Throwing ideas around - LS swapped Tahoe, built for mpg

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0xDEADBEEF

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As a previous V6 owner. There wasn’t a V6 LS(though that would have been awesome). It was a great engine, but it couldn’t tow anything. Made decent low end torque, hated a trailer, I also had the 5spd and never got better than 16mpg. I’d get the Tahoe, do an exhaust, high flow air filter, maybe a black bear tune.

This is why I don't like the fabled torque monster low-end power making engines of years past. The LS might be reving higher, but it gets up the hills better because it makes more horsepower.
 

HeavyAsAChevy

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Heck. If you want reliability, decent power and gas mileage. Swap in a 1uz-fe like my Lexus has. Or a 2 or 3uz-fe. All are V8’s. Otherwise just leave the 350.
 

Alteca

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I think a L20 4.8/6l90 would be a perfect swap for you, cheap, reliable(no afm or dod) and good on gas while still having decent power when needed.
Edit: also the 6l90s deep first gear allows you to run a rear gear such as a 3.08 while still having decent off the line performance(not that off the line performance would matter much in a family car)
 

OutlawDrifter

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Heck. If you want reliability, decent power and gas mileage. Swap in a 1uz-fe like my Lexus has. Or a 2 or 3uz-fe. All are V8’s. Otherwise just leave the 350.

I would agree with reliability and depending on which of the 3, decent power...but not gas mileage. I daily drive a Tundra powered 2UZ in prime condition, and it isn't anything to write home about fuel economy wise, and I'm not lifted or on tall rubber.

OP give it a good tune-up, swap in the newer MPFI spider injector setup, stock size rubber (highway treads), and let it ride. You'll be money ahead!
 

Cadillac Bob

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So are you stuck on having a 400? Nothing wrong either way but they’re basically just as heavy as 4th gen GM full size SUV’s like 20-50lbs difference 400’s are lighter. So your not going to save a lot of weight since your looking to be comfortable on long 1600 mile trips. But if changing out gears and getting a 6-10 speed transmission would be imo be a good choice or like other guy said just change out gearing for real highway “mpg” and delete your drag that could be best simple solution and get you a set of lighter weight wheels with best mpg tire you can find? But if your driving long intervals you can save weight with 3/4 full tank helps also. But keep us updated
 

FLJoe

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I'd question the return on investment. My 96 4 door Tahoe, which I've owned since nearly new and put over 500,000 miles on, consistently gets 16 MPG per tank, with an even mix of highway and city. Mine is a 4WD, factory tow package, and has LT 265 tires that I run about 40 PSI. It's the original engine, never been apart, but well maintained and in good overall shape. My point is you should expect more with a 2WD truck, tall gears and a tight engine. Not sure it's worth the marginal gain you might get with a different engine.
 
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