Simp's M920 build thread

simp5782

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Haven't done much. Just situating things. Spare parts storage. Etc. Moronic this 920 has 4 different types of U joints on it. 9c jackshaft, 1810/9c main shaft, 1710 interaxle shaft and 72c front.. Pfft. All seals for everything on the truck. Few brake valves, main line parts...


Changed the idle to 700rpms. Need to bump the governor springs tomorrow. It is set at 2200 at the moment. Going to add another 2 shims to get it to 2450/2500. With the 12R24.5s she's at 58mph at 2200.

Put more miles on her. Had a brake locking issue. Believe that is fixed now.

Put her on the scale. 32,520 with only about 30gal of fuel on board.
 

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simp5782

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Installed a digital rail pressure gauge I bought years ago that I just recently found amongst crap in a closet. Winters #DPG225. It can do PSI up to 15,000,


Picked up a hose reel at tractor supply that was on clearance with 75ft 3/8" hose for $50. Put a shut off valve at the tank that feeds it with air.

Installed Axle vents with DOT hose.

Auto drains on the Wet tank. Installed parker turn valves on the rest of the tanks.

Did some test runs. 255/260 rail pressure and 31lbs of boost

 

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simp5782

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Dumb question: What does a rail pressure gauge measure? What is rail pressure?
Pressure the injection pump is putting out to the injectors.

I have a gauge for driving habits. I can keep my foot light while feeling it pull. Saving fuel. Also helps when driving in hills at night to know when you are going uphill and you can't really tell.
 

JohnJuan

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So what is your rail pressures with the new button and slight adjustments for the 400 BC and your ETG's? I'm getting ready to tweak my 2009 full rebuild M915A1 soon and I'm following this regularly.
 

simp5782

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So what is your rail pressures with the new button and slight adjustments for the 400 BC and your ETG's? I'm getting ready to tweak my 2009 full rebuild M915A1 soon and I'm following this regularly.
I am at 260 rail pressure with #10 button. Egt is max at 780 empty truck post turbo. Truck weighs 33,000 empty

Ive got a 00 button on order
 

simp5782

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Put some miles on the old girl. Went out to my yard. About 9 to 10in of snow. She didn't really like it. Even with the front locked in. Had to go take care of some animals and figured I would make sure the chains I have fit right since 11R24.5 and 12R24.5s share chains. Cams all worked. I've got 1 pair of dual chains for the front tandem and 4 total single chains. Will have to find some for the 445s on the front if it gets too crazy

I did split the air system for the rear and front. Front its own air switch so it doesn't have to be locked with the front tandem. And vise versa.

I have 1 automatic chain setup that I haven't installed yet. Waiting for the other one to show up before I put em on the axle.
 

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simp5782

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Welp put some 2000mi on it this week. Safe to say the motor was rebuilt to a 400hp motor. She is pulling 35lbs of boost loaded at 80,000. She holds hills quite well also. If she had a higher top speed to start the hills and mountains with she would walk right up em.

Comparisons on hills is the 915a1 at 65k gross would hold a particular mountain at about 45/50mph. I've got a video of this on my page. The 920 at 80k was holding 40. Compared to a bone stock 916 grossing around 52k was at 42mph. This is on the same mountain grade. The cat does allow alot more power thru it. I am easily able to start off loaded in 7th gear. So she is quick to get up to speed.

Only one hiccup so far and that was a blown keyway seal on the accessory drive. This is nothing by silicone behind the nut and washer. It was a pretty good leak. As in rustproofed everything underside. Got to a parking lot and replaced it since I had a spare and my puller with me. I did end up screwing up and nicking the radiator with the fan and it sprung a leak or 3. But with some black pepper, and a aluminum welding rod I was able to get them to stop.

Got it all put back together and down the road I went. She is averaging 4mpg at a 54mph average over 900mi.


Axle temps are running under 140 degrees. Transfer case is showing 78 degrees. Highest rail pressure I saw was 237.

It is wise to note that on an accessory drive seal on. Big Cam 1 or 2 motor the v belt drive pulley and accessory drive is one piece so you must pull the fan to have enough room to get it all the way off. On a Big Cam 3 in the 915A1s and some first gen trucks the belt drive pulley is bolted to the accessory drive so it can be removed and the accessory pulled off without removing the shroud or fan.

The puller I used will work on Small and Big Cams. I got it from a oreilly. EVERTOUGH 67015. You may need 5/16, 3/8 or 7/16 bolts they used them all different types. Me I use a 5/16 all thread with a jam nut and washer. I then run the bolt thru the pulley to the backside against the timing cover and I sneak a nut on the backside with some pliers. Then jump the starter to spin it around to reach the other side. You do have enough room to get a nut in the backside. All and all it's an easy job. Around 2hrs to do everything.
 

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Acoustik

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Lots of good info here. Just starting to rebuild my 920 and you have given me a lot of ideals. May need to contact you for more info and parts if thats ok. Thanks simp and keep up the good work!
 
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