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Swapping a Cummins 290 into a M939 series truck

Vintage iron

Active member
1,123
16
38
Location
Falmouth Ma.
Just finished putting the Turbo Big Cam Cummins 290. In my M936 Wrecker. My good buddy Martin Cox was selling his wrecker and I couldn't let it pass. I took the 250 Cummins out of the wrecker and put it in my old M923 that Capecoastie now owns. This is a very difficult swap, I would not recommend it for the average mechanic. I have about 250 hours into the swap.
Made a new front motor support mount, relocated the oil filter, made new 5" intake, new 5" exhaust, new expansion tank mount, new power steering setup, 1 3/8 body lift, new fan mount bracket, new dual fuel lines, rebuilt the the wrecker injection pump and had to make a ton of new hoses and lines.
 

162tcat

Active member
710
46
28
Location
Washington
The easy method is to just swap the turbo parts over and do the dual fuel mod. I run mine at 335 spec and tow heavy with no issues. So how does the wrecker pull now with big cam power? Are you going to turn it up more?
 

Vintage iron

Active member
1,123
16
38
Location
Falmouth Ma.
The benifits are worth the work. The motor is pushing 350 HP and 1150 Ft lbs of torque. Plus it has piston squirter, huge oil cooler and Jacobs brakes.
 

Vintage iron

Active member
1,123
16
38
Location
Falmouth Ma.
I am running the stock Allison 5 Speed. My Customer Steve in Ct. Has been running a 450 HP Big Cam in his M929 and runs 1600s for two years with out issue.
 

Vintage iron

Active member
1,123
16
38
Location
Falmouth Ma.
I want to Thank all the guys that helped me out on the swap, Martin Cox, Greg Smith, His brother in law Andrew, Glenn and his son. Also want to thank my new Mechanic Tim, it is great to have a fellow Marine working in the shop with me, Oorah and Semper Fi.
 
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