Simp's M923 Big Cam Repower

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simp5782

My safe word is Pork and Beans.
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Well she had her first test run around the country. Had a few issues but nothing too bad. Engine did fine for 6000 miles in 9 days of driving. It did run for approx 36 hours straight at one point with no issues. Did develop an oil leak on the front head and i will hand to tend to that later. I did have a rock i believe fly up and smack the oil pan causing a slight crack. Used some epoxy and it has held since.

Power wise with a load on it. Lets just say My 923 weighs in at 29,640lbs with two full tanks and all my normal carrying stuff for the road. I had 9 - 14R20 Michelin XZLs and 1 1600 XZL in the bed of my truck. With my M322 trailer that weighs 13,220lbs carrying a M1084 5 ton FMTV truck with a crane weighing roughly 23,675. I also had eleven 14R20s in the bed of it. Luckily all that weight was over the trailer axles being in the bed of the truck. I scaled out at 71,340. Doing the mileage from Adkins, VA up I-81 to Harrisonburg, VA is 190 miles and I covered that in 3 hours and 29min so about 54mph. Which i believe is pretty well given the up and down and long hills along that stretch of 81. I hate I81 to be honest with you just as bad as 77 thru West Virginia. after leaving Harrisonburg, VA up I81 to i78 and up over the Tappen Zee and into CT. I covered 443 miles in exactly 8 hours so right arund 55 mph given the hills up thru PA as well.

Not to shabby. makes me wonder why i didn't do the swap earlier. No overheating problems but it was cold however. Only major issue on the 2nd leg of the trip was a transfer case going to the grave.

As far as mileage goes 4.9 mpg as it burned 82 gallons of diesel in the 400 miles exactly from Harriman, TN to Harrisonburg, VA and I had about a 1 hour idle time with all of that in the 2 stops i had made. Not too bad at all given the weight and that stretch of road.
 

simp5782

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Your HEMTT T-case died?
Something internal is burning out. More like a needle bearing. I had some bearings in the oil when i drained it. It ran fine and sounded fine but had a noise when i let off the accelerator after 40mph. I need to bust it open. It had over 30,000 miles on it. maybe more I forget but it probably was not designed to go that long. I know it required 40w oil change every 10,000 miles. It also ran a little hot. Sometimes I would have a 240 degree input bearing temp but according to a few techs i talked to on it said that "well a HET has the same case and it towing the M1000 with an Abrams we are sure is over 240 degrees and probably reaches 300 or more.
 

simp5782

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Welp. Got the intercooler added back onto the radiator setup. Should be plenty of intercooler for the motor. Did order an N14 intake manifold and some stainless steel pipe and hoses. 4" inlet and outlet on the intercooler. The core is 40" wide (1016mm) x 21" tall (533mm) x 3in" core (76.2mm). The tanks on each end are pretty good size as well. It is a direct bolt to the radiator I have. The intercooler is rated to 26/28lbs.

Replaced a leaking turbo flange/manifold gasket. Was boosting around 23lbs. Now i am up to 25/26lbs. I also replaced my air filter that was a 950cfm filter with that of a 1325cfm unit.

I upgraded my fuel feed line and pickup tube. I made the pickup tube in the tank a 5/8" pipe and the fuel line to the injection pump being 5/8" as well. I did make the return line smaller. Out of the back of the head it is a 1/8" pipe fitting into a 5/16 long with #6 JIC fittings. I had a #6 T with the same 3/8" line back into the injection pump and on the tank return. I left the engine line alone and I used a small T with 3 fittings 1/8" pipe to #6 JIC so it is a smaller diameter return and I ran a #4 JIC fitting on a 1/8" id hose back to the pump. About as small as i can get besides putting a time in the fitting and drilling a hole in it.

Will be adding a rail pressure gauge to put in the cab next week along with the pryo. I am redoing my whole gauge panel so I will be adding other gauges as well. https://www.youtube.com/watch?v=29ykus9it-k
 

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marchplumber

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Thanks for ALL the info and pics ya post here on Steelsoldiers! Done some really cool things to the truck and ya just keep adding on!! Love the youtube vids also!! THANKS so sharing, maybe some day when I am in the area we could "meet and greet"...........

Take care and keep up the great work!
 

simp5782

My safe word is Pork and Beans.
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Thanks for ALL the info and pics ya post here on Steelsoldiers! Done some really cool things to the truck and ya just keep adding on!! Love the youtube vids also!! THANKS so sharing, maybe some day when I am in the area we could "meet and greet"...........

