p m said:
The temp consideration I got from Paul Schram and a local indy shop - both say there are fewer issues with dropped liners and blown head gaskets with P38s than with D2s. It could be attributed to slightly higher level of maintenance P38s used to get, though.
I am not buying that at all. If that's true I think we would see 4.0L p38 trucks running significantly lower operating temps than their 4.6L counterparts. As far as no cooling system changes to D2 when it got the 4.6L engine, that isn't true either. Halfway through 02 they changed the front covers to delete engine oil coolers altogether and changed to a different fan clutch and began using a "D1 style" engine fan instead of the p38 style fan they had been using since 99.
As far as casting differences in the blocks, yes I totally believe that. I put a new 4.6 in a Range Rover a couple of years ago and before installing the heads I compared it side by side to the short block that had been removed from the truck. The original engine block was full of casting flash, the oil drainback holes in the valley looked terrible, etc. The new 4.6 shortblock (from AB) was far and away a better finished part, it had been cleaned up carefully before assembly, sharp edges were chamfered, I could not find any of the jagged casting marks that were everywhere on the other block, even the stamping on the crank looked better. Oh and by the way, that truck was a 2000 or 2001 model, so if the casting quality deteriorated leading up to the blocks they put in the 03/04 D2s then yes I could totally believe it had something to do with the high failure rates- but very late 02 P38 should have plenty of issues as well.