The Stovebolt Site Forums The Shop Area Engine Shop 6 MPG ???

recently replaced my original 216 with a 235 from a 61 impala. Rebuilt the Rochester carb, and everything seems to be running fine, starts great drives out well, no complaints so I decided to check for gas milage since my gas gauge isn't working. I put the 235 into my 49 pickup, I still have original gas tank behind seat. It took 13.4 gallons to fill it up. now I am looking at 6 mpg, should gas milage be that bad? I was figuring maybe 10-12, but 6? I have noticed a slight leak, just enough to get your finger damp at the fuel pump fitting going from tank to fuel pump. Do you guys figure I will just have to live with this bad mpg or is there something I need to look at doing. By the way, I am using non-ethanol gas at 93% is that over-kill or necessary for the older engines. Sure would appreciate some help on this one. Thanks for any intrest an suggestions

Pull the spark plugs. If you are dumping unburned fuel (bad carb)out of the tail pipe, the plugs will be extremely sooty.

Hi Red

Can I ask what your rear end gearing might be?? Also what size tires are you running? I am curious as I am waist deep in a rebuild of one of these trucks and I am really wondering how bad these things are as far as mpg's go...I am hoping someone on here can shed some light on that terrible 6 mpg number...

If mine is that bad also...I will be selling mine..

MikeC

Thats not good. My 49 w/a 216 avg's 12 to 13 w/stock 4.11 gearing.

Someone may have changed out the main jet with something bigger (stock would be a 58) or perhaps the choke isn't opening up enough. Course no matter the cause you should be seeing black smoke and soot on the plugs if it]s running to rich.

A sbeen said check the plugs
good luck
Dave

It should get better mileage then that. The power valve on the model B roch. is hard to get correct. First make sure the hole in the bottom of the carb has a passage to the vacuum in the intake manifold. Make sure the power valve piston goes in the hole & knocks the ball off the seat. Make sure the vacuum advance is working. You should be able to see the dist turn at part throttle. Try advanceing the timing about 5 degrees above the spec.

Perhaps your fuel line leak is larger than you think and contributing to the poor mileage. Also, you say you are using non ethanol gas at 93%. If you mean 93 octane, I don't think that is necessarily good. These engines are low compression and may not burn that fuel very well. I don't know whether that would contribute to poor gas mileage but at least it is a waste of $$. Could you clarify what you meant by the type of gas?
For comparison, I get 12 mpg with my unloaded '50 COE with a later 1958 235, up and down mountain roads.
Kent

I usually get around 17 mpg, with a 235 and a Carter carburetor. Driveline is stock enclosed driveshaft with 16 inch tires, and 4.11 rear gear.
Don/RdsLessTaken

http://s1291.photobucket.com/user/RdLessTaken/library/

My stock 52 3100 got 15.0 MPG empty, and 15.0 MPG with a 3/4 ton pallet of potash in the bed.
You have something seriously wrong somewhere.
Tire diameter way smaller than stock?
Odometer?
Measurement of fuel used during your test is wrong?
Calculation error?
I am hoping its one of those. They are easier to "fix.
Carl

Check that carb base gasket first. If the hole in the bottom of the carb base is blocked off, that means the power valve is open all the time