I'm looking to do an ls1 swap next spring I've been doing a bit of reading on here and have noticed that most cars that get the swap are already Fi cars. my car came stock with a carb how much more custom work will I have to do to get my car to work with the efi that the ls1 comes with. I know you can get a painless wiring harness but my carb car dose not have a lot of the wires that a Fi car has. what options do I have would I better off switching over the ls1 to a carb set up thanks.

 

One of mine was orignially a carb car. Does your have an electric fuel pump from the factory? Mine had the mechanical pump on the engine as well as an electric "helper" pump in the tank. That helped since I already had the dash-side wiring I needed for the fuel pump. You will need to add an extra fuse block for the fuel injector fuses. My extra fuse block has fuses for AC, fuel injector bank 1, fuel injector bank 2, PCM, and HO2s.

There's really not THAT much of a difference between the TPI and carb cars when it comes to the wiring for the LS swap. I adapted a harness originally made for a carb car over to a car that originally had a TPI engine in it, and I only had to move 2 wires.

 

I know it has the fuel pump on the side of the engine but i don't know if it has a helper in the tank how would I wire up the extra fuse block

 

1987 and up should have the electric intank pump as well.

Jay

 

As far as the harness goes, talk to pocket. I got mine from him and it's absolutely amazing and not only a great price but far better quality than painless has. And he will answer all of your questions.

 

You could also just grab a harness from a 4th gen car firewall forward (drivers and pass side) and re pin the firewall connectors to match your car. That is what I am doing so that way I will be able to use the stock 4th gen and 3rd gen wiring schematics and diagrams for troubleshooting (and I have an obsession with 4th gen fuse blocks that are under the hood)

Looking at the schematics will allow you to at least see what wires you need to add or move or delete (or re-purpose)

 

The car is an 85 with the l69 and I have my eye on craigslist for a complete car so hopefully I'll get just about every thing I need

 

Harness changes are a non-issue, fueling changes are a non-issue

The basics of how to get it in the car are the same. Swapping the tank sender for an EFI sender will make life easier or use a 4th gen plastic tank. A simple stand alone harness is a cheaper alternative to a full plug and play harness and will come with the fuseblock you already need. You need to tie into the factory power/gauge points to finish it out

I never recommend putting a carb on a LSx engine. It was designed to be fuel injected, it works best fuel injected

 

Check out my build thread. My car was a non computer carb car as well. Built my own stand alone harness with help from the info on this site... Was rewarding to do it on my own, but I will be getting a harness from pocket simply for the looks (he builds them sleeker than I can).
For fuel, I used the 4th gen tank and pump, wiring for that was dirt simple. Used braided line and AN fittings up to the fuel rail.
I went with aftermarket gauges (Speedhut FTW) and that solved my fuel gauge readings.

 

Thanks a lot your thread really. helped me so for wireing you went through the harness cut the wires out of the pcm and harness and left the only ones you need and hooked it all up right.

 

I did two 3rd gen LS swaps, both originally carb'd cars, neither with in-tank electric pump. For one, I swapped in a 4th gen LS1 plastic tank and used a 3rd gen EFI fuel filter. For the other, I swapped in an EFI pickup in the carb tank and plumbed in a Vette filter-regulator.

If you have an L69, it's likely you have an in-tank electric pump. You should be able to swap in an EFI pump, but you may have to change fuel lines to handle the higher pressure. I used the carb hardlines, but took out all of the original rubber portions.

I didn't have the 4th gen chassis harness for one swap, so I found a swap fuse relay box and spliced it in. For the other, I had the 4th gen chassis harness, so I removed the unused circuits from the fuse/relay boxes and used them. I preferred the 4th gen stuff, although you could possibly reduce it down to one box if you were willing to repin the box you use (I was in too big of a hurry to get the car running to further consider that at the time).