What'd I get myself Into?! LS1 Into 4.3 Sierra

I know its not difficult but in my particular case i bought a ls1 longblock and its proving to be quite the headache. I just bought it about a month ago, and havent done anything to it since. Im stuck in line waiting for the machine shop to have some space to get her in and check the condition. Bought it from a guy locally who pulled it out of his Camaro SS after it had a sudden but brief loss of oil pressure. He said that it lost pressure for only a second or two, then gained it back. After that he drove straight home only to notice a slight knocking noise. He decided it was best to pull it and throw in his recently aquired performance motor. I bought it as a longblock after he took all the pulleys, pumps, and other goods off it.. So now im here with a LS1 Block, with 706 heads. Im planning to build it before i throw it into my 99 sierra. im planning on throwing a tsp 228r cam, kooks lt headers, tsp bored ls6 oil pump, Evans waterpump, Manley valvetrain, SLP Timing Chain Kit, Volant Intake, LS6 Intake, SLP underdrive/Harmonic Balancer Pulley, Federal Mogul Main, Cam, And Rod bearings, Thats about as far as my list goes, and im sure its gonna change this weekend. Im meeting up with some friends a few towns over who own a performance shop so they can help me out with my build. Enough of what im doing, my main reason for posting this thread is to see what all I will need to do the swap. I have heard that some things can switch over from the v6, i know ill be using the 4l60e from my truck. Ill be having it rebuilt before anything. I read that i can use the 5.3 Wiring harness and pcm, is that correct? I was planning on an lq4 swap until this ls1 came up for sale. I'm sure this thread has already been posted but i thought it'd be better to post my own thread since i have more of an in depth build.

you don't have more of an in depth build. It's still an ls swap in a 4.3 nbs.

for me its more in depth, im not just buying a running ls1, mine is a bare minimum longblock. im buying performance everything so its not just the normal ls1 swap (buying a running ls1 and throwing it into the truck) if i needed someone to tell me "you don't have more of an in depth build. It's still an ls swap in a 4.3 nbs." i wouldnt have posted. I thought forums were here for advice and finding out how things are done, not saying oh, your truck is the same as every other ls1 swap. i know im just dropping in an ls1 but where im from nobody has done that, So it is pretty in depth to me. Maybe somebody else can help me out.

http://www.ls1truck.com/forums/showthread.php?t=9345

It is the same though. Why do you think it's different?

you can use a wiring harness from either a 4.8,5.3,6.0 truck or a camaro just have to let your tuner know which one you use, you will also need a computer from the same donor, computer is the same I believe for either the car or truck (1220411) Wiring is different from car to truck which is why you have to let your tuner know which harness you have so he can choose the correct definition file for your setup.

Wrong. Have to use a harness from a truck.

See this is the help im talking about. I know its just an ls1 swap to a truck but for me its in depth because im basically building the motor from nothing. I'm gonna goto my buddies shop today and plan things out with him since he'll be tuning my truck once the motor is in.

Ok well the swap will be the same, if it's the motor build you're having an issue with you should have this in a different section.

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Originally Posted by sleeper1500

Wrong. Have to use a harness from a truck.

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Why is that you think a camaro harness, I can think of no reason you couldn't

me either since my 93 and 92 both have camaro harnesses in them. Just don't try to use a 98 model harness, they're wired all backwards, that is unless you have a 97-98 PCM already(one year only in the camaro and two years in the Vette).

Ok since the year of the truck wasn't stated, I'm going to assume it's a 99-06. You could very well make an F-Body harness work, but why? It'd be more expensive more hassle more pain in the ass than just going and getting a harness from a V8 truck of the same year. Now if the swap is 88-98 than you're doing a complete retrofit and having to start from scratch anyway so it doesn't really matter which harness was used. My harness came from an 05, and other than removing wires to duplicate a factory 5speed harness it's a direct plug in. Easy peasy lemon squeezy

What year is the truck? HAVE YOU READ ALL THE STICKIES?

First thread,its a 99, but being a 4.3 still not sure if the 4.8,5.3,6.0L harness would intertwine with the rest of the harness, but if so the truck harness would be harness of choice. I guess you need to search that a little, however if it won't than you get to start from scratch so as I said before either will work.

BB

there are quite a few 99s running around with the 5.7L Gen1 style engines from Mexico so its always advisable to ask which setup is in a 99 when posted on here. :)

Ok, Truck is a 99 Sierra RCSB 4.3, I am not sure what yr the ss was that the ls1 came out of, I'll have to ask my buddy who's car it came from. I know i need the wiring harness from a truck, and I hear you can use the v6 pcm if you have it reflashed but I'm not sure. Which mounts do i need, truck v8, f body, or custom??? To use my 4l60e from the v6 what do i need? I'm having it rebuilt so its not an issue, just need to know whats neccessary to use it on the ls1. I am sure i need efans can i use the ones off an fbody or do i need the ones from 03+ trucks. if i use the ones off a truck i think i need a 03+ radiator, right? the swap is going to take 4-6 months, its kinda a side project since the v6 isnt runnin so good these days.

READ THE STICKIES, THEY ARE THERE FOR A REASON! I just got done reading the first few lines of the link posted earlier and it answered most of your questions. /END THREAD

yeah, i saw that it is a sticky for 4.3nbs to v8, but in the thread it talks about a 4.8,5.3,6.0 swap, didnt know if an ls1 was a diff swap coming from a car to a truck.

They're all the same engine family.

Dude just buy the harness off E-bay they all over there for about $120 and depending on what yr engine you use might have change INJ plugs and maybe a few other things.

v8 swaps in the 99NBSs are a little goofier than the rest of the NBSs. read all the way through the stickies (yes, they apply to LS1s as well), and read my build thread. mine's a 99 with an 01 5.3 swap.


ps - the 03s had the same clutch fan & 28" radiator that the older ones used. the swap for half-tons was in 05