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Simp's M923 Big Cam Repower

simp5782

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Something to think about, you cannot just bolt a flywheel housing on....Is that what broke or the bell housing on the trans? It needs to be dialed in. If not, the flywheel housing will break at every bolt that holds it to the block. I have a tool if you need it.
I went according to the manual with the guide studs and torque sequence. Flywheel runout is within spec at all.

Flywheel housing broke due to the motor shifting and you can see in the picture the rear ear of the transmission mount is into the bellhousing bracket putting pressure on it. It dug a pretty good mark into that bracket. Power had to go somewhere and that is where and that bellhousing was just the weakest part.
 

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Jeepsinker

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I worked with Fred at AEcom on Ft. Polk in 2016. That guy is an idiot. Won't listen to anyone about anything and he's a terrible technician. I wouldn't let him work on a lawnmower.
 

simp5782

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Sell explanation of what happens when it drops a valve in route to Ft. Polk. In frame time. Should be in on Monday. Going to go down remove the unit and take it to Profos shop since he wont be home and get it all done. Looking at maybe some other tweaks. Engine has standard bearings and liners in it. Gotta replace atleast 2 rods and 1 head and having the injectors reflowed. Believe the injector hung open and caused some mushrooming and then broke the valve. engine had unknown mileage on it
 

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WillWagner

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Explain the injector hanging open causing a "mushrooming" ....PT injectors cannot do that, hang open. they are not pintle type injectors. They will break crimps, that is usually caused by an incorrect tune up. too tight of an adjustment, greater than 6 in lbs...no 1/4 turn past zero lash...that takes up stack up tolerances and the built in travel needs to go somewhere like the crimp or the push tube or a cam follower pin and cam lobe or a split cup. Unused fuel will be routed back into the return except in the case of the split cup, then there will be alot of smoke, but nothing that will cause a valve failure. What is mushrooming? The failure is on 6.... I have seen this before after a repair.
 

simp5782

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Explain the injector hanging open causing a "mushrooming" ....PT injectors cannot do that, hang open. they are not pintle type injectors. They will break crimps, that is usually caused by an incorrect tune up. too tight of an adjustment, greater than 6 in lbs...no 1/4 turn past zero lash...that takes up stack up tolerances and the built in travel needs to go somewhere like the crimp or the push tube or a cam follower pin and cam lobe or a split cup. Unused fuel will be routed back into the return except in the case of the split cup, then there will be alot of smoke, but nothing that will cause a valve failure. What is mushrooming? The failure is on 6.... I have seen this before after a repair.
Ok let's not go with that then and Well it was approx 160hrs after the tune up with around 100hrs of it being work time. Figured something would have happened before then. Every manual I have seen says the injectors tighten to 1/4 screw turn past finger tight for the IBC method.
 

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WillWagner

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1/2 x 20 thread takes up apx .050 per revolution. 1/4 turn takes apx .012. By adding a quarter turn, .012 is taken out of the total travel of the injection stroke, IIRC the lift is .232, so, if you only allow .220 of lift in a spot that has .232 built into it, it takes a bit of time, but something will go away, the weakest link, the crimp, push tube, cup, cam follower pin/lobe/roller, something. What happened in cylinder is not the result of the injector setting, it was either just time for it to happen, I think you said the engine had unknown mileage, or an issue with an overhead set. A cross head WAY out of adjustment can do this, 1 valve will open sooner/farther than the other and contact the piston, you see the reliefs in the piston crown? There is not much room there when the valves are open and the piston is coming to TDC, injection happens when the piston is at .266 from TDC, some say it's positive end of injection, others start of injection, that's another story. In a nutshell, the valves open and close in the last .250 or so of the stroke, so, if there is an issue with the overhead, at 1500 RPM, the valves on one cylinder will open/close apx 12 times per second, so there is a possibility, if things aren't correct, for any valve in any cylinder to make contact, weather it is by .0001 or more, with a piston, 12 times per second until something clearances itself.

