6.2 to 6.5 swap

[Thermal Jock]

Hi Dr. Lee et al,
Found a good deal on a 97 6.5 motor w/90k miles. Truck cared for well right until he rolled it. Still runs strong!
Have an 87 Burb w/ a 6.2 that's getting tired. Want to swap the engines, but worried about the electronic inj pump, vacuam for the tranny and turbo, amd wiring for them and the ECM. I have a TH400 tranny, not sure about the TV adjustment.
Can I trade in the elct. IP for a manual one? This 97 has a turbo, but do to confinement I'll prolly leave the Banks on. I assume it's all been done, I searched and got great info, but I'd like to know especially if I've got to get a manual pump. Thanks for all the great posts!

[CleviteKid]

This swap is very doable if you put a mechanical pump on the '97 engine. Before you jump in, do more research in the Members Area of www.TheDieselPage.com (http://www.TheDieselPage.com) about swapping. Also, study the R&R book - it is a good introduction to the various systems, as is the on-line Trouble shooting section of TheDieselPage.

Someone else will have to tell you about the TH400, my experience is limited to the 700R4. We will both learn if the TH400 has a TV or a vacuum modulator.

Dr. Lee :cool:

[britannic]

The mid 80's TH400 installed in our trucks use a vacuum modulator and the TH700R4 uses a TV cable.

[Thermal Jock]

Thanks for the correction.
I did the deal. Wouldn't have without the Diesel Page to get somewhat lined out. It'll be a learning experience, but it's getting cold here, and gives me and excuse to drink beer in the shop anyway.
Posting to the 6.2 forum also, great stuff!
Willprolly get a mechanical pump (4911?) to mount up.
Doesn'e the water pump have to get switched out? Does the 6.2 WP provide enough flow for the 6.5?
I'm missing something here-- can I leave the serpentine belt system in it?
Thanks!!

[britannic]

The later 6.5L water pump runs couinter clockwise with the serpentine set up, I seem to remember there were a few early 6.5Ls with standard drive belts and clockwise rotation water pump.

The later pump and redesigned water crossover are superior to the 6.2L setup, so IMHO, go with that, rather than retrofitting the old gear.

[dunsbr]

Hi Dr Lee,

Ive been lurking and reading previous posts for the last couple of months to get a better understanding of the 6.2 before I posted, but this post has prompted me to stop lurking.

I have a 1987 Humvee with a 6.2 and 3 speed trans.
The engine is in surprisingly good condition for a "surplus" vehicle. However, the poor old girl could do with a bit more "grunt" and a 4 speed trans. ;)

I have just been offered a 20,000 mile 6.5 TD long motor from a wreck and a military 6.5 IP for a "very competive price" and am thinking I should rebuild this engine as a project to install along with the 4l80e and 242 T/case I have now sitting in my garage.

My aim would be to convert the engine to NA (for reliability) and to get over 250 hp while retaining torque for my 4 wheeling activities.

Based on my reading through the list, I see that my list of activities should be:

Stip down the engine,Hot tank the block,
Line bore and square the deck on the block,
puchase new NA pistons, Shot peen and polish the rods, Balance rotating assembly, "cc" each cylinder, port and polish the heads to match Hummer inlet and exhaust manifold shapes, install new Cam shaft, fit geared IP drive, fit stud girdle kit, fit V Belt high flow water pump, Rebuild using GM gasket kit with Felpro Head gaskets and TTY bolts. Rebuild the military IP(24V and hardened internals), have injectors rebuilt.

Have I forgotten anything?

Based on the above, I have some questions for the list.
1.What compression ratio is optimum to boost HP but retain good 4 wheeling torque?
2. Is Ceramic coating of pistons worth while on a NA engine? (also as I will be "cc"ing each cylinder I may need to machine the piston crown slightly on some pistons to ensure an equal volume. This will remove the coating on some pistons)
3. What is the best cam grind for my application? (Standard or the crane grind I have read about)
4. Does the 6.5 have a geared drive for the IP as standard equipment? (unlike 6.2 chain drive)
5. What spec should I have the Military IP built too?
6. What spec should I have the injectors built too?

Sorry to be so long winded, but I have come from the world of Gas engines so Diesels are a black art to me! But I am learning smile.gif

Cheers

Brad Dunstan

[NH2112]

You'll never even come close to 250HP with an NA 6.5L. Keep the turbo, at stock HP levels it won't be any less reliable than an NA and even at 250HP you won't have any reliability problems. I'm assuming you mean 250HP and the flywheel and not the rear wheels - that's a lot to ask for from a 6.5L!

[CleviteKid]

Phil is correct; with an NA 6.5L you will be compromising reliability just to get to 200 HP at the flywheel.

Remember my advice: "From a thermodynamic perspective, EVERY diesel engine should be turbocharged."

Dr. Lee :cool:

[dunsbr]

Thanks for the feedback.
I'm pretty commited to not running a turbo though.
The list of mods required to the Humvee to take the turbo, whilst do-able, is extensive.
Also as I'm located in Australia, getting those Humvee parts can be problematic too.

Regarding reliability, it seems that the rear mount turbo's on Hummers combined with low air circulation at the rear of the engine bay "may" cause excessive heat build up leading to block craking around #8 cyl. The NA Hummer's don't seem to suffer from this. Given the rarity of 6.5 parts in Australia I'd rather not risk a cracked block.

So, from my list of proposed activities what is a reasonable output to expect from a NA 6.5?
I guess what I'm after is a Humvee that goes a little faster than 60mph and will still off road sweetly. I'm also hoping that the attention to detail inside the engine will make it a little smoother and sweeter running too.

There's not a big community of GM diesel builders over here, so any comments, or lessons learnt to help in my rebuild will be truely appreciated

Thanks in advance

Brad Dunstan

[NH2112]

From 12 years of experience with NA humvees in the army, I can tell you that the lack of a turbo does NOT negatively affect them for off-roading.

[dunsbr]

Hi Phil,

I agree with you.
Off road my M1026 is way faster than my friends Land Cruisers and Nissan Patrols.
Its the road trip to the 4x4 sites that's painful! :rolleyes:
All my buddies wave at me and smile as they pass me on the way out of town.

Hence my desire to fit the 4 speed and install an upgraded 6.5. The great off road performance of the truck is why I'm mindful of not adversly affecting Torque in my pursuit of some extra horses.

Cheers

Brad