Take care and keep up the great work!
I get up your way to Rock Island Arsenal every so often. Maybe soon!
 

simp5782

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Well tomorrow is the day for the intercooler install. Should have it back together by tomorrow afternoon. Hopefully. I am going to be using the NHC250 intake manifold on this truck in place of the aftercooler. The NHC intake has a downward angle off the engine which would be better suited for an easy route to the intercooler. The N14 intake was an over the top entry and It would have complicated the bends and what not.

Drivers side will be a downward with a reducer from 5in to 4in off the manifold then i am going to come out with the pipe to just outside the frame width and 90 degree bend it and run it directly to the intercooler.

Passengers side should be pretty easy. It is going to be a 90 off the turbo to the intercooler and 30 degree silicone boot at the intercooler end.

I will be running the coolant line that went thru the aftercooler together hooking the 1.5" hose to the 1" hose so it can continue to circulate thru the upper radiator section on its own.

Seems simple enough. Least it did when i drew it out in crayon.
 

marchplumber

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Well tomorrow is the day for the intercooler install. Should have it back together by tomorrow afternoon. Hopefully. I am going to be using the NHC250 intake manifold on this truck in place of the aftercooler. The NHC intake has a downward angle off the engine which would be better suited for an easy route to the intercooler. The N14 intake was an over the top entry and It would have complicated the bends and what not.

Drivers side will be a downward with a reducer from 5in to 4in off the manifold then i am going to come out with the pipe to just outside the frame width and 90 degree bend it and run it directly to the intercooler.

Passengers side should be pretty easy. It is going to be a 90 off the turbo to the intercooler and 30 degree silicone boot at the intercooler end.

I will be running the coolant line that went thru the aftercooler together hooking the 1.5" hose to the 1" hose so it can continue to circulate thru the upper radiator section on its own.

Seems simple enough. Least it did when i drew it out in crayon.
Crayons are over rated!!

LOL
 

simp5782

My safe word is Pork and Beans.
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Well I guess the crayons worked this time.

I've gotta weld some lips on the pipes and paint them and reinstall them tomorrow. Worked out to be pretty easy for a change. Used the NHC250 intake and gave me a lot more room. Now i gotta rearrange all the tires involved in this big whole birds nest and test drive tomorrow sometime. Weather depending. I waited until today since it was in the 60s and suppose to be in the 70s this weekend.

Was not that hard of a job though, hardest part was unbolting and sliding the cab over. The aftercooler was touching it barely and one bolt would not come out otherwise. With the small cam intake though I have lots of room to work in there now. That aftercooler was pretty bulky and heavy.

One picture looks a little weird but its just a hood clearance view. I have a good 4 to 5 inches to spare on the overhead.
 

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simp5782

My safe word is Pork and Beans.
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well got her back together this evening with the pain in the butt rain all day. She pulls pretty good. Still getting around 24lbs of boost when i put her to the floor in 15th gear. I will be installing the pyro meter tomorrow. I ordered a few other silicone hoses so I can delete that nasty 90 off the turbo as well as that little rise on that hose fitting. Siliconeintakes.com has some pretty good hose selection. They are sending me a 3.5" to 4" 90 degree and a 30 degree hose to replace that side. Should work alot better. With the new 1350cfm air filter I can really feel it pull.

Tomorrow I will be installing the pyro, intake air temp gauge, and a digital dual display air pressure gauge. I am in the works of having a new dash board made so i can re position some stuff. I went with Hewitt Industries gauges that are 24v gauges. https://hewittindustries.com/product/1600f-pyrometer-gauge-kit/
 

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Jbulach

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Cant you clock the turbo 90 degrees to the passenger side and eliminate one of those 90’s, and the 30 degree?
 
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simp5782

My safe word is Pork and Beans.
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where did you get that intercooler,cant find this model
Is it a RG31 MRAP type radiator/oil cooler/intercooler setup. You would have to source something to make it fit around that big mammoth radiator in the M915 series trucks. There is not too much to work with.
 

akita91

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ive read all the mods that you did in your 923 and it looks so dope.swapping that engine + all those extra things.i wanna do the same :D doesnt cost fortune but makes hauling better if i ever get to :D
What would be the best bet to match 70-75mph,change to 7155,some manual,or newel allison like 4560 or so.
 

simp5782

My safe word is Pork and Beans.
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ive read all the mods that you did in your 923 and it looks so dope.swapping that engine + all those extra things.i wanna do the same :D doesnt cost fortune but makes hauling better if i ever get to :D
What would be the best bet to match 70-75mph,change to 7155,some manual,or newel allison like 4560 or so.

Drop your gear ratios from 4.90s to 4.30s or 3.90s would be the cheapest bet. It is a common axle found in big truck junk yards. Or go to a 12R22.5 maybe.
 
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