Oil starvation on a 425

[alan4video]

A friend of mine has just rebuilt a 425 with new standard size bearings, rings etc. Every thing was checked carefully before assembly and he has rebuilt many engines before. The engine lasted about 50 miles before making the most awfull clattering noise with visible movement of the crank pulley. We pulled the engine and found all the bearings trashed. It was suggested he used the wrong size O ring on the pick up pipe for the oil pump. Despite a new O ring, this was split in half on dismantling. Apparently the 3/4" is for 1970 inwards and 5/8" is for earlier engines. He used 5/8" because of the tighter fit. Could this O ring splitting cause such destruction of the bearings in 50 miles?
Your opinions gratefully recieved.
Cheers.
Alan.

[cadillac_al]

The split o-ring sounds like a strong possibility. Did the oil light work? I assume he primed the oil system and used assembly lube. It's pretty easy to damage new bearings on start up. If it didn't have sufficient oil pressure the oil/idiot light should have came on at some point. I have to put a reground crank in my 425 in the next couple months. I'll be watching out for that o-ring. Good luck on getting your friends car back on the road.

[alan4video]

The oil system was primed and assembly lube used correctly. The oil light did not come on, but apparently it only takes about 4 psi to work anyway. It was run for about 30 minutes on first starting and then driven out. After about 50 miles it started to knock and within seconds was shut off. There is no backing on the bearings at all and the crank is so badly scored it may not be salvagable.
Alan.

[cadillac_al]

Ya know the more I think about it, I think the o-ring was the culprit. I don't know of any weaknesses in the Caddilac oil system.

A couple weeks ago a friend of mine was siphoning some gas from one ATV to another. He sucked and sucked on that hose for a few minutes and was almost out of breath and was barely getting any gas. I walked over to see what he was doing wrong and I could barely hear a little pin hole in the hose. Once I put my thumb over it he was siphoning gas on the first try. I think this is the same principle; a little pin hole or leak will keep the pickup from building enough suction to pick up the oil. A split o-ring is more of a leak than a small pin hole. Don't give up on it; try try again. I hope your rods aren't damaged too bad.

[deVille33]

When I start an engine for the first time, I install oil gauges at as many oil ports as I can. The 425 has two available oil ports. One just above the oil pump and one at the back of the block where you normally put the oil pressure sensor. I'd install gauges at both for the start up. After initial start-up, I'd diconnect the back one and reinstall the pressure sensor. I usually keep the other mounted under the hood for awhile, just to monitor the pressure for a month or two.
Did you pack the pump with vasoline? The shop manual makes this step because of the distance from the pick-up to the pump.