6 cyl MPG

[69ShortStep]

1969 C-10, stock 250, Rotchester 1 barrel, 3 speed, 3.07 rear, power steering.

Getting 13-14 mpg combined. I use it to commute which is mostly 70% highway.

I justed installed an HEI yesterday ( Thanks to Longhornman's and Shifty's FAQ threads on the subject ) and hope to squeeze out another 1 mpg.

Hope this helps.

[Fred T]

Dad had a new 64 with the 230, got about 15. I had a new 74 with the 250, barebones truck with 3.73 gears. It got about 15. I also had a hi-mile 80 van, 250 with a progressive 2 bbl which got 18 on a regular basis.

From my experience the best milage will come with better gears. Most of these 1/2 tons came with 3.73s. 3.07 was an option, but has the problems of clutch wear and can cause lower milage on the highway when the engine struggles to maintain speed. Gears in the 3.30 range are a better match. Another option is an overdrive tranny, manuals usually give you a .85 od gear, makes the 3.73 a 3.17 and keeps your first gear halfway low. The 700R4 auto is another option, but od is .70, final ratio becomes 2.61. Usable, but not the best for the six.

For the lowest dollar improvement go with the HEI distributor. They are starting to get hard to find at the junkyards. www.stoveboltengineco.com sells rebuilds for a decent price. If you call him, he can also give you some advice on calibrating the advance curve for better highway milage.

As for headers, a free flowing exhaust does not usually improve milage. It will increase top-end performance, which means you can put more fuel through the engine at high rpm.

[shifty]

Originally Posted by rio

what kind of mileage you'd get with that 3.07 rear end.

Took me a sec to get that at first, but when I did, I was ROFLMAO