My Experiences in overhauling an 8v71 Detroit in a MC-8 automatic.
When I bought my bus, I knew it had a tired engine and needed some work. There was oil coming from the air box vents. When I first called about a HO kit, I asked whether the blower seals could cause this. The answer was not likely, I was told the oil is probably from the rings, but it was simple to check the blower by opening the top and looking in. If it was greasy, then they were leaking.
I put each wheel on two 3” blocks, and blocked between the Air beams and frame, and let the air out of the airbags.

I set out to build a jig to remove the engine.  It took a while but I designed one that would not only remove the engine but also act as a safe engine stand for the heavy unit.  I carefully made a template of the unused bolt holes in the bell housing. I then used the template to drill holes in Two 2x4x3/8x4 angles, and bolted them to the bell housing.  With 4x4x1/4 SQ tubing, I laid two pieces 4’ long and 40” apart on the floor. I crossed these two with two more. One cross would hold the front motor support by means of two upright pieces of the same, with receiving notches. The other would connect with tubing uprights to the bolted angles. I welded the crosses, the up rights and the angles together. I attached the crosses to the length pieces with angle clips and bolts. I cut holes in the bottom of the length pieces to place and weld the nuts. This makes it possible to get it all in place without raising the bus any more. I just inserted a pallet jack and rolled the whole thing out.  It worked like a charm.

I proceeded to remove all the gear-mounted accessories: alt, comp, and PS. Now it was time to build the lifting jig for the trans. I built a rectangular frame of 1x2 SQ tubing, that would go around the pan, and allow the pan bolts to rest on it, and run some angle down to rest on cross pieces. I could slide it under the trans, raise it into place, and slide a pallet jack under it. I had removed and installed several 640 Allisons from trash trucks. The conditions were always less than ideal, using a floor jack and the balancing act, once on a snow covered drive. This removal was almost mystical it was so easy. But first I had to remove a plug on the bell-housing to get at the flex plate to flywheel bolts. These bolts can cause some concern, as it would be easy to drop one down into the bell housing.
After the trans and flex plate removal, I had to figure how to support the bell housing. It has hocks on the top for this purpose, but my engine stand mounted to the bolts in the bottom of the bell housing. I supported the rear of the engine with two hydraulic jacks, and removed the four bolts holding the rear cross to the length pieces. I lifted the cross with the pallet jack and balanced it as I rolled it out.

 The seal turned out to have a sleeve, and upon removal I found enough grove in the crank that I decide to go back and get the one with the sleeve. I had decided to replace the Idler Bearings as well. I called around to find the bearings, as I knew they would be cheaper at Allied Bearing than Detroit. They did not have the bearings, but could get them and the price would be $35 each.   Another trip to Detroit anyway, so I asked about the bearings and was pleasantly surprised to learn the pair was just $100, and included the spacers that go with it. I got the bearings installed and the idler set to advanced, then I start to install the seals. It was a directional seal, and I was not sure it was right. All rights and lefts on a Detroit are from the flywheel end (heads, banks etc.), except the direction of rotation. It is measured standing in front of the engine, RH being clockwise and LH being counter clockwise. The seal was definitely wrong. I called the parts man and he was sorry, but he had given me the part called for with my serial no. I decided to check the bell-housing gasket and it was wrong also. No hump for the blower gear. Turned out to be for an inline 71. When I arrived, he had the proper seal laid out, and there was a gasket laying on the counter that I needed. I was impressed that he had realized the mistake, only to learn it was ordered for some one else. They had to rob an OH kit to get the gasket, but were willing to, just to get rid of me.
After thoroughly cleaning the surfaces, I installed the bell housing. I used two long bolts to guide it into place. The pallet jack worked very well in the installation, allowing me to turn the crank and ease the seal over the crankshaft. I torqued all the bolts to spec and installed the flexplate.
I then started with rest of the job by cleaning the top of the block and the sleeve holes thoroughly. Next was the main bearing installation. They rolled in very easily. Some of the main caps had some build up that required cleaning with emery cloth, but all in all it was pretty easy. Now I was on to the jugs and pistons. I removed the two bolts holding the rods onto the pistons, put the two-part pistons together with a seal in between, and bolted the new pistons to the old rods using locktite. I put the rings on by hand, taking great care to get them on in the right direction, and with proper spacing between ring ends. I used a ring compressor to load the first one into the bottom of the sleeve with no problem. The next one seemed to hang as it went in. I pulled it back out and found I had chipped the corner of an oil ring.  I examined the sleeve and the chamfer at the bottom. I could see how easy it was for the ring to get caught. I called my machinist, who told me the ring compressor is the method he uses. I know others that use it also, but I just did not trust it after breaking a ring. I tried to locate a loading sleeve to borrow, with no luck, so I bought one, and another set of rings at Detroit for about $200. You could probably get a set cheaper from Snap On or the like, but I didn't want to spend the time looking. It is much quicker with the loader but, more importantly, it is safer. Installing the sleeves into block was much easier than I had expected. I bolted a large washer on a head-bolt hole to hold the sleeves in place so they didn't come out as I turned the engine over to the next hole. I torqued rod and mains to spec. The bolt flange of the oil pan was really warped from over tightening. I carefully straightened and aligned the flange with a hammer and anvil. I was careful to clean the gasket area and use a good sealer with the new gasket. I tightened the bolts to specs in 5# increments.

