She's gonna blow!

Just picked up a '91 XJ HO ($200 so I can't complain ), and on the drive Home, 62 miles, it got hot, realy hot. The entire last half of the trip the temp guage was hovering just shy of the red zone. Oil pressure stayed at around 30psi for the highway part of the trip.

My question is, could the rods be causing this? All 6 rods knock like mad at around 800rpm, some louder than others, but nothing at the higher RPM's. Or, is there something wrong else with my coolant system (water is olive drab green) ?

Furthermore, should I rip into this motor to replace the bearings and anything else that's gone bad, or just replace the short-block with a good one I have out of an '88 non-HO (difference?) ?

PS: it has 238k hard (Seattle) miles on the clock.

Thanks for any input
Nathen

It's a good thing that it was so cheap. I wouldn't have driven it that far while it was hot....because all you're doing is creating more internal damage when you do that. Things it could be: Head gasket, cracked head, water pump, thermostat, radiator and tank (cooling system), rod and/or main bearings (seizure) and a few other things could cause these symptoms. I'd say that the motor is pretty much shot...if it was knocking pretty hard at close to an idle and you drove it over 60 miles knocking and overheating.

Your pre H.O. short-block is the same block as the H.O.'s....I believe the only difference between the H.O. and the non-H.O. is in the head/intake, so you can use your short-block and use the head/intake off of the H.O. I'd definitely have the head magnafluxed and surfaced though....especially after getting it that hot. Good Luck....and good job getting a cheap XJ !
Aron