Gen 3 like in my 68 is much easier as it has been done lots of time and there is a ton of information on them. The gen 5 I am working on for my Camaro project and it is not as much to be found yet.
Dave

 

edmc4044, If you have the choice of the 6 speed as opposed to the original 4 speed my choice would be the 6 speed 10 out of 10 times. I recently completed an L83 and 6L80 in my '63 Pontiac. Having the 4 speed in my '93 GMC there is a world of difference in the driveability between the two transmissions.

As for wiring, I putzed around trying to make the factory wiring loom work before taking the engine out of the wreck and finally gave up. I went to Howell Engine for a stand alone loom at the advice of a friend of a friend who does this stuff frequently. The loom fit perfectly and they reprogrammed the ECM on the bench. They got amazingly close on the program, been driving it for a couple of months now and if I can find someone reliable to put it on the rollers there are a couple of gremlins that probably would be fixed with a final tune but it is not at all critical.

My vote on the wiring would be to bite the bullet and get one from an aftermarket supplier. Just exercise caution who you order from as Howell was not my first contact. The first loom got sent back and fortunately my credit card company got me my money back. If you order a loom you might want to check that the section that connects to the ECM is long enough to remotely mount the ECM under the dash. On the Pontiac I mounted the ECM under the dash and the engine part of the loom penetrates the firewall right behind the RH valve cover and goes directly to the engine. Makes a very clean installation where the wiring is concerned.

The only other problem that I encountered is the charge indicator. I have not yet figured out how to operate an idiot light off of the alternator that came with the engine. (2015 Silverado). I have been told that someone makes an electronic box that can be easily wired in to trigger an idiot light at 11 volts but I have not taken the time to look into it. Been having too much fun driving the Indian to take the time.

At the time of the installation I installed a Comp Cam and put in a DOD delete kit. Don't know how the engine ran on the original cam but I could not be more pleased with the Comp cam. If you would like I will dig through my impeccably clean garage (yea right) to hopefully find the cam card and give you the specs as it was a custom grind

Good luck on the project

 

THANKS exactly what i was loooking for.

 

Some other things I forgot about are fuel delivery. There are extensive articles out there that state you need the factory fuel regulator to properly feed the direct injection engine. If this is just a daily driver I can state categorically that using the early 2000's Corvette filter/ regulator with a frame mounted pump will give you a solid 50 +- psi at the engine fuel connection. You will need a 3/8 return line into the tank, I adapted one into the tank sending unit and it works fine. Being a pickup it is entirely possible that there is a tank out of a newer truck that has an internal pump that will fit. That would have the advantage of internal baffling which prevents the fuel from sloshing away from the pickup. That option does not exist on my Pontiac and I did not want the expense of a custom made tank so I just fill the tank more often. I have noticed that when I get down to about 4 gallons in the tank that the pump starts making noise, probably picking up a little air.

Another thing is that the 6L80 has no provision for a mechanical speedometer. Any wiring loom you get that is PROPERLY made, not all are, will have a speedometer wire. I used an electronic to mechanical adapter from Dakota digital to make the speedometer work. Mounts under the dash connects with a couple of wires and is easily programmable.

Finally if your truck has A/C you can use the Gen 5 compressor. It is a variable displacement which will not work unmodified on your truck. I do not remember how they control the temperature on the 68's, if it is controlled with a low pressure cut off switch in the return line from the evaporator you can use the same system on the gen 5 you just need to also power up the variable displacement with the clutch wire. There is a connection on the rear of the compressor one wire needs to be grounded the other needs to power up when the clutch is energized. That is working fine on my installation.

Hope that this all helps so you do not have to figure it out on the fly.

 

Dave,

Don't know how far you are along on your gen 5 project but I have answered all the problems with a gen 5 installation. Power steering pump, vacuum source for the power brakes, connecting up the crankcase fresh air to the valve covers redirecting the lower hose outlet on the truck pump if you are using that. and a host other issues that came up on my 6 month install as I was figuring all of them out. If you are dialed in great, if not ask me as I probably was there.
Dwight

 

Hello GENIIIDude
May I ask if you got any other wiring diagrams for the L83 engine? I got an L83 from a 2018 Suburban that is to be put into a 1988 Silverado.
The harness that came with the engine is cut where it was connected to the under-hood fuse/relay box (I believe it is)
I also got many other things to solve. For example the fuel supply, I am planning to try using the Silverado in-tank fuel pump, with a fuel pressure regulator at the engine, connected to the fuel return line. Perhaps this will not work?
There is a grey connector, similar to the ones that connects to the ECU, that also have been connected to the under-hood fuse/relay box (I believe). It is hard to know where all the wires belong, without a wiring diagram showing it.

