The Stovebolt Site Forums The Shop Area Engine Shop 10 mpg??? Is that what to expect from a 235?

We do have a fairly low rear end. 4.11 or something like. And the truck, 62, weighs close to 4,000 pounds....

But 10 mpg still seems very poor for a six cylinder engine. Do I need to rebuild/swap carbs?

Thanks in advance.

That is what I've always expected my 50 3100 with a 1962 235 should get, yet after two tests, I'm getting around 17. Can't say what the heck I'm doing right.

That sounds much better....

Care to swap engines?



P.S. On a serious note, did the '62 engine bolt into your '50?

Your rear gears are limiting mileage. You can swap carbs, adjust timing/advance curve, mod the exhaust, and probably get about 3-5 mpg gain (without performance loss); or you can swap the ring and pinion and get about the same results (if not better).

I got 12 MPG with a 235 and a 4.57 rear end. 10 MPG with a 4.11 is low.

Are you sure that your speedometer is accurate ?

Are you sure your rear axle ratio is a 4.11? My 62 is a 3.90 and these were alot more common. Anyways i have a rebuilt 235 about 3500 miles on it now and i am getting 24 miles/per/gallon I just put in a S10 5 speed tranny and i figure i will be getting close to 30 miles/per/gallon now!! my tires are 225/70/15

JunkYardFrog,
The 62 engine came out of my '53 after my front Oak leveled it. I bought the '50, put both vehicles on stands and changed complete drivelines (engines, trannies, drivelines). So actually the rear end is not a '50 but a '53 but still 4:11's.

Craig

I also get @ 10mpg as well. My casting no. suggests that this 235 was birthed between 58-60'. The carb is the ol single Rockchester. I've got the 3 on a tree and don't exceed going slow all the time. I'm hoping that someone chimes in who understands what the hay is going on ans can lay it out in Asst. Wrench Fetcher terms. I also have a gasket leak on the fuel pump, but not enough to make a difference.

my friggin f*rd with its 302 and overdrive are getting 10 mpg. and my pickup has something like 3.23's in the rear. hopefully ill get alot more mileage out of it when it gets warmer.

but yea, my friend drives a 93 f*rd with a modded 351 and 4.10s, and during the spring he can sometimes pull off 17 mpg.

Its odd if youre getting that low of mileage with such a small engine

Drew

What are you guys crying about?! I drive my '54 3800 panel to work which is 50 to 60 miles round trip and endup putting 11 to 15 gal. of gas back in the tank to fill itup (18 gal tank). Oh yeah, I was running 235x16s and switched back to the orignal size tire,7.50 x 17's to try and get the ratio lower(better gas milage?) so I could go faster than 40? with this 5.14 rear end.

Tony'n Weatherford, Texas that is.

You guys driving easy and getting 10 MPG should look at your carbs. Old Rochester B's have been know to the power valve jet open at low speeds.It usually won't have black smoke rolling out, but rich enough to kill the fuel mileage.Our 45 2 ton with a 235 gets around 11-12 mpg, and it heavier and lower geared than a pick up.

Thanks Tony,

That sounds like a good suggestion.

Very interesting....

I never hear of that before, but I'm new to this.

How'd you do that? Is there some kind of adaptor required to bolt up that tranny?

Tailgate up or down? This can help, my '68 C-10 used to get 3-5 better MPG with the tailgate down.

Beyond that, I'd start looking at the carb and ignition system. Might be running way rich.

Everything else in good shape and adusted? Coil, condenser, points gap, spark plug gap, rotor, and wires...

-Boyo

JYF, Have you checked the air in your tires? Must be running with all four flat-LOL. You may consider putting in a three speed w/o (with overdrive).

Here is a link junkyard frog. To give ya the basic idea how much work is involved and stuff. http://www.stovebolt.com/techtips/t5tranny.htm

hmmm

Thanks. Very interesting....

But over my capabilities at this time. It sounds good though!

hahaha

Thanks a lot!!! Don't worry. They're only flat on one side.



I'm gonna start with the carb, but your mention of overdrive has me interested. The poor thing really has to work to stay up with traffic on the freeway. Was there a factory overdrive available? I'm not up to the amount of work required to put in a 5-speed.

Good point! I haven't checked it both ways. I'm surprised it could make that much difference.

I will have to check the mileage again. It seems to be better lately, but right now my son has the tailgate removed to sand off the rust. That could be the key.

Thanks for the tip!

My '50 with a 216 in it and 4.11 gears got 19mpg, even with two engines in the back driving on the freeway at 55 mph, making GVW about 4600. It really sounds like you need to set your carb and check your vacuum advance, timing, and point gap too. I found that the dwell angle and timing setting made a huge differance in how well my truck ran. If your vacuum or mechanical advance is broken you will get terrible gas milage. Ditto on the power valve. Ditto on the timing being wrong. I like to run a slightly wider than spec point gap for a hotter spark. It just requires re-setting a bit more often. I have a dual point distributor that the 261 is going to get. Also check for fuel leakage, that will really fool you!

Woohoo!

12 mpg!!!

Oly was right about putting air in the tires.

Hey Boyo,

You nailed that one. Got two more mpg with the tailgate down. Up from 10 to 12. That's a 20% improvement.

I'll hafta dig into the carb and ignition situation soon.

Thanks for all the ideas.

Frog said:

This is part of your problem right there. If your traffic is anything like around here then they are going 65mph plus. To make one of these old trucks go 65mph your rpm's become astronomical and your mileage space shuttle like.

Frog,

When I was running my '54 Chevy 3/4 ton, with 4.57 rear, and 235 w/ Rochester B, I was averaging about 12 mpg.

If I drove it faster than 50 mph, the mileage plummeted!

My '72 C-10 w/ 250/Rochester B and 3.73 (?)rear, seems to be doing about 16 mpg highway.

Again, if I drive faster then 60 mph, then I can watch the gas gauge visibly fall towards empty
(at 60 mph, the engine's roughly turning 3,000 rpm).

This has been my experience... with the '54, I always used to scratch my head when I'd look at the serial plate on the door pillar which was silver lettering on a blue background: at the top of the plate it said "Chevrolet- for economical transportation"....being a poor kid in high school at the time, 12 mpg didn't sound particularly economical to me !

hmmm

Okay. You convinced me. I'm gonna try another test and keep the speed between 50 and 55. But in advance I'm asking for special prayers. I'll be going 20 to 30 mph slower than some of the traffic on our freeways!

There is nothing like blasting at high rpm in the slow lane and then getting passed by a grey haired lady in a Buick.

How 'bout doin' 65mph in the "slow lane", (trying to keep out of the way of traffic, even though the posted limit is 55 mph), on a cold snowy morning w/ a dusting of snow on the highway (just enough to make it slick), and you still have people blasting by you doing 75, 80, plus...in their rice-rockets or uber-SUVs, yappin' on the cel phone, puttin on the make-up, etc, while you're there in the "slow" lane listening to that long-stroke bolt scream, wondering how much more it'll put up with....

And that's in a '72 C-10 !!!

Better-off taking "the milk route" (& stopping for ice cream along the way!)

(sigh)

Gotta keep those revs down to get any kind of respectible fuel "economy"...