Quote:
Originally Posted by feller
did not read everything so sorry if i missed it but in a 4x4 can i expect to get better MPG's with an ls or lt swap? someone told me that in a 72 with a 355 and an edelbrock carb that would probably be as good as it gets, but i can not hardly belive that with 6.0's and 5.3 getting 15+ mpg in a new truck it has to get better than an old 355 ( mabey not)
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Absolutely it should do better in mileage.
I can tell you right now, my 72 blazer with it's 355, mild crane cam, performer rpm intake and 750 holley carb, 350 turbo, 3.07 gears and 33" tall tires. I get 13 mpg around town in stop and go. On the highway cruising at 70 mph at 2400 rpms, I get 16 mpg consistently. No overdrive, no fuel injection. Just a good tune and sensable driving.
With the 6.0 (364 cubes) and 4L60E I am certain I'll do even better. For starters, the factory tunes in the trucks are pretty lame, with single digit timing in the tables, etc....it's no wonder the new trucks aren't that great on mileage. All the emissions stuff to run through doesn't help much either.
Also there are a few tricks I can do in the tune to find 2-4 mpg in the part throttle areas. Doing the math,,cruising as 70 mph with this setup is only 16-1700 rpms (I'd like to see it a tad higher) and a gear change may be in order.
In any event, by the time I'm done, 20mpg or more highway isn't out of the question.
I tune my 4th gen camaros, and get 30+ mpg highway out of those with the LS1/6 speed combo.