We have 2001 Tahoe with the 5.3 and 130k miles on it. I want to go ahead and buy a used engine so that when engine gives(it has a knock on cold start-up), I am not out several thousand dollars buying a brand new one on short notice. What engine would you guys suggest? I was thinking a 6.0 just for a little extra grunt (I drive a chipped Duramax and the Hoe feels like a turd compared). Fuel economy is only around 14 to and from work, so a 6.0 shouldn't be that much worse I'm thinking.

 

all lsx engines have a tick/knock when its cold, the 6.0 is a great motor and a direct replacement

 

If you build this motor and just put it on a tire in the back corner of the garage waiting for your current 5.3L to take a , the new motor will collect quite a bit of dust. I have many friends and family members with over 150k miles on their 5.3L's, some have broken into the 230k mile range already. I think you'll be waiting awhile.

If anything, just build up a new motor on the side and swap one in once you've completed the build. A 5.3L bored over to a 5.7L is a good candidate if you want a fresh start with a perfect block, new pistons and a balanced rotating assembly. With a good tune I'll bet heavily that 18-20mpg is still possible if you don't go hog wild with the power. Hell, my 2002 Suburban 5.3L was getting 18mpg or so on the highway, untuned. Sounds like your Tahoe could use a tune as well.

 

Tuned up and a tune wouldn't hurt a bit. I hope this engine lasts for at least another 40-50k. A few years ago i had the chance to buy a wrecked 2500 burban for 2200, trans engine and all, just didn't have the funds at the time.

 

Ive got 143k and its goin strong, Im not worried about the engine, the tranny is a different story, works great and havent had any problems, but I know its inevitable... I would do what inchup said, get what you want and once its built up go ahead an replace it and scrap your older motor for a couple hundred bucks