I installed the new injectors into the rebuilt heads, supported by blocks to make sure the tips did not get damaged. I Torqued the rocker rack and installed the fuel tubes. I balanced the valve bridges by making certain there was equal pressure on the stem of each valve and that they were not binding on the bridge guide. I would back the adjustment screw out clear, hold the bridge down and screw the screw to first contact, mark, screw to snug (binding on bridge), and mark, then return to the half way point and tighten the nut.

The head is too heavy to set in place by hand, so I built another jig to lift and balance the head, as described in the Detroit manual. I used a cherry picker and two alignment studs to place the heads. I let it down to within 1/2 inch of the block, and started all the head bolts. I carefully let it down and tightened the bolts to contact. I torqued the bolts to spec, using the proper bolt sequence at 50# increments.
 I set the valve clearance by turning the crank until the injector was depressed and adjusting to .016. This was a lot more difficult than I thought. When you tighten the nut it changes, so it took some time for me to get it right. The 16 gage should have some pressure, but the 15 should slide in with no pressure.
The Injectors set on the down stroke of the valves, with a special winged tool. Mine was a 1.484. Again it took some time to get it right. The Tool should just swing over the retainer top of the injector. I found a drop of used oil placed on the top would help.  I went back over the settings of both of the valves and the injectors three times. It is important to be right. I installed the fuel rack, and the fuel rods.

Now come the part that gave me the most concern. 1. I set the governor gap by wedging the governor out with a tire tool. If it is between .003 and .016, it is OK, If not, reset to .008. I set it and rechecked it, making sure the governor weights were fully extended.
2. Adjust the fuel rack. (Note: This is where I made a mistake by not backing the idle screw out ½ inch, so the low speed idle spring would be compressed.) The idea is to have all the injectors at full fuel at the same time the governor is at full fuel, and no tension or slack on the fuel rods or fuel levers. It is not complicated, but very important to have all these mechanical parts in sequence.
 I disconnected the clevis pins on the fuel racks, and tied the governor into full fuel with a bungie cord. I backed the adjustment off on the all fuel levers until I could easily slide the clevis pins in both racks with the racks in full fuel. I was now ready to do the most crucial adjustment. With the opposite rack disconnected, I slid the pin in the clevis rack I was starting. I made sure there was slack in all the rack levers. I started with the first screw nearest the clevis.  I turned the screw until it had the injector in full fuel (bottomed out) then backed it out a little. I took the end of my screwdriver and pushed on the bottom of the injector U, rotating it to the right. I then turned the screw in until the U began to rotate to the left and all the slack had been taken out or the clevis pin connection. I tapped on the bottom of the U (rotating the injector arm right) to see if it bounced back to the left. It didn't, so I turned the screw and watched the U rotate to the left again until it just stooped. I locked the nut and checked the bounce on the U again. This time when I tapped down (rotating to the right) it returned to the left.
Then I checked the clevis pen connection and the arm could not be rotated open any further. Holding the rack open, I removed the pin to see if it would easily slide into the connection with no slack, and it did.   I continued down the rack with the procedure, checking not only the injector I was adjusting, but also all the previous ones. When I was finished with the fourth one I pushed on each lever to be sure there was no slack in any of the rack levers to injector U connections. I held the rack to open, and pulled and replaced the Clevis pin again to be sure I had not added tension to it. It was fine. I disconnected the clevis on this rack, pinned the one in the other rack and started the procedure on it.
When I had finished, I attached the clevis pins to both racks. Holding the rack in full fuel, each clevis pin could be removed and replaced with ease and there was no slack in the connection or in any of the levers connecting to the U on the injectors. I then released the throttle and it returned to the start position on the injectors. I pushed the kill arm, and watched the rack pull all the injectors to no fuel and then the rack moved a little more, putting spring tension against the injectors, holding them in the no fuel position. I released the kill arm and watched as the rack returned to the start position. I worked the throttle several times to be sure there was no binding in the fuel rod, put on the valve covers and that’s it.
I began to reinstall the transmission and all the rear accessories, a good day’s job of cleaning gaskets, sealing and torqueing. I was very careful to clean each gasket surface and use a good permitex sealer. I wanted to have a “no leak” Detroit.