Any help are appreciated
Regards Tomas, from Sweden

 

I am trying to swap an l83 into a friends jeep. He has an e92 ecm and an t87a tcm. Will these work together? We had a t87 but for some reason the hptuners showed that the tcm was not being recognized. This is a new harness( I won't say from which place on thread) that has had several pins loose and no help from company on any of it. Can anyone help trace the pin out?

 

Guys,

I am not capable of diagnosing anything on this kind of swap. The last car I built had an AFB carb and points in the distributor. I can tell you what I did. On the advice of an acquaintance that has done several LS swaps I purchased a wrecked 15 silverado so everything came off of the same vehicle and I had all the widgets that I would need for the swap. The engine is an L83 and the trans is a 6L80E For the wiring I used Howell Engine wiring only because this acquaintance had successfully used their wiring on several swaps. Howell took all the information regarding the usage, cam, final drive ratio and a lot of other things pertinent to the swap and fabricated the loom and did a bench program on the ECM. The wiring comes with an adequate installation manual for the installation. Initially I had problems with bad sensors for whatever reason but once that was straightened out it runs fine.

The problems I encountered installing it into a 63 Pontiac Catalina were:

Power steering pump. Because of hood clearance I was not able to use any aftermarket systems I looked at so I fabricated brackets to tuck the pump into the area formerly occupied by the vacuum pump. By adding an idler pulley and moving the tensioner to a different location I was able to use a pump off of an 06 truck I can supply details of this if you need.

Fuel supply. I used a Walbro frame mounted pump and the 2000 to 2004? Corvette filter regulator. When properly plumbed it regulates the fuel pressure to the engine at an acceptable psi. Don't remember what psi but it does work. If you use the Walbro pump make absolutely sure that someone does not substitute one of the Chinese knock offs. I was not aware of this and my original pump after about 5 or 6000 miles started overheating and I had to be towed home twice before I figured out the problem. Walbro also makes an in tank version of the pump that should be easily adaptable to the original in tank system.

Oil pan. for both engine and trans. Engine I used a Holley pan because it was the only one I could find for the LT engine. I deleted the engine cooler lines because for my application they made no sense. Transmission, ground clearance was a problem so replaced the truck pan with a pan and filter off of a G8 pontiac.

A/C. I used the original compressor but had to modify the variable displacement. To regulate temperature I used an adjustable low pressure switch to trigger the clutch but also had to power up the variable displacement valve. Power off and the variable goes to the minimum displacement. You need to power up the valve on the rear of the compressor to get the maximum displacement I just powered it up with the clutch power wire.

Radiator. I used the truck radiator, A/C condenser and cooling fan combination. The factory truck cooling fans will not work because the original system was extremely complex to regulate fan speed and you can not just power up the fans because they will not work. I adapted fans off of a late 90's vintage Caprice only because I happened to have them in my garage.

I did use a Comp cam and deleted the DOD on the engine. Apparently you can not just replace the lifters to delete the DOD because the cam profile is different on the lobes for the collapsible lifters and you will wind up with low compression on those 4 cylinders. Again I relied on information from people that are familiar with the LT engine and went with Comp. They did a custom grind that performs in exactly the RPM range I wanted.

Intake air. My original thought was to use the factory filter box and intake. Available space in the under hood area eliminated that thought. I wound up using an inexpensive aftermarket tube and filter for an ls engine. The problem was that the tube is 4 inches and the original was 31/2 inches. I cut the original filter box apart and adapted the MAF to the tube. I also took the original diffuser out of the filter box carefully sized the OD to give a tight fit into the new supply tube and positioned it exactly as it was in the original filter box to get the air flow correct across the MAF.

O2 sensors. When Howell programmed the ECM they eliminated the rear O2 sensors. I used the first foot or so off of the original truck exhaust and adapted it to the Pontiac head pipes which positioned the O2 sensors in the factory location.

If I have forgotten anything, get back to me and I will try to help.

 

I don't see which pins need to be deleted.

 

Hello, thanks for the information
I am swapping an L83 from a 2018 Suburban into a K1500, 1988.
I would be glad if you could help with this:
1. which pin on the ECU can be used in order to pull the fuelpump relay?
2. I got a twin-fan setup from a Chevy transsport. One of the fans got two speeds.
Which pin can I use from the ECU to start both fans at full speed when needed (through relays)?
/tomas

 

So where do the 2500 an 2501 gmlan wires go? from ecu to tcm an are they spliced to data port?