903 my worst nightmare!!!!
Beins were on the subject , thought I'd add my 2 bits.
I've worked on 903s' in marine, tractor, trucks, shovels, yarders,just about anything that needed 250- 350 HP.
They weren't a bad engine just were difficuclt to work on in comparison to the 855s'.
As Steve Campbell says they could really put out the juice, I never hopped any up but my old forman told me there was not a problem getting 500 hp @ 3000 rpm and they would smoke anything around, in there day. I know a couple old truck drivers that still dream about hopping one up today, although they never have the money.
My worst experience was one we had out of a Ford cabover. I don't remember the exact reason , I think something had gone wrong in the gear train. Anyway one of the mechanics decided to change the rear cam bushing only, I ended up on it at the tail end of the job and was the one to fire it up. It idled fine and everything was looking good when I decided to bring up the RPM a bit, all went well until I hit 1800 and then the most awful ear-pearcing screach came out of the engine and the engine went from 1800 to 0 rpm in about 1/5 of a nanosecond. The entire shop went dead quiete, you could have heard a mouse pass gas, then an old boy walks up to me and says I reckon they should aught notta changed that cam bushing.
Need less to say I ended up pulling the engine and fixing it. It lived, but the owner never came up with the money for the first repair and I think it was sent off to the highest bidder. A Johnson