witch engine would be better for a mpg build? Going in an early a body.

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Dave

1977 d-200 crew cab ex-army pickup wants it's /6 back
1962 Valiant 2 door, 170, three on the tree
1972 d-100 parts truck
80 volare wagon now a parts car

I vote for 170. I have a 64 Valiant in my yard with a very mild built 170, 9.5 CR built like a race motor, but for economy. It gets around 27-28 mpg, with a 3 speed stick.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

I've never owned a 170, but common sense says that 55 cubic inches less would be better on gas. My bone stock 225 in my dart gets around 18mpg, could be better if I could lay off the gas

Maybe, maybe not. Some cars with smaller engines require more foot-in-the-throttle time to deal with traffic, hills, et cetera, killing fuel economy. Still, a little less rotating mass and a little less fuel at idle can't hurt.

Tuning, weight, and driving style will make more difference.

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

That's very true. My Dad's 65' Falcon has a 170 and three speed on the tree, he always said that merging to the interstate was hell in rush hour.

I also remembered, Ted Shultz (hope I spelled his last name right) runs a 225 slant six with a one barrel holley, headers, street cam, and water methanol injection in his 74 swinger and gets 25+ mpg withouth overdrive. Of course, he only does that good on gas cause he runs high compression and 2.76 gears.