Unless he has dorked with the IP speed govenor I don't think overspped would be a problem. Has the block and head ever been milled such as for a rebuild or due to a head gasket failure? If too much was milled it is possible the pushrods are now too long. I believe this motor also has hydaulic cam followers. Is the oil pressure within proper range? I wonder if too high of oil pressure, say from the a bad bypass flow not opening causing problems with the hydraulic lifters?

TimK

__________________
EPA 609 & 608 HVAC Certified
_________________________________________
83' 300D Turbo - 300K + Miles
00' 1.9L TDI Beetle
85' 6.5L Turbo, GV-OD, GMC Suburban,
67' 2.5L Diesel NA - Land Rover Series IIA

Here's what you do if it's so cold your diesel fuel gels. Smear some on some toast and stay inside until it warms up outside.