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I4 or I6 counterflow / u-flow engine options

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  • I4 or I6 counterflow / u-flow engine options

    Hello all:
    My name is Robert and I'm new to this forum. I hope the post is ok here in this area. I imported a Mercedes Unimog 404S from Europe a while ago. It only has 12,000 kilometers (approx. 8k miles) on it. A while ago the engine started losing power and I started looking into it. From the long time not being turned over the cylinders and top of the block (cast) started corroding. Repairing that engine will require to bore it, deck it, new pistons etc - you get the picture. Lots of $$$
    As an alternative to rebuilding the current engine or find a rebuilt one (that has most likely been sitting for a while too, even though dry) I'm also looking into swapping it for something else. The main problem is the very limited space in the engine. The stock engine is a 2.2 liter I6 with a counter-flow head. Intake and exhaust are on the passenger side. I'm looking for an I4 or I6 that is the same setup and should be 110-120 HP and somewhere around 140 ft-lb of torque. An engine that comes to mind is the 2.5 l AMC straight-4 but it has the intake and exhaust on the driver side from what I have seen. I might be able to use that engine and just rotate it towards the passenger side but I'm sure there are other options out there too. The above HP and torque limitation comes from the transmission - it can't handle more than that. Any ideas for engines to use are greatly appreciated.


  • #2
    Welcome Robert, Unimogs are really cool project vehicles.

    Being a Ford guy, the 300 (4.9L) inline 6 comes to mine. HP is within the range you specified. Torque is a little higher, but could be limited with a smaller carb. The real selling bonus is that these engines are cheap and plentiful, and they have the reputation for unbelievable reliability and low end torque. Engine layout is similar to your Mercedes with the intake and exhaust on the passenger (right side) of the engine. There are some other displacements from the same family, like the 240 cuin I6, but the 300 is the newest and later models were built with EFI up until 1996.

    Click image for larger version  Name:	lZr4mUC-1.jpg Views:	0 Size:	277.9 KB ID:	3251
    Last edited by Digger; 04-26-2022, 12:18 AM.