6.2 build turns into a 6.5 block!

[K5-CJ5]

I just got, what I was told, is a 6.2 from an 82 3/4 truck. I pulled the motor, truck not registrable, and found that it is a 12555506 casting from may of 1997. I got the entire wrecked truck for $50 and am planning to sell the th400 and np208 tcase, and put the motor in a rock crawler in front of a sm465, np205 set-up. I was told 69,000 miles but seeing as its not even a 6.2, I'm not gonna trust that. I have decided to rebuild the motor and see what I find. Is there any mods I can do to make sure this block doesn't crack like I have heard the 506 castings tend to do. Any performance mod advice is always great also. This engine will not be towing at all, but used as a rock crawler, sometimes mud only. I am also looking for a turbo for my build if anyone has one they want to sell.

[a5150nut]

You might check Robins theads on Lock Stich.

[Robyn]

Sounds like a fairly good score.

Once you get inside the little beast you can see if it has any cracks in the block anywhere down in the center main webs.

Depending on the miles it has on it, you may have a very good foundation to build on.

We have a pretty good "Build tips" thread that can help a bunch.

Good luck and keep us posted

Robyn/AKA Missy

[Kennedy]

I just got, what I was told, is a 6.2 from an 82 3/4 truck. I pulled the motor, truck not registrable, and found that it is a 12555506 casting from may of 1997. I got the entire wrecked truck for $50 and am planning to sell the th400 and np208 tcase, and put the motor in a rock crawler in front of a sm465, np205 set-up. I was told 69,000 miles but seeing as its not even a 6.2, I'm not gonna trust that. I have decided to rebuild the motor and see what I find. Is there any mods I can do to make sure this block doesn't crack like I have heard the 506 castings tend to do. Any performance mod advice is always great also. This engine will not be towing at all, but used as a rock crawler, sometimes mud only. I am also looking for a turbo for my build if anyone has one they want to sell.


First I'll say that ALL 6.2 and 6.5 blocks crack. The turbocharged ones had more of a tendency to fly apart due to the increased power levels. Second I will say that there is only one way that I have seen to eliminate the cracking. Splayed main caps.

[K5-CJ5]

Thanks for the reply, Ill check out the build threads. I haven't ever had a 6.5n/a and am having trouble finding a turbo for the motor. How big of a difference will I see without the turbo in off-road conditions?

[DmaxMaverick]

Thanks for the reply, Ill check out the build threads. I haven't ever had a 6.5n/a and am having trouble finding a turbo for the motor. How big of a difference will I see without the turbo in off-road conditions?


Probably none. For crawling, mud and slow-going, N/A is better, IMO. The off-idle power is better, smoother, and more consistent than with a turbo. Under the boost envelop (which is essentially operating N/A), a turbo is a drag on the system. I prefer a non-turbo for this (and have/use one for this). If you haven't already figured it into your plans, get rid of the stock 10-bolt rear end, and upgrade. The 10-bolts are disposable for crawling (4-Lo and slow). My 85 would kill one in short order (and did, repeatedly). I upgraded to a 1978 12-bolt, and it's lived happy since. The SM465/NP205 is a very good choice for your purpose-built rig.

[K5-CJ5]

Yeah I know about my 6.2 t/d and the 10 bolt rear end! This new rig I have a 14BFF, and a dana 44 front. Both have ORD upgraded shafts. Im not new to building rock crawlers, just new to the 6.2/6.5 diesels. I'm tired of messing around with computers getting wet in river crossings, and distributors. I have also done a 6.0 swap but have been happy with wheeling my 1982 6.2 T/D blazer which isn't intended to be a crawler, but it does great over rocks and even better in the snow. The SM465 NP205 combo with 4.11 gears and 38" tires should be just about right behind the diesel.

Since everyone is so knowledgeable hear, I want to run the exhaust through the hood, was going to come off turbo with a 90 but if I can find the turbo will modify. Is there any power loss by doing this?

[DmaxMaverick]

It sounds like you have this well in hand. The only electrical required will be for the IP, which is straight 12V to two connectors (ESS and HPCA). Even those can be made to operate mechanical (which would be ideal for an off-road only rig).

Another suggestion:

Electric fans, or HMMWV hydraulic fan clutch (PS pump supply will work fine for this). This will eliminate the fan during deep water crossing. Viscous fan clutches (OEM type) or direct-drive fans are disastrous in deep water. During slow, low RPM engagements, the viscous fan clutch is essentially useless, anyway. A hydraulic clutch would allow manual or electrical engagement (automatic, manual, or both). The fans are designed to move air. When we try to get them to move water, bad things happen.

[K5-CJ5]

Thats a great piece of advice. I wanted to go electric fans but to pull enough CFM can be hard. Ill look into the hydraulic fans I haven't ever seen one, or new they existed. My P/S pump will be running hydro boost and box, still ok for the hydraulic fan?

[DmaxMaverick]

The hydraulic fan clutch is low volume (negligible amount, not dynamic). It is only an on/off clutch, and does not require hydraulic flow to rotate the fan. Simply put, hydraulic pressure is used to engage a clutch, much like electrical is used to engage an A/C clutch. It will have NO parasitic effect on the existing system. I have one, slated to go into my Blazer. It's a "standard issue" item on many HMMWV's. I could dig it up and post a picture, if needed. I may be able to find one for you, if you decide to do it.

[K5-CJ5]

If you could post a pic that would be great! What is the cost on the units usually?

[DmaxMaverick]

I gave less than $50 for it, from a TDP member with a bunch of parts. It was the clutch, with the pulley and a (like) new water pump. He may be able to source another. I'll try to contact him, if you want.

Here's a site with a picture of just the clutch: http://www.stock-number.com/06Class9HUMMWVCooling.htm

If you need a pic with the clutch mounted to the pump with pulley, you'll have to give me some time. Some idiot didn't label all those boxes in my barn.