Another V8 question

[John Pasinski]

I have a '72 flatbed C30 w/ an overhauled 402BB & 4sp trans.
I get about 7mpg. It's all original including the rear end. I want to put a 283 or even a 6cyl in to improve the milage. The guys I talk to tell me it will be way underpowered and I won't improve the milage. But I see C30's for sale that have 6's in them from the factory. Who's correct? Do any of you have C30's w/ 6's in them? How are they pulling loads?

[clear]

I would imagine if you put a 6 cylinder in there that motor would have to work harder then the V8 so you wouldn't gain anything. If anything you should put a beefier motor so it doesn't have to work as hard.

[GRX]

Originally Posted by John Pasinski

But I see C30's for sale that have 6's in them from the factory. Who's correct? Do any of you have C30's w/ 6's in them? How are they pulling loads?

One word ... gearing.

Drive train efficiency determines fuel mileage not engine displacement. Everything - carb tuning, to gear ratios, to tire diameter.

[Longhorn Man]

You need to figure what gearing you have.
Off the top of my head, I can't remember if that would be a 4.10 or a 4.56 gear. if it is a dual rear wheel truck, it's a 5.13.
I would seriously consider getting a later model 14 bolt rear with a 3.73 or so gear ratio. The engine can pull plenty. And most likely, you aren't even hauling/pulling the major weight the truck was built for anyways.
A smaller engine would help, but not as much as better gearing. Regardless of the engine, you'll still be reving 3000+ RPMs on the road, and still getting passed by socker moms left and right.

[magwakeenercew2jh]

Originally Posted by Longhorn Man

You need to figure what gearing you have.
A smaller engine would help, but not as much as better gearing. Regardless of the engine, you'll still be reving 3000+ RPMs on the road, and still getting passed by socker moms left and right.

Right on. I had a '63 (maybe it was a '65) back in about '83. It was a half-ton stepper with a 4-speed granny 1st. I changed the carb, coil, distributor, plugs, and almost everything that "screwed" that was engine related.

On a good day, I got nine.

But it could climb mountains.