403 in a U

[1948 mm]

I am thinking about putting a 403 in U. If I understand everything correctly all I have to do is swith the crankshafts, switch the rods pistons and jugs. Just wondering if this will work before i get started? Thanks!
 

[nl00sb]

get on the pulling forums and ask Mopower hes pig into MM
 

[t.r.k.]

There are 2 ways to go.

1. Put crank, rods, blocks and heads on the U crankcase, use the U starter flywheel.

2. Put entire 403 in U, use 403 power unit flywheel and starter. May have to grind clearance for the starter in the transmission bell housing.

Either way creates problems with water return to radiator. (I solved this by using a diesel return inlet. Turned it upside down. But I was putting the 403 in a U diesel. May be hard to find, only 700 diesel Us were made.)

Another problem to overcome was the water bypass. I ran a tube up to the extra pipe plug in the U water manifold. I think some people just plug it off. If you want a temperature sensor in the return manifold you may have to be creative to make it fit under the hood.

The U radiator may prove to be marginal if you intend to work it. For a few minutes pulling it should be o.k. Mine could pull the bog in 4 th gear, but would soon boil the water. An extra thick core in the radiator helped some, but its still marginal.
 

[bp4455]

an alternative solution would be an aluminum car radiator with an electric fan. MMs tend to be rather heavy anyway and this would help alleviate that.
 

[mightymolinekid]

We used an aluminum drag race radiator and electric fan for my UB. Its all mounted in the original metal shell where the old radiator was. Radiator shop did the Fab work and turned out awesome. Bolted right up like it belongs there.
 

[Harpo]

If memory serves me correctly (probably dont), a 403 crankcase will not bolt up to a U.

Many years ago I put a complete 403 in a UB and the only thing that I had to do was grind out for the starter.

Dont remember if I had to do anything about piping to the radiator.

Harpo