[birdsandgoats]

I pulled the oil pan on a customers engine to fix an oil leak and found much more . The pan had lots of copper in the bottom. And I looked for the problem and found the #4 main bearing was wiped out . The rest of the mains and the rod bearings were not great but not as bad . This engine had been running for about 10 years and no problems. The person that had this engine in the car a few months ago had tried to fix the oil leak . When he had the engine out and pan off thought it would be a good idea to put a set of bearings in it at this time. The old bearing were not bad when taken out . He put in a set of clevite 77 bearings in it . It has only had about 40 miles on it since . The engine is a 496 with Eagle 4.5 inch stroke with 3 inch main crank and Eagle rods with ross pistons . I have checked the oil passages to #4 bearing and the ones in the crank a they were free of anything. Both sets of bearings were standard size . Any ideas?

[Tom Vaught]

I saw this deal once before when a builder installed a rear crank seal and the rear seal reduced the crankshaft end clearance. This lack of clearance was enough to cause the #4 thrust bearing to not get the oil it needed on the thrust surface.

Was the thrust surface bad or the actual crank to bearing surface bad?

Tom V.

[Gary H]

There's a couple of possible scenarios that come to mind. The first is that he went from another brand bearing to the Clevite bearings and it resulted in tighter bearing clearances. My experience when checking bearings is that Clevites run thicker than say Sealed Power or Speed Pro brand bearings. If the engine clearances were tight before, and he went to Clevites, it may have been too tight. Also, Clevites don't have the grooves on the thrust surfaces of the bearing like Sealed Power bearings do. May have caused an issue too.

The second possibility is that he just simply got a bad thrust bearing that was manufactured poorly and caused the issue. It's best to mic all of them before installing. I've run into this several times with rod bearings.

Also, thrust wise, the new bearings could have been too tight. It seems like half the Pontiacs I assembled have to have the thrust bearings sanded for extra crank end play clearance

