how bad are the 3.5/3.9 vvt's on gas? & heavier?

[no_doz]

ive been asking a lot of questions about building the crap out of a 3100 or 3400 because of the reliability & the availability of these engines cheap, but more than a few people have been telling me that the 3.5 would be a cheaper & much better alternative, and that got me wondering. how bad are the 3.5 vvt/3.9 vvt engines on gas? if i could find a cheap enough 3.9 id very much consider using one of those in my light car but i doubt theres any way i can get 30mpg highway driving nicely with a 3.9 vvt? i figure maybe with the 3.5 but not the 3.9-am i wrong? also how much more do these engines weigh than a typical 3100 or 3400?

[IsaacHayes]

Weigh? not a whole lot more. Maybe a little more with the VI and VVT. But were not talking maybe at most 40-50lbs tops overall. Probably not even that.

Mileage wouldn't be bad if you had it tuned well and had good gearing behind it. You could keep the revs low with the extra power and displacement.