Who is our resident LSswap expert here?

[Mains52]

I bought an 02 5.3 with 170k on it. I got the harness but no pcm. All I need to do is buy an 02 pcm and send it to be programmed right? Also I would like to know if I should do a full rebuild or if I can just put rings and bearings in just to put my mind at ease when dropping it in.
Thanks

[72blu]

I am by no means and expert but I do have a little first hand experience with LS swapping. yes you will have to send out your PCM to get refreshed so it suits your needs (rev limiter, etc etc..)

A rebuild can be a great idea especially if you have the aluminum block 5.3 as the iron cylinder sleeves tend to wear out. I have never rebuilt a LS motor before dropping it in. I bought a 2001 6.0L with over 300k on it for my 1986 C10 and I didn't even change the plugs when I dropped it in Still runs mint.

[Mains52]

Originally Posted by 72blu

I am by no means and expert but I do have a little first hand experience with LS swapping. yes you will have to send out your PCM to get refreshed so it suits your needs (rev limiter, etc etc..)

A rebuild can be a great idea especially if you have the aluminum block 5.3 as the iron cylinder sleeves tend to wear out. I have never rebuilt a LS motor before dropping it in. I bought a 2001 6.0L with over 300k on it for my 1986 C10 and I didn't even change the plugs when I dropped it in Still runs mint.

300k Holy Cow! Mine is an iron block with aluminum heads.I knew I'd have to send it out. I just wish there was a dude out here that would be willing to share info without acting like I'm an idiot. I exchanged about 14 emails with Brendan from LT1SWAP.COM and he helped me out but it seemed like he was a little short with his answers and he was irritated that I was asking him anything.

[mongocanfly]

There's a lot of knowledgeable people here with lots of differing opinions... your liable to get multiple answers to just about any question.. as far as a rebuild that's entirely up to you and the condition of the engine.. do a compression check first to see what you got..I had a 99 5.3 with 285000 on it that still had the factory spark plugs in it, still had good oil pressure and ran like new when I sold it..the only thing I ever did to that truck was a water pump and fuel pump..as stated any pcm you get will have to have a basic unlock and tune done and needs to be set up to your needs..then after you get it running I would highly recommend a dyno tune..

[mongocanfly]

You will need to rewire your stock harness unless its already been done or buy a aftermarket one..my factory harness was trashed so i bought a psi harness.
.don't be scared to ask any questions you got...somebody will answer them..

[BR3W CITY]

I'll just creep in from the corner....

The others have covered your initial questions (yes you need to have your PCM flashed, and yes its best to get the ECM that BEST matches what you have...IE find an 02 ECM from a v8/auto truck/van and it should be smooth sailing).

Wiring harness will happen with any swap. You can do your own (LT1swap.com for wiring info) or buy one pre-made which is my preference. Around $500-650 for a made harness. Look at your current harness and look at the big ECM plugs. Are they Red/Green or Blue/Green or?

I've pulled LS motors with 170k, not touched the bottom end and run them on nitrous. Actually ring gap is one of the biggest problems on LS motors (they break ring lands) and motors with age actually survive BETTER on spray because the ring gap and cylinder clearances open up a bit. If your really wanting a "fresh slate" then I would recommend:

Bottom end:
main bearings
cam bearings
switch your rod bolts to ARP
new/better oil pump and pickup (you'll probably want to swap the pan anyway for clearance).
new rings (READ LOTS ON RING GAPPING LS MOTORS!!!!!)
a master seal kit from Napa is like $140 and has all the timing cover/rear main stuff.

Top end:
Cam Kit if upgrading OR something like hotcam/z06 cam & spring upgrade OR just a new set of springs/seats. Pushrods can be reused if small/stock cam.
New Lifters GM LS7 design has superceded all old part #'s
Timing chain (I guess this is actually part of the bottom end/both)

Thats how I'd start a basic rebuild if I was looking to build a workhorse from an old stocker. Its like the LSx starter kit.

[mongocanfly]

Also don't forget bolts if you rebuild.(mains, heads, rods)..LS engines use torque to yield bolts (one and done)..be sure to replace em..like brew says get the arps..

[Heavymetl]

Don't touch the bottom end. Everyone is in a hurry to spend money there since that's what the old school always starts with in a build. I've been beating on a 156k junkyard 5.3 on 15psi of boost for 2 years and it still runs like stock. 170k is nothing....I wouldn't sweat that at all.

Take that bottom end money and buy aftermarket efi instead. Holley, ms3, etc. Much more simple to wire, tune, and work with.

[Mains52]

See I have thought about buying an aftermarket pcm system but with the amount of money that they are it seems crazy. I am doing a "blue collar/wife's watching the bank" build. She has never been around this stuff and doesn't understand what it takes to build a classic vehicle. This isn't going to be a show truck and I am not looking for crazy HP. I just want the efi and a good sounding cam and some gas mileage out of the engine. The guy I bought it from said it got a low oil pressure warning and the shop he took it to convinced him he needed a new engine instead of troubleshooting the oil pressure problem. That is where my OLD SCHOOL rebuild thoughts come into play. I would rather just re ring it and put new bearings in just for peace of mind but hell I have never rebuilt a new style engine and just don't know all the little quirks that go with them yet.

Thanks for all of the help.

[Willie Makeit]

if it's low oil pressure chances are its in the cam bearings and/or the oil pump. not the rings.

[Mains52]

Originally Posted by Willie Makeit

if it's low oil pressure chances are its in the cam bearings and/or the oil pump. not the rings.

Sweet ill check into those when I start tearing it down. Right now Im working on the chassis and getting my truck onto the s-10 frame.

Thanks

[Clyde65]

Many guys that reprogram the PCM's will sell you one without a trade in. I know that Nelson Performance in San Antonio Texas does this. Ask around!