I've used many gallons of Diesel fuel that way, and the only engines that gave trouble were worn out already- - - - -the solvent bath just dislodged some of the gunk that was keeping worn out piston rings pushed out against the cylinder walls. You'll either improve things, or confirm that the engine REALLY needs a rebuild!
If you do have to rebuild it, at least you won't have to scrape as much crud out- - - - -splashing the Diesel around inside does a better job of dislodging sludge than hours spent with a brush and solvent after removing the oil pan.
Jerry