This is one of the reasons I did not cover cross head adjustment in the overhead set post, it is very easy to get things wrong and cause issues.

What happened to your engine is/was a fairly common thing, can't tell you how many engines I fixed or replaced under warranty from that failure, you got lucky, worse case could have been an engine that about cut itself in two. Hard, next to impossible, to tell what went first, an intake or exhaust from the damage. If you repair the engine, be diligent on your inspection, I am going to assume that pieces went throughout the engine. ANY cylinder that has any debris in it should be replaced as well as the rods. If the crown of the piston is damaged and pushed into the liner, it is junk, the liners are cast and don't like pressures other than that from the combustion process. I do not recall if you are running the aftercooler as well as the CAC, but if you are, the core should be replaced, you will never be able to get all the little pieces parts out of the core fins. If you just have the CAC, remove it and take it to someone to have it cleaned, the pieces most likely migrated back into the cooler, they are there even if you think you don't see them. Rods need to be Big Cam rods, they use the 12 point bolts rather than nuts/washers. The oil delivery to the upper bushing is timed different, they are drilled off center. Small cam rods fit and will work for a time, but your engine has more than standard fueling and cylinder pressures, a rod from a SC will, in time have the upper rod bushing start to score, then attach itself to the wrist pin and then bad things happen, you will need to start looking for another engine. Heads are the same from NHC to NTC, you just need to make sure the little hole on the head casting under the rocker box is plugged or you will have massive amounts of blow-by, it will be because the manifold pressure enters the crankcase thru these holes, they go directly to the intake port. Tap them for 1/16 pipe and just plug them.

If you need anything, call me, more than happy to help out.

Oh yeah, you'll probably want to have the injectors looked at. All those little bits of metal swirling around in cylinder have a tendency to damage the holes in the cup, they like to get ovaled or pinched shut. Would suck to put things together and then take it back apart.
 

WillWagner

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I also thought of something, a Jake issue can cause this type of failure, but only if it is a mechanical failure of the brake components, like a broken actuator spring, the one that makes the foot that actuates the crosshead, so, that might be something to look at. It takes an arbor press to disassemble the brake piston. If it was set tight, it will cause a miss on the tight cylinder, or, if they are all tight, as soon as the engine gets some heat in it, it will die like you turned off the fuel but after sitting, it fires right up and will run until the valve stem grows from heat and the cross haed and actuator make contact again. Never seen an in cylinder failure from that, only a big tow bill.

Since there is only 1 exh valve head gone and you have a dual valve actuated crosshead, I don't think that is the cause, but it is something to check and easy to do before you re assemble
 

simp5782

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Got it to Profo's late last night. Started on it about 9 this morning on and off thru the heat. He's camping so it's an alone job for now. Cab pulled. Engine and transmission out. Engine taken apart liners pulled.

Ended up steam cleaning the block really good. It needed it since I will probably paint it before it goes back in. Steam cleaner is handy except from burns on holding the wand. Plastic does get hot apparently.

All the rod bearings looked fine. It did smoke 2 pistons on 5 and 6 but the crank is in good shape. Installing 6 new rods for the heck of it. All stamped USA and not Brazil or UK.
Going to carry it back to Memphis for reassembly there and run it on the dyno before it comes back to get reinstalled. Should be fine.

Then again I did come across a KTA600 for next to nothing. I just dont think I can fit 19 liters into a 5 ton. But it would be cool
 

simp5782

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Rebuild is already under way. Should be back rolling this weekend. just waiting for injectors from promos in Texas to get built
 

tennmogger

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Wes is the Energizer Bunny of MV's. He even made time to evaluate, load, and haul an LMTV for me yesterday. Thanks Wes!! Great job!
Bob
 

Floridianson

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Uncle Jim's mobile home, high colonic clinic and use MV emporium. Walk in, ride out cleaned out. Payment plans to fit any cleaned out donkey. Or motto is "We will clean you out one way or the other".
 

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