LT1 swap info... rookie questions, just want to be sure

[coyote11]

I'm swapping in a 1995 Lt1 and T56 into my 1967 Firebird. I've heard some get the PCM reflashed, I've heard some say it's not needed. I am deleting all EGR, no need for it. I really don't care about codes it may throw. I did hear that if it throws a code the cooling fans will always stay on. I also know VATS is in there, but they make modules too. Is it just better to reflash it?

I'm also considering doing my own stand alone harness, I have every piece of wiring out of the donor car, and every sensor, I stripped it bare in my garage. I've heard, it's not so bad, and I've heard it can be a pain. Is it just miles ahead to buy a harness for the conversion?

I'm doing everything on a budget, trying to be successful at a modest pro touring car. I know budget is relative, but I can safely say a $400+ harness seems real spendy when I have a harness on my garage floor.

I'll take opinions and recommendations. Oh yeah, I know I have to get chevy engine frame mounts, and a custom T56 compatible tranny mount.

Thanks to all.

[GeoffP]

I put an LT1 T56 combo in my 68 Camaro last year. I used a 97 harness from a Firebird T56 car and a 94 PCM (they are pin compatible 94-97). Feel free to PM me any questions you might have. I can confirm that: 1. the fans will stay on constantly if the PCM sets any MAJOR codes. Minor codes don't cause the fans to run. Major codes would be stuff like O2's, MAF, or anything that would directly affect how the engine runs. Minor codes are things like A/C sensors getting bad readings and stuff like that (anything that does not affect how the engine runs). 2. you need to disable several items in the PCM to get it to run right.

The engine will not start if VATS is not disabled unless you're using a Passkey emulator (or an actual passkey setup). With VATS disabled, it should startup and run fine. I would disable VATS, EGR, and skip shift for sure.

If you're confident with the wiring, just cut up the harness you have and mate it to the original harness. You'll need at least a 4 circuit fuse block and a few relays: fuel pump, cooling fans, and I put a relay on the ignition circuit to feed it direct from the battery. DO NOT use the factory ignition circuit as your switched source - you will have all kinds of voltage problems and I have read on the Internet that the load will eventually melt the ignition switch since it was never designed to carry such a large load. I used the factory ignition circuit as the switched source for a PCM harness power supply relay. The relay is fed directly from the battery through a fuseable (sp?) link (in case of a short - no fire).

I learned the ignition circuit issue the hard way. My car would start and die over and over again. The relay fixed that problem quickly and easily.

I would invest in TunerCAT and a ALDL cable from Andrew Mattei (great guy!). You're only looking at a couple hundred (less than actually) to get these and then you'll have the ability to do what you need yourself. And it makes mail order PCM tunes a snap as you don't have to mail in your PCM. They will e-mail you the bin file where you can flash it in yourself.

I hope this helps - sorry it's so long. There's a lot to it, but if you take your time (patience is a big help with wiring), you can do it. As I said above, PM me if you've got other questions. I am glad to help.

87 Camaro IROC-Z LT1 4L60E 3.23
68 Camaro LT1 T56 4.10