poppin my post cherry! 6.2 is Garbage with a CAP G! i work on them all day.. im a military tech. glow plugs break often, no power, blow head gaskets, crack journal caps. i hate them. the 6.5 got some upgrades, at least the turbo version did, but still not a desired motor IMO. if you want some power out of it you wont get 20mpg either. you have to change the injection pump timing to get some power but with 175k on that motor it wont hang with it. i would trade but only to put a cummins in the truck. or just buy it out right and drop a tbi small block into it or something. they are cheap and plentiful.
I don't swear by them--I swear by mine.
Mine is a 1988 former Forest Service truck I bought in 2004 with 46,000 miles on it. It's at 115,000 now, 9 years later. I put a Banks turbo and a Gear Vendors splitter/overdrive on it when I first got it. In 9 years I replaced the waterpump, the alternator, the radiator and the brake master cylinder. I also put a new o-ring on the throttle shaft of the injection pump.
I want to help you hack on these things because I am not a Chevy lover, but I can't help you do it. Compared to my Powerstroke van this truck is much quicker, handles much better, pulls heavy loads much better and I think for the price of a single Powerstroke injector, I could buy a replacement motor for the 6.2.
I was in the marines for 10 years in the 80s and 90s and we had Hummers. Ours worked fine. When I bought my pickup in '04 my neighbor, a former Guardsman motor-t mech, promised me I would need an injection pump within a year. That was 9 years ago. Guards hummers sit most of the time, or they did before we started using the guard as regular army. I think that is the root of the problem. My truck has been a daily driver most of the time.
You should know that my trailer weighs 6,000# empty. It's a 24' WW-Trailers tri-axle gooseneck with a 12" frame. My 6.2 pulls 12# of boost has no problem with a track loader and my little backhoe on it. I have enough money to buy a new whatever everyone says is best. What I have still works and that's why I still have it.
I suspect my block is cracked. It doesn't mean anything. It's a hard pulling engine and I can get 23mpg empty if I hold it to 60mph. It gets 18mpg if I go 70-75 on the interstate. The cracks found are not failures, they are found during inspection. My truck is 25 years-old and I have zero concerns about it. In fact, it's TH400 is the most reliable piece of machinery I own. I'd be the world's biggest idiot to get rid of this truck.
I mean, what do you want me to say? I have a Powerstroke van rated at 210hp 425ft# and it's no match for my Banks 6.2. Banks rated their 6,2 at 207hp and 396ft# at the rear wheel--I called them to confirm this was the chassis dyno rating.
You would replace my motor with a 350? I had a 350 before I switched to a 6.2. I switched to a 6.2 because of a lovely running 350. I enjoyed 8 mpg average towing a little 6,000# load. I got 16 mpg with the same load and the 6.2. The 350 lived in 3rd gear on hills, the turbo'd 6.2 never downshifts, even with 12,000# on it. The 350 was slow in the 2500 4x4 I had it in. I have a friend with a 7.4 in a 2000 2500 4x4 and that truck feels a lot closer to what my Banks 6.2 feels like. But I get a lot better mileage.
So, yeah, the 6.2 is a piece of shit. It was designed and built by those idiots at Detroit Diesel who don't know which end of a crankshaft is up by people in Dayton, Ohio who don't know which end of their state is up. I would shy away.