M998 6.2 to 6.5l swap questions

[galaxie428]

Hello all,

I have been reading a lot of threads on this swap as many others have done it but I'm not finding anything that answers my question. I would be surprised if this hasn't been answered but I didn't come across it. First, as I mentioned I have a M998 that came with the 6.2. I bought a 6.5 turbo through the gov auctions recently to do the swap. I have pulled the 6.2 and think I have the 6.5 ready to be mounted but have some questions.

I still have the 3l80 though my plan is to swap it for the 4l80E in the future, not sure I have the funds for that just yet. I bought a new engine harness for the 6.5 turbo for pairing with the 4l80 but until I do that swap, is it easier to use the original harness? I ask because as I look at the harness, I am seeing different connectors, specifically for the transmission.

For the exhaust, is there a pipe that would connect the wastegate down pipe to the original exhaust or was it in a different location for models that came with the 6.5 turbo and 4l80 package? I'm sure an exhaust place can make something and maybe that is a cheaper route to go anyway?

It was getting late last night but I noticed that the 6.5 engine harness has a plug with 3 prongs on it but the harness that came over the top of the trans only has two prongs, it looked like maybe it ran over to the STE/ICE-R? What have others done with that?

Thanks for any help/advice you can give.

 

[Mogman]

Allot to process here.
Yes there is a down pipe that will connect the turbo to the M998 exhaust.
You will have to remove the TPS and install the kick down switch on the IP you will also need to install the mechanical throttle linkage for the 3L80
If your M998 had a 60A alternator you will need to add the high current charging leads for the 200A, if you keep the M998 engine harness
I am not sure of any issues you would have running the later harness, most likely just allot of unused connectors that you would want to protect.
You also need to install the floor pieces for expanding the doghouse area which involves cutting out some of the original floor in the doghouse area.
You should to do at least a 1/2" body lift
Many others have done this conversion but I suspect most went with the 4L80, I already had a 6L80 in my M998 when I did the conversion.
Remember the cooling fan turns the opposite direction so you cannot use the 6.2L fan.
Here is the thread on my conversion.

M998 turbo conversion

I am starting to do a GEP turbo conversion on my 1992 M998 I call "Detroit" so maybe some would be interested in the "ride" Back story: When I was getting ready to install the 6L80 in Detroit I knew I was going to have issues with my doghouse, I was using a cable driven tach out of a another...

www.steelsoldiers.com

 

[galaxie428]

I saw somewhere in my research that you do not have to trim the doghouse area with a 2" lift which is what I installed. I hope that is the case though I have marked it just in case. I plan to do a test fit to see, then if I have to cut it, I will.

Yes, I have the 60a alternator. I looked at sourcing all the parts for the 200 amp but by the time I bought all the parts, I was going to have more in the alternator, pulleys, tensioners and so on than I have in the whole vehicle. I plan on sticking with the 60 amp for now and just reusing everything from the 6.2. I did buy a high flow CW water pump and replaced the CCW pump on the 6.5. Not sure if anyone has tried this?

Your conversion write up was great, it was one of the many I read through.

 

[Mogman]

I saw somewhere in my research that you do not have to trim the doghouse area with a 2" lift which is what I installed. I hope that is the case though I have marked it just in case. I plan to do a test fit to see, then if I have to cut it, I will.

Yes, I have the 60a alternator. I looked at sourcing all the parts for the 200 amp but by the time I bought all the parts, I was going to have more in the alternator, pulleys, tensioners and so on than I have in the whole vehicle. I plan on sticking with the 60 amp for now and just reusing everything from the 6.2. I did buy a high flow CW water pump and replaced the CCW pump on the 6.5. Not sure if anyone has tried this?

Your conversion write up was great, it was one of the many I read through.

I see no reason the CW pump would not work, I forgot there are many 6.5L running around with V belts and the CW pump as the A1 trucks that went through RECAP retained the V belts. (personally I would go the extra cost of converting to serpentine belts SOOOOO much better)
You are probably OK with the 2" lift, I think I could have gotten away with no floor mods but access to the turbo pipe would have been a PITA.
I will see if I can find the part number for the down pipe.

 

[Mogman]

I am pretty sure 2990014222826 12460487 Is the down/cross over pipe.
But you are going to wish you got that pipe with the motor, a quick search shows over $900.
If you have a custom one made make sure they build a heat shield on it for where it crosses in front on the trans pan.
I have one source I can check with, you should put a want in the classifieds, I would gladly pay up to 200 instead of letting a hillbilly build one.

 

[galaxie428]

Yeah, I found one for $975, ouch. Good idea though, I will post in the want classifieds.

 

[Mogman]

I would add that doing the floor does not cost very much, there is no reason not to, it gives more access and that is NEVER a bad thing on a HMMWV!!
EDIT the part numbers for the floor kits are 12469253 and 12469252