It would be foolish to not check or change the thermostats.  I ordered two from the local auto parts store. 2@ $30. Probably cheaper at Detroit, if I had remembered to ask. I took the old one out to compare when I picked up the new ones. The old ones were heavy brass. The new ones were very cheap looking in comparison. I decided to check the old ones and reuse them if they were good. I also put the new ones in the oven at the same time. All opened at the same time, about 180, except one old one. I examined it and found the mounting base screw to be stripped at the stem. When the opening occurred, it just let the stem drop further down. I really don’t see how any water was getting past, anyway, I was very glad I checked them. From the looks of the old Detroit thermostat, I don’t think they diminish in opening temperatures, as easily as auto models do. I will save the old Detroit thermostat for a spare.

I started cleaning inside the engine compartment today. It is hard to believe the amount of grease and grime build up. I did find that diesel cuts it really well. Since I have the bus inside on blocks, I will try to clean it by hand.
I am going to have to remove the rear end center section and reseal. I also have a wheel seal leaking that I will fix while I have the axle out.

I removed the 3rd member by positing it on a floor jack. It appears to have been rebuilt not long ago, just as the seller had told me. It was changed to a 3.33 ratio also.  I cleaned and resealed it with black silicone.  The weight made it a trick to balance and reinstall.
The wheel seal didn't take long either.  I was wishing for a wheel remover when I realized I already had one, a pallet jack. It worked great to slide the wheels off and reinstall them with great ease.

I tried to find all the air leaks while the engine was out. Most were valves or regulators, and easy to repair with an assortment of O rings.

