Simp's M923 Big Cam Repower

simp5782

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Aight folks, well hopefully I won't have 500,003,043 posts before the actual finish product is complete but I thought I would go ahead and show my next project since this will be a pull out and overhaul more than likely. ODO in the 915A1 says 133,000. Was a Kansas National Guard truck. At that mileage the big cam could be just getting broke in. Tried a test run. Injection pump is puking from the bottom of it. Going to see what is leaking hopefully tomorrow. Engine sounds like it has good compression.

Big Cam III rated at 400hp/1350ft/lbs. At the current moment it has an Untagged Schwitzer turbo on it. I am going to assume it is a 4LHR. I am going to plan on some upper range injectors. some pump work. HT4B Holset turbo and dual fuel line mod. Should see some pretty respectable numbers out of it.

I plan on using the front mount cross member from the 915 in my truck. Being that it is 33 inches across on it with the support plates behind it at 33 3/4" across should fit just fine so that will save up a lot of the front mount fab time that some folks have said is a problem. The rear mounts are already set up from the CAT transmission install. Everything else should be pretty easy going compared to my last project.

This truck sat in south texas for a few years so it was covered in barbs. Bad enough that my crowbar cant break thru them.

https://www.youtube.com/watch?v=cUpSJUBt6rs
 

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74M35A2

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The race is on.

Your swap will be a good one for the board to learn. Big Cam turbo engines are awesome, plentiful, and low cost. You are replacing an engine the same displacement and block style, so hope it goes well.
 

sandcobra164

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I can't wait to see. You gave Clint about a year of lead time. Hope you both have upgraded transfer cases before the race or tug-of-war takes place. It was nice to find out that the M915 front mount will be an easy swap. I don't think I'll ever need Big Cam power but if my one of my boy's avoids braces, I may talk myself into it.
 

simp5782

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I can't wait to see. You gave Clint about a year of lead time. Hope you both have upgraded transfer cases before the race or tug-of-war takes place. It was nice to find out that the M915 front mount will be an easy swap. I don't think I'll ever need Big Cam power but if my one of my boy's avoids braces, I may talk myself into it.
I am headed to Profo's sometime in the next week or two is the plan to do all my trailer hydraulics and HEMTT case swap. Just got some movements going on at the current that is delaying that.
 

74M35A2

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10-4 on braces, both my kids have them, there goes $10,000.

So the Simp855 didn’t fire in the test video. Mine did. If he goes from non-running to installed and running well, before me, I’ll have to hand it to him. My trans will still shift faster though !!! Bring it bubs....
 

Ford Mechanic

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That cross member looks very familiar, I bought one off a fellow member who claimed it was a cab mount for a 923. Now I know what it was for! Too bad I gave it away last year at the Denton rally I belive, do I would have given it to you.

Sent from my SM-G900V using Tapatalk
 

simp5782

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That cross member looks very familiar, I bought one off a fellow member who claimed it was a cab mount for a 923. Now I know what it was for! Too bad I gave it away last year at the Denton rally I belive, do I would have given it to you.

Sent from my SM-G900V using Tapatalk
That is why i wanted the whole truck. I paid under 2500 for the whole truck and that included the cost to get it here from south texas. I wanted a few of the other parts on it.
 

simp5782

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Took the injection pump off and got it taken apart and it is sitting in some cleaner till i get back. Took the cab off to make this process alot easier. M915 cabs only have about 8 things that need to come off to remove the cab. Way easier. My experienced wrecker operator will be up the first weekend in May to get the swap done. It will take about 3 hours for me to have the engine/transmission out. Then a few hours swapping the bellhousing and transmission over and then back in we go. Then drill the frame for the front mount. Should be just a weekend thing.
 

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74M35A2

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Did you get a successful test run of it yet? I think your vid only showed cranking. Would hate to see you do all this work, and the engine's a dud, knocks, mixes fluids, or smokes like a steam locomotive.
 

simp5782

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Did you get a successful test run of it yet? I think your vid only showed cranking. Would hate to see you do all this work, and the engine's a dud, knocks, mixes fluids, or smokes like a steam locomotive.
Engine spins and sounds fine. Bottom of the injection pump had a blown out gasket in the test video. You have to take it halfway apart to get to it so there isn't much point in not rebuilding it. I have a complete master overhaul kit for the engine including crank if I need it with 17:1 pistons. The one main thing I have noticed on the higher mileage 915s as We have had several in the 120 to 140k range come out at auction. All looked ratty but ran great. Gimpy even drove one back from Wright Patterson for me. I don't suspect an engine problem with that high of mileage honestly. Turbo does not have any slack and spins freely even though it will be getting swapped out that is a good sign. Big cams are cheap to rebuild. I picked that master kit with crank for $1350 from an engine parts place that had it in their stock for a long time and wanted to be rid of it.
 

74M35A2

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I want it to run good for you, so some grandpa's RV doesn't tear your pants off. Absolutely can't beat the sound or low RPM torque of massive cubic inches.

Besides the 3126, looks like that shed roof in the background could use a little lovin' there, bro...
 

simp5782

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I want it to run good for you, so some grandpa's RV doesn't tear your pants off. Absolutely can't beat the sound or low RPM torque of massive cubic inches.

Besides the 3126, looks like that shed roof in the background could use a little lovin' there, bro...
That is my neighbor's shed on the street behind me
 

WillWagner

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Just a heads up, when you swap the flywheel hsg from a SC to BC, one hole does not line up, it is the bolt hole just above the cam bore. You will need to enlarge it. I have a jig to do it at work.
 

simp5782

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Just a heads up, when you swap the flywheel hsg from a SC to BC, one hole does not line up, it is the bolt hole just above the cam bore. You will need to enlarge it. I have a jig to do it at work.
I already have the big cam I housing that mates it to the cat 7155 hooked to my small cam. I drilled it then so it will be a direct swap to the BCiii. I'll have to seal it real good so It doesnt leak

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