So about a month back pulling a 1000lb trailer up a 5% grade about 2800rpms my oil pressure gauge starts twitching, i pull over and notice a knock in the bottem end. i shut it down and check the oil which was full, not burnt or milky or anything like that. start the truck back up and gain oil pressure above 1000rpms so i continue driving to final destination. the oil pressure gauge twitched off and on during this last few miles.

I got the bronco home and pulled them motor to find all of the mains wiped out. some of the wear was odd in that 1 side of the bearing was worn even past the copper. I dropped the motor off at the machine shop, after they tore it down to inspect they said the only damage was to the mains. the rod bearings and everything else checked out. I am rather baffled as to how this could have happened.

history, motor was rebuilt 3yrs ago to the month its a 96 roller cam motor with a .30 bore, head rebuild, bottem end balanced, clevitt bearings and arp holding the bottom end together.

I suspect either a clogged pick up tube, failing oil pump (new meling) or clogged oil filter.

the machine shop will be getting things in order and reassembling the motor. they are as baffled as i am on how just the mains went and nothing else.
link to the bottem end pics
1994 Ford Bronco Motor teardown pictures, videos, and sounds | SuperMotors.net

 

Bizarre.. sorry about your luck. It doesn't take much of a restriction to limit oil to the bearings so hopefully the shop can find the cause or if not ensure that all oil passages are clear.. so it doesn't happen again.

 

yea they are wanting $1850 to regrind crank, replace bearings (mains and cam) hot tank to ensure its clean, hi vol oil pump , gaskets and assembly. seems steep. i may just have them do said work and i reassemble the motor.

 

If the mains went the rods did too, they get oil after the mains (thru the mains actually) Might a been softer than necessary bearings. (race bearings) Clevite makes more than one style bearing for each application. You don't want the race style in a truck motor.

 

Line bore after added ARP bolts to mains?

 

Yeah too much... A block prep costs approx. $350 and includes hot tank, magnaflux, freeze plugs, cam bearings, bore, deck, and rod conditioning. I spent another $300ish on new pistons, rings, bearings and gasket kit via summit. A quick mike check and visual inspection will tell you if your crank needs redone but it might be cheaper to source a good one on ebay or craigslist. You might not need all this so it could be cheaper. I suggest a different shop.

 

the bottom end is balanced and line bored.