Does anyone know why CAT used the spacer plate between the head and the block on some of their engines? It seems like another place for more problems to develop.
I think it was suppose to make less of a chance for cracks in the top of the block.
Plus it saves the block deck from erosion.
That makes more sense. So you do not have to machine any on the block, you just replace the spacer plate, unless you have to cut counterbores. If done right it shouldn't cause trouble. How do liners sink anyway?
The liners bounce up and down one molecule at a time until measurable wear occurs to the counterbore.
Which is normally taken care of by cutting block for shims. That usually ends that issue, even Cummins starting with N14 decided it was the way to go. Fretting in parent metal block deck/counter bores has always been a issue.
The counterbore issue didn't seem to be that much of a problem in the D342 engines used in the D8 engines until the D8K. I hade kind of a fleet of junk for some years that included 13A, 14A and 46A all with old age syndrome. I've at a minimum had the heads off or done out of frame overhauls without much problem with the counterbores. I got the worm holes in the liners more times than leaking counterbores. We always had them checked and machined at rebuild but the engines were usually torn down for other reasons than exhaust in the coolant. The D8K models with the counterbores seemed to be the mass starting point of the problems that I experienced. The bump in horsepower seemed to bring out leaking issues with exhaust in the coolant. It wasn't long into that run where I saw the plate engines. I drilled and tapped a D8 radiator cap for a pressure gauge so I could prove to people that compression was getting into the coolant when I did appraisal inspections.
Those D8K’s really were better off in the hands of owner drivers or really good operators that knew how to start them up and shut them down properly.
It didn't do much to prevent having to still cut for shim's, because the flange still wore into the deck. At least there was much more material to deal with than with a counter bore. Too much trade offs in the design world of those engines, simple ways they could have made all that less of a problem, but costs $ to do so.