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assembly Our trusty 6.2L C motor had done us well, and was as reliable as ever at 300,931 miles. It was just very tired, and needed a replacement or a rebuild. Besides, we can always use more power. To minimize downtime -and we weren't in too big a hurry-, we chose to build a whole new motor. We located an old military 6.2L that was used in a CUCV not too far away, so we hooked up a trailer and hit the road. The engine was located in a US Army crate specifically made to carry engines, and in this case it housed our new-to-us 6.2L. We got a military motor, an extra head, another DB-2 pump, a hummer intake, and the cool green crate. We set to taking apart our new 6.2L, and were stunned when we found that there was nearly no wear on parts like lifters and pushrods. Once things were taken apart and individually labeled as to their exact location and orientation, we took the block and heads down to the machine shop to get magnafluxed. We chose Trinity Castings in Dallas, TX to do all our machine work. They have a solid reputation for quality, and routinely perform machine work for large diesels, so our motor was no big deal. Once we got word that our block and heads were good, we had the heads rebuilt with new seats and valve stem bushings, the block was line bored, and the cylinders done 0.030 over. Our crank was polished; NOT ground. The GM manual specifies that the 6.2L crankshaft has a nitride coating and is not to be ground. While our stuff was at the machine shop, we wasted no time in starting our pile of new parts. We wante to upgrade the cooling system, but the only option for something over the 87gpm pump would be a serpentine conversion and a reverse rotation GM pump at 130gpm. That tacks on another $1000 or so to an already expensive rebuild. That is until Peninsular Diesel in Michigan started offering their 110gpm standard rotation water pump.
Here is the new crossover pipe, a standard output and the modified one, the throttle bracket, and upper hose. Not pictured is the 110gpm pump. I paid a call to M&D Distributors in Dallas, and got a set of new Mahle 21.3:1 pistons. We took those, our crank, and our rods down to Arlington Automotive Machine to get the race engine treatment. Our pistons were balanced within one gram of each other, the rods were bluprinted and balanced within two grams, and crank was balanced and blueprinted.
Finally we got our block back from the machine shop and were eager to put our balanced crankshaft in its home. But before jumping the gun, any time there has been machine work done, it is highly recommended that you wash the block thoroughly with soap and water, and blow dry with compressed air to prevent corrosion. We installed our crankshaft with new GM bearings. They are actually Clevite 77 bearings, but we needed some undersized units for the mains, so we paid the premium at the GM house for the exact bearings we needed.
After installing the cam shaft with plenty of Lith-Ease assembly lube, we made our way to the front of the motor and installed our new timing gear drive from Diesel Services Group.
The top timing gear is a little obscured by the lower injection gear in the picture. After indexing the injection gears according to their marks, we were able to get the front cover on and torqued. We then installed our newly rebuild DB2 pump. The pump that we got with the engine was a military version, and contained hardened internal components so that it could flow multiple fuels, but went ahead and had it rebuilt to the 4878 specs @ 59 cu mm/ stroke. We installed our dual thermostat crossover pipe at the same time along with the throttle bracket. At the time of assembly, GM had come out with new 12 point nuts to hold the injector pump to the front cover. Since we had plans to adjust the timing in the future, we bought some convenience with these new nuts.
The modified throttle bracket from Peninsular Diesel works well, but has no provision for cruise control. In the future we plan to design and fabricate a new bracket that allows for an after-market cruise control. We installed the pistons at the same time taking note of ring orientation prescribed by the GM manual, and also being careful not to score the cylinder wall during installation. Finally, we had a short block.
We finished out the lower end by adding a brand new 6.5L oil pump from GM, new freeze plugs, a new block heater, and double checking all the bolts to make sure they were torqued right. Now that our heads were back from the machine shop, we could turn our attention to the top end. We had a full rebuild on the heads, new 6.5 "T" sized prechambers, and they were milled.
Before we put the heads on, we wanted to make sure that our new Felpro torque to yield (TTY) head bolts would have perfectly clean interior threads to work with, and ensure that were getting a perfect torque value when it came time to tighten down the heads. We got a bottoming tap at our local hardware store, and used cutting oil to help clean the threads in the block. There is a sealant on the end of the Felpro bolts, but it's a hardened sealant, and we knew that better stuff was out there. We picked up a genuine GM tube of thread sealant with Teflon. It's probably a relabeled brand like Permatex or Loctite, but we wanted to make sure we had the right stuff. We then unpackaged our lifters that had passed an inspection, and were as good as new; we put them back in the exact same hole and orientation. After they were installed and torqued, we picked out our head gaskets and got ready for the heads. After setting on the standard 6.2L Felpro head gaskets, we located the heads on their dowels. Then, closely following the latest torqueing procedure outlined by GM, we cinched down the heads.
After masking off and painting the heads with 500 degree F paint, we fit the pushrods and finished out the valvetrain. With the valve covers on, torqued, and painted, we dug out the injector lines from the parts bin and installed them along with our rebuilt 1800 psi pop-pressure injectors. We installed our dual plane J manifold and oil pan, and finished out details like 60G glowplugs, new motor mounts, installing the cam driven vacuum pump, and adding on the accessory brackets and the accessories. We had put on our PF35 oil filter, poured in our favorite Delo 15w-40, and drove the oil pump to lube the lower end before we put in the vacuum pump. Now we were ready to drop her in.
Up next: adding some boost to our new diesel.
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