[spareparts]

I used to work for a street sweeper manufacture and we used 6.5's in some of the trucks(they didn't hold up too good), we had issues with blown head gaskets and stuck injectors( These were N/a models). They took one of the heads to the fab shop and cut it up in 1" increments to look at the cooliing passages, they were some of the most restrictive, tight turn, full of slag coolant pasages I've ever imagined. We were getting surface temps of 325 right around the injectors under hard load( those trucks had two speeds, sweep and wide open, 45 mph). The injectors were sticking open under load from the excess heat and when you backed out of the throttle it would hydraulic the cylinders kicking the crank out the bottom. We initially had the temp sender located on the heads and couldn't get the temps lower than 225, GM told us to relocate the sender to the block, some fix! I heard one of the dealers had replaced the antifreeze with some type of special coolant(can't remember the name but its distributed by Mack Boring) that had superior heat transfer ability. That dealer had no more problems with head gaskets or injectors. After GM sold the tooling to those engines to AM General, they suppposable retooled everything and got them to hold up better(had to pass Military spec), Marine Diesel USA is selling those motors up to 425 HP in a supercharged version, they must have found something right.