Anyone ever rebuild a GenIII V8 with good results?
 

I recently acquired a 2002 Tahoe (LM7) with a fragged transfer case (there are literally chunks of the housing missing from it) and low oil pressure. My plan is to pull the engine, have my machine shop inspect the block and heads to make sure all is well, then install new bearings and rings and reassemble the engine. Once complete, I will swap the engine into... something fun. In my lifetime, I have rebuilt two engines that spun rod bearings on me (they were both turbo FWD Mopars) and everything turned out just fine--those engines both ran great for years afterward.

Lately, I've been watching tons of Sloppy Mechanics videos. On numerous occasions, Matt has said to stay away from any GenIII (or GenIV) engine with low oil pressure. He basically says if your GenIII engine develops low oil pressure, junk it and walk away. "I've never had good luck bringing one of these back from low oil pressure."

Question: is there something unique about the GenIII V8s that makes them die a permanent death if this type of disaster occurs? I've seen independent mechanics in YT videos who say low oil pressure is a common thing for GenIII engines, but they also say it's an easy fix (the oil pump pickup tube seal, I think?) and they don't sound all Chicken Little about fixing it. Is there something a newbie like me doesn't know, but I should?

Just wondering if I should cancel this project before I even start it.

A friend that's a SAM graduate rebuilt a battered Gen III LS1 into the 383 LS1 stroker that's in my 91 RS. No issues with the engine going on 3+ years and 10,000 miles.

Isn't part of the "sloppy mechanic" philosophy about doing max performance for the least cost, least amount of time and reusing the torque to yield head bolts over again? I wouldn't think folks that follow that idea would want to get entangled in any engine rebuild because between the parts & machine work to rebuild a Gen III LS1, it's probably less expensive to pick up a junkyard Gen IV engine in most cases these days.

If it's iron block then a rebuild isn't worth while price wise. A performance build is definitely the way to go. If it's an aluminum block it gets a bit tricky since the engine is worth more, but the rebuild is tricky to do (no overbore and slap it together on the thin liners) For aluminum if the liners are good then a performance build is the way to go. Basically if the bores are good build for more power and blow the doors off whatever crap youtubers think is cool.

The funny thing about the gen 3 is that they tend to have oil pressure sensor issues as they age. There's a chance some of these guys are throwing away perfect engines that just need a new sensor for the pressure gauge. Add to that the idea that the oil pump pickup o-ring may be due for a change and the number of perfectly good engines being thrown away increases more.

Most ridicules thing anyone ever stated about a engine. Ignorance is the only thing that is inherent in GenIII engines. Its not a small block chevy, you need to KNOW what you're doing. Most don't check the cam bearing clearances or pay attention to the frt and rear oil gallery requirements gaskets plugs etc. Lastly they try to use plastigauge as a mic and end up with a complete mess then blame the engine for crappy machine work. There is a list of things that need to be done if you expect trouble free performance from modern aluminum performance engines ITS NOT A SBCHEVY!

An engine is an engine. A good rebuild is a good rebuild. A poor rebuild is a poor rebuild.

There's nothing special about an LS that makes it harder to properly build, if anything it's one of the simplest engines ever produced.

I have also had better luck with used engines than I have rebuilds, but that's because often times people opt for low cost rebuilds.

Quite a few shops charge full price for crap parts and an interns labor. Rebuilt engines and transmissions are a gold mine for people who lack integrity.

KCS as usual posts correct good information. I helped a friend pull and rebuild his LS1 in a C5. He had the block tanked, cylinders honed (by a very reputable machine shop), new rings, bearings, GM rod bolts, and the usual stuff you replace on a heads and cam build. 2 maybe 3 HPDEs later the motor is running great not burning oil and very little found in the catch can.

True there are scammers everywhere but your chances of getting a high quality rebuild for low cost is pretty much zero. And there are quality builders out there, a lot of them. Just find a reputable one and spend the money.

And that is my philosophy as well. As one example, the 2.5L engine in my (former) turbo Caravan spun a bearing. This destroyed that individual rod and the crankshaft, but everything else was okay. I bought one new stock replacement rod, sourced a workable used crankshaft (it needed to be turned), then had my machinist order the appropriate bearings to fit. Once everything was properly cleaned and reassembled, that engine took years of abuse without complaint.

That depends on the total cost of the rebuild. Within reason, I think it can make sense. To wit:

This is precisely my plan, so long as the hardware (block, crank, rods) checks out okay.

I am certain you are correct. Fortunately, my machine shop has a proven track record of high quality work. There are cheaper machine shops in my area, and many which can get your stuff in and out with less waiting time, but there are none better IMO.

If I were going to take an iron 5.3 block to the machine shop the only good reason I can see for doing so would be to have it punched out to at least fit stock 3.9 ls1 pistons. Mill the stock heads a bit while you are there and you've got an honest 11:1cr 346ci. Depending on what it's going into or back into that may be worth doing over a slimy old 5.3 or 4.8 j/y cam swapped piece.

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Rebuilds just let all of the magic out.

If there is a reason to rebuild an engine it will be given to you, otherwise don't go looking for a problem.

I rebuilt one for my Tahoe, solid rust free but 180k and ticking. $500 JY engine, $700 O/H kit, $8-900 shop work, I opted for extras in sig. Now, it runs great, pulls harder and I, built an LS 5.3, 15k mi and counting. Now, what to put my old 5.3 in. If I went stock on my original it would have been around 1500. I do not trust JY motors to hop one up without rebuilding it, replace stock, probably. As for the Tahoe, sounds like it got abused. However, pull and inspect, if the mains are good and there's not a hole punched in it, build it for something. A few specialty tools and you can do it yourself, they are pretty simple.

I started the engine and it ran for perhaps 10 minutes until I gently drove it onto my trailer. By the time it was up there in place, it sounded like the engine was knocking.

Yep, I intend to disassemble it and check out the bearings. I fully expect to find significant wear, if not flat-out damage. But the block and oil pan are currently intact, so at least I have that going for me. I just need to wait and see what I find when I open it up.

Thanks, gang.

One of the best things ever written on LS1tech