on what seems to be alot of the d8h and k's im looking at, they either have just had a headgasket or need a headgasket, does the aftercooler help much with the "popping the headgasket problem".....was there many aftercoolers on the 8k's before 1980 as std equipment, or was earlier ones prob. added on later on
The after cooler simply cools the air after it exits the turbo. Head gasket problems are often ( not always) liner pertrusion problems, in the counter bore blocks where the ledge in the block that holds the liner cracks letting the liner down so the head gasket won't seal often sending exhaust gasses into the water jacket. Over torqueing the head bolts tring to get the head to seal just causes more problems. Spacer plate engines need a flat block to set the liners on so they are even and create a good seal at the gasket. Liner pertrusion or height is the key, if the liners are not right you will have problems.
The other big problem when the K series came out was that the mufflers were mounted under the engine hoods and they created massive amounts of heat under there. As I recall Cat came out with the retro kit to mount the mufflers on top of the hoods and that solved a lot of the gasket problems to a point. Another big issue is that the basic block was about thirty years old and started out at somewhere over a hundred horse and when installed in the K was somewhere close to 300 horses. Firing pressures went way up and the bolts could actually stretch enough for the heads to start lifting. It didn't help than any fool with a 7/16 inch wrench and a screw driver could up the rack setting. I've seen the non cooled turbo machines turn the manifolds red hot. At night they looked like monsters crawling across the landscape.