum problem but you seem to have hit all the areas that I would suggest.However you can disconnect the vac line and suck on it to see if you're actually getting movement from it.The fact that you can richen it and have it run makes me wonder if you don't have an internal leak in the carb.
Does it have PB? If so there is a possibility that you have a vac leak in the booster.
Try blocking off the vac line to the booster and adjusting the idle.Or pull a vacuum on the booster and see if it holds.

Those are the things I wound up checking on mine.The vac advance wasn't working.I changed the vac in the dist and it got much better,but it really woke up when I put the HEI in.

[mr48chev]

As Shaky said, an intake gasket leak or vacuum leak could cause the engine to run lean and require the need to enrich the mixture that much. Along with checking the intake for leaks check the vacuum advance canister and hose to it for leaks. A bad advance mechanism will kill gas mileage right off the bat.

Definitely time for a compression check and maybe a leak down test.

First I would make sure that the compresson is up and even before proceeding with any type of tuneup work.

Then I would rebuild or have a good shop rebuild the carb and make sure that all the settings are correct on it.

then I'd hunt down an Hei out of a 75 or later 250 and install that along with the wires and correct plugs for an hei. Doing that on my V8 bumped up the mileage a bit and helped starting and driving to no end.

[Mike J]

mine has an HEI in it and seems to work pretty nice. Haven't really driven mine too much though. But the HEI seems like a good investment. Getting ready to put a new gastank in mine as soon as it gets here cause I keep getting junk in my carb. good luck brother.