Lt swap

[bazookatooth]

Hello all,
I've got a 72 blazer (I know this is a trucks forum but I figure it's more likely to have been done in a truck) that I would like to swap a '93-'97 era 5.7L lt motor into. Ls swaps are everywhere but all I'm looking for is fuel injection, and with tbi kits north of a grand and complete Lt motors and pcm's to be had for $750ish, it seems like more bang for the buck. I am fully anticipating that it will cost more than that in the end. I currently have a crate 350 that has been in the blazer since I bought it 13 or so years ago and a manual 4 speed transmission (a 5 speed will be included in this project as well). Setting the engine in and running fuel lines, hoses and what not seems pretty straight forward, it's the wiring that concerns me. Anybody done this swap? I visited the lt1 swap wiring guys website and it was very informative. What I don't get is how does the engine wireing harness tie into the blazers wiring harness and fuse box and what all do I need relays for and how do they tie in. I guess I'll need an electric fuel pump relay and cooling fan relay at the very least. I'd be interested in any insight at all, mechanical as well as electrical. I won't be running a/c. Is there a year that works best or is more reliable? I'm not trying to build a hot rod, I'm just tired of fighting carburators and losing, drivability and economy are what I'm hoping to accomplish. Oh, It's 4 wheel drive.
Thanks!

[Mike C]

I have several of the LT1 motors but haven’t completed my swap yet. I think they are a reasonable choice for what they cost anymore.

The easiest way to complete this swap IMO is to buy a complete running car. Then you get to remove all of the wiring, label it appropriately, and transfer it into your project.

Then sell the car to offset as much of the initial cost as possible. ‘96 is the best bet if I recall because of the computer and distributor.

[Bigdav160]

It's a pretty straight forward swap. If you're really adventurous you could machine the intake and put a distributor in eliminating the optispark.

Another option is to look at a megasquirt/microsquirt controller instead of the OEM computer.

I also used this Buss fuse/relay box (from eBay) to power up my EFI controller/AC compressor/fuel pump/front e-locker

[FL71C10]

I have an LT1 in my truck, and literally just got it running this weekend. Mine is a 1995 LT1 out of a Buick Roadmaster with a 4L60E automatic.

I had my original harness re-worked, and it is self contained in that you only need to hook it to a constant on 12V power source, a keyed on power source, and the ground. My harness came back with two fan relays, a fuel pump relay, and a relay for the TCC Brake Switch which is only needed for automatic transmissions.

My motor is a 1995 which is the last year of OBD1. So I cant get much useful info as far as codes, etc. 1996 was the first year of OBDII, as it had a crank position sensor (I believe that is the only physical difference in the motor itself). So 1996 or 1997 would be the most attractive years to get.

The Optispark distributor is the weak link in these motors. Good ones are expensive ($350 ish and up), and I'm not sure if they would hold up off road. They are mounted low on the motor and very susceptible to getting wet and ruined.

I kept the factory exhaust manifold from the donor car as it cleared my frame, but they are not real performance oriented.

I hate to say this, but you might be better off paying a little more up front and getting an LS motor. You could get a 4wd transmission as it came from the stock truck, and a whole lot more aftermarket support, and available parts such as headers, etc.

Here are a couple of pictures of mine installed.

[bazookatooth]

I think I'm gonna work the lt swap idea before ponying up for the ls. I don't know how concerned I am with aftermarket support being as horsepower and performance are not what I'm after here. I definately want to keep the manual transmission, it's the number one defense against car theft in this day and age and I do like to sort my own gears. I have a 1984 c30 crew cab with a ls in it if I want to hot rod something (not my build, bought that way). This self contained wiring harness? Is it a complete wiring harness for the whole truck or is it a engine harness you just have to supply power to? And I'd be interested in the details of ditching the opti spark. Some people hate it and others maintain it's great as long as you take care of it. As for buying a complete car...I think my wife would knee cap me if I bring home another complete vehicle, regardless of the reasoning. Thanks for the pictures, that fuse/relay unit looks pretty slick and that lt sitting in the truck looks sick! Looks like it has a much lower profile in the engine bay. I can just barely get my distributor cap off jammed into that recess in the firewall.

[bazookatooth]

Doing a little more research on the opti spark ignition it sounds like the distributor acts as a sensor of sorts supplying data to the pms for engine management purposes. How would that work machining the intake and installing a conventional distributor?

[truckster]

First, welcome to the board. There is a subforum specifically for engine and drivetrain, and you might get more answers there:

http://www.67-72chevytrucks.com/vboa...splay.php?f=24

I own an LT1 95 Z28. It's a fun car, but the LT1 is a dated platform and might not be quite what you're looking for. Look at the L31 Vortec - it's also a small block, with fuel injection from the factory, but it's easier to make power from and it doesn't have the optispark. Whatever GM genius thought putting a sensitive electronic distributor behind a water pump was a good idea should be sentenced to 1000 years of replacing them.

If you decide to go ahead with the LT1, check out the engine and drivetrain forum.