OBS to LSx conversion

[Wtfan18]

lol is it bad that i have absolutely no idea what any of that means?

[hellfire_studios]

Is there any easier way to make it work? What did you do to get your wiring done?

[RedHeartbeat]

You can send it to NelsonPerformance and have them mod it for you or buy one of their 4 wire harnesses complete. You hook up power, switched power, ground and speedometer output and you're ready to rock and roll. I can't remember the pricing, PM Mellissa@Nelsonperformance and she'll answer that one. There not too much to making the stock harness work, just get a factory wiring diagram from the harness model you have and figure out what everything goes to. Grounds are very easy to distinguish, black with ring connecters to go under bolt heads. Powers are orange, switched power is pink, wire in the dark blue and dark green leads to relays to control the fans(the wires output a ground signal for the relay). The green/white wire is the speedometer. The white wire is the tachometer signal.

[locrzn]

Blake from 417 motorsports in springfield,mo is going to do the install. He builds his own harness. I'm just taking everything I have to him. You have given everyone on this forum a lot of valuable info. I thank you and from the reponses I see everyone else does also.

[Wtfan18]

You can send it to NelsonPerformance and have them mod it for you or buy one of their 4 wire harnesses complete. You hook up power, switched power, ground and speedometer output and you're ready to rock and roll. I can't remember the pricing, PM Mellissa@Nelsonperformance and she'll answer that one. There not too much to making the stock harness work, just get a factory wiring diagram from the harness model you have and figure out what everything goes to. Grounds are very easy to distinguish, black with ring connecters to go under bolt heads. Powers are orange, switched power is pink, wire in the dark blue and dark green leads to relays to control the fans(the wires output a ground signal for the relay). The green/white wire is the speedometer. The white wire is the tachometer signal.

its $450 to have your harness reworked from Nelson Performance which is the route im going. much easier for me to hook up 4 than connect wires that dont belong etc. or they can make you a whole new one for $650 i believe. Either way it will save you a lot of headaches and time. IMO sounds pretty simple to install as well.

[98 4X4 burban]

its $450 to have your harness reworked from Nelson Performance which is the route im going. much easier for me to hook up 4 than connect wires that dont belong etc. or they can make you a whole new one for $650 i believe. Either way it will save you a lot of headaches and time. IMO sounds pretty simple to install as well.

if i had to do it all over again i would have gone this route and let then re work my harness

[hellfire_studios]

I have the harness for the 5.3 and the ecu I just want to make sure that I understand as I know nothing about wiring. we are talking about the 5.3 harness when you are talking about reworking it. Does the nelson performance people chip ecms as well? And with this rework I can use the factory cluster?

Josh

[RedHeartbeat]

NP will flash a PCM to work for your application. Yes, they can rework your wiring harness to work in your vehicle. BTW, what is your vehicle since you don't have it listed in your signature/usercp.

[hellfire_studios]

98 Silverado. extended cab short bed. began life as a 4.3

It is in the process of being rebagged and body dropped right now. Motor is about to be set on the new frame. Frame has been box tubed from the fire wall back. And narrowed in the rear by about four inches.

sorry for the dumb questions I know you probably get sick of answering them. body and frame stuff I know, mechanical and wiring....I know nothing.

Josh

[RedHeartbeat]

Whats up RedHeartBeat, read this thread (OBS to LSx conversion) like 3+ times its great. Just had a few questions (haha im sure thats how it always starts). Im about to attempt a swap my 1998 chevy 1500 350 5.7 4x4 auto to a 5.3l 4l60e 4x4. Since its not gonna be an ls1 do i still need the high pressure fuel pump and lines? The wiring harness from nelson does that just plug into the stock computer? Some of the threads half different results with things like abs,cruse control and a/c what the best route if attempting to preserve the luxuries? (a/c my biggest concern cause i live in phoenix) Thanks for any help with these ?'s Brian

There are many solutions to your conversion. For the fuel pump, use your existing pump and lines and adapt them accordingly. The fuel rail on your donor engine will mandate how to make the connections. If you have a single line fuel rail the Corvette filter is the way to do it. If it has a return line then you can use both of the original lines. The Nelson harness will supplement the factory original harness, you graft it into the 5.7 harness leaving the stock unit in place. Check your PCM and see if the last three numbers on it are 411. If so let Allen know and he'll send you the best tune he can for that PCM. If you're going with the Nelson harness, call them and see what all they recommend for the PCM. Its very common to have two PCMs installed in a 1998 model truck conversion, the 98 and the LSx PCM. What you do is remove all the connections from the 98 engine and leave them in place, then you install the Nelson harness and graft them together. After you're finished you just cut all the loose wires out of the harness. Search the site for alternatives for maintaining your stock A/C unit. I myself use the Street and Performance high right side A/C kit using a Sanden 508 compresser. Their website is Welcome to Street and Performance and they have some quality part though the prices are at a premium since they deal with street rodders. Cruise control, I don't have it. ABS is possible by leaving the stock PCM in place and you tie the speedometer wiring to both PCMs.