I need a little help from LT1 guys.

I have built a Gen1 400 going into my '77 Vette. It has '89 heads. It's a converted roller motor with an LT4 Hot Cam.

Now, I'm set to buy a complete LT1 from a '94 Impala SS. I will only be needing the intake, harness, and computer.

Can someone point me in the direction of a good source for info, links, or pics to making this swap work?

I have a link to a company that will machine the dist hole and provide a spacer. They will also machine the water ports in the back, and anything else specified in there kit.

I guess I need tips and 'been there' comments from people with experience swapping in this intake system.

What computers are available, and what's best for the Vette? Being a 400 will I have to have a custom chip burned? What are my options there?

Thanks all for the help.

 

LT1 Swap Guide

LT1 Intake - LT1intake.com

You'll find links to other guys who've done it on these sites

 

I'll be sending my manifold to LT1Intake for the machine work.

I read through the other site, and while I found useful info, it still really only covers converting from TBI or TPI.

Keep the ideas and links coming.

Thanks.

 

if your running the 400 with the LT4 hotcam and LT1 intake, then just get a TPI computer and wiring harness. i'd like the 89 Mass air systems as its easier to tune. it should run ok on that 400 for now, but will need tuned for sure. thats a mild cam in a 400 so i think it will run ok for now. probly gonna want 24 lb injectors and abit higher fuel pressure. the MAF will help compensate some but it's just a starting point

 

Okay...great reply. Good info. Now, considering I have an LT1 harness and computer, should I still find a TPI computer? Also, will I want a 730 or 727?

 

yeah the LT1 computer and harness will not work. definately need to get a 350 TPI setup. i dont know exactly what number ecm the 89 MAF cars had, i thought the 730 ecm was for speed density but i could be wrong.

 

I think the harness can be MADE to work, and I have learned that maybe the ECM I need is the 7727.

 

The LT1 had optispark, which might be tricky, if not impossible to make compatible with a distributor. That would be at least one area where the wiring harness/ECMs differ.

 

That's true, but if I can cut off the optispark plug, trace the proper wires, and splice in a new set up pigtails I think it can be done. I've contacted a man who can make a custom harness for any vehicle and any application. Similar to what Painless would do but much better quality and much cheaper. I'll see what he has to say.

 

He cannot simply cut out the Opti and rewire. The PCM expects a 360PPR and 48PPR (IIRC) signal from the Opti to calculate engine position and injector/plug firing angle. I'm not saying it cannot be done, but it would be far simpler to use the older, batch-fire ECM and abandon the idea of fooling the PCM that there was an Opti in the house.

 

Okay...new info.

I found a guy in PA, that can do everything I need with the harness and computer. He will modify the harness to work with early HEI, and reprogram the chip to work with my 400, and all the things I want deleted. He's thinking the best program would be '94/'95 OBD1 LT4 cal. Does that sound right to anyone else? He only needs specs from me about the motor, the harness and computer, and it can all be done in a few days. Pricey, but worth it from what I hear as I'm using a 400 and that seems to be hard to program for.

 

i would hve never guessed you could use LT1 harness and chip to work with older small blocks...but oh well maybe it can be

LT1/LT4 doesnt matter on the chip..you still gotta correct it for 400 cu.in. and that hotcam.

 

Putting an MSD box in there might simplify the wiring.
The MSD wiring diagrams are online and possibly they have wiring that's common to both the TPI and LT1. Neither system uses a centrifugal or vacuum advance so they have that much in common already.

 

Yeah the guy I talked to was 100% percent sure that he could modify the chip to work with the 400 so long as I had the exact ML per cyl. and gave him a list of every component used. He said that was still a basic program. I'm excited.

 

good luck with that. let us know how it turns out for sure. i'd love to hear it

 

I will for sure...but it seems to me there is a lot more things to cover for this swap than just electrical. Can anyone help me with fuel system ideas? I know I'll need an external electric fuel pump, and I've been told a TPI car's pump will work fine. I will likely have to buy an aftermarket pump, that's a universal fit...but what do I use as the car to tell them? I need something that came with TPI stock. Should I say a Vette or a Camaro? Did any of the TPI cars have external pumps to begin with?

My Vette is already set up with an electric pump for the carb, so I have the wiring and relays already in place.

Thanks for all your help so far...it's much appreciated even though I know neither my '77 Vette or the donor motor came from a 3rd Gen. Sorry if I'm stepping on anyone's toes.