I got the engine reinstalled today. Primed the fuel with a small hand pump until it came out of the return. I filled the oil filter and turned the engine over with the governor in no fuel, until the oil pressure came up. I then placed the governor in idle position and cranked again. It didn't start, so I increased the throttle just a little and it fired. I let it run about 5 sec and shut down. Now to get the radiator hooked up.
I replaced every hose on the engine, and filled the radiator with antifreeze and distilled water. I started it up again and let it run to warm. It is perfectly smooth, the time I took to set the injectors, valves, and rake were well spent. I set the idle at 550 and the fast Idle at 1,000.  The temp came up to the point of circulation. Sounds good.  The gages and the starter button in the bus don’t work.  I have a new oil pressure gage in back. With the 30-weight oil, it started with 50lbs and when it warmed it had 10lbs. I will change to
40 weight in about two-hundred miles. I thought the 30 would flow faster for first start lubrication.
I hooked up the transmission linkage, and adjusted it. I had the drive line completely out for the third member gasket seal. I installed it with new bolts.  The driveline was heavy to lift into place while lying in such a close place.
I checked the electrical plugs and found one loose. Now the instruments work.  I had some spillage from the air box vents on start up, so I plumbed them into a container on each side. With the air up, I removed the blocks from the frame/airbeams. This thing has been sitting in my shop for several months, so I am anxious to see it rolls again. I eased it forward, carefully rolling off of the two, 3” timbers under each wheel. I drove it around the block. When I first accelerated, it puffed some smoke, but none since. It didn't have much speed, barely having enough to shift the Automatic.  I was pretty sure the governor speed was low, but I didn't want to run it full out to set it, until it had run some. We checked everything, and took it on another drive, this time 20 miles. I brought it back and installed the breather and connection pipe. I had gotten the snorkel bolted on the blower at a “right angle” but that was wrong, so I had a tough time figuring out how to connect the pipe. It is a little tougher twisting bolts with the engine in place. There is not much room and everything becomes more difficult. I know you can run the rack with the engine in the bus, but it is much easier out. I had forgot to bolt the accelerator linkage to the back of the engine. A two-minute job took me 45 minutes. I always think I can remember where everything goes, but I can’t. It is a good idea to take pictures and make notes.
I will set the governor speed tomorrow, that should give it full power and speed. My wife commented how quit the engine was. I fixed several exhaust leaks in the piping and gaskets. And So far… No oil leaks!
After increasing the high governor speed it still didn't have enough power. I retraced my steps and decided it had to be the fuel rack. I had not backed the Idle screw out before setting the fuel rack. At the time I could not see it would make a difference. I pulled one valve cover, and backed the screw out the recommended 1/2”. At full throttle the injectors were not at full fuel.  I reset the fuel rack. It was not as hard as I had thought it would be, but it is still a lot easier while out of the bus. I replace the valve covers and breather pipe. On start up, I adjusted the idle screw to 550rpm with a mechanical hand held tac on the crank.  I now had a lot more power and still little or no smoke.
My alternator was not working, but I could jump it and make it work. It took me a while to realize I had the wires switched on the alternator. When I took them off, I made a note of the black wire and the yellow wire. When the wires were cleaned, they were both yellows (terminals).
The water pump had a noise at idle. I drained the coolant into a 30 gal. plastic barrel to be able to remove the pump. I wished I had checked it before I put the hoses on. It is not much trouble to remove, just dealing with the hoses. The pump is sealed to the block with a flat “O ring”.  A rebuilt one at DD was about $200 exchange. I just used a barrel pump to replace the coolant. I was unable to locate a source for aerosol cans of DD green until after I had it reinstalled. It would have looked better if I could have painted it while I had it in the shop.
I installed an alt type tachometer in the bus so I could have a better idea how the engine was performing. It is  running  1771rpm at 65mph, with Firestone Hp3000, and a 3.33 Ratio.

All and all I think the OH was a great success. I enjoyed the learning experience, and I didn't make any fatal mistakes. On the positive side, I not only have a good engine, but I know what is in it. On the negative, if I have an oil leak, I only have myself to blame.
  New added 11/12/99
My 8v71 had a leak in the front main seal after I overhauled it. I had hoped the front seal would be OK.  I picked up a seal at DD the last time I was in Tulsa, so I could do the job the first slack day.  Today was that day. I had a pretty hard time getting the hub off with a puller. It was really tight. There is a heavy sleeve on the crank that the seal runs against. It came off by hand. The sleeve had a deep crease in it where the seal ran. It appeared to be the same on both ends, so I just cleaned up the other end and reversed it.  If I had known about the sleeve I would probably have bought a new one, but I don’t see why this is not just as good.
The Hub had a lot of damage to it and many gouges. I also notice there was no half moon keys in the keyways. I went into town (5miles) to my local parts store and found two key that were just right. I had to clean the notches with a file to get them to fit proper.
I then cleaned up the inside of the Hub and the Crank that both had gouges, with emery cloth . I pulled the old seal out and replace it with the new. I put silicone on the inside of the sleeve, and slide it over the crank and through the seal. The Hub went right on, and slide up against the sleeve.  I tightened the center nut down to torque spec. I then put the pulley back on and tightened it up. The belts back on and it is ready to go. Not nearly as much trouble as I was afraid it would be.
 
 Mallie Lennon / Eufaula, OK
MC-8

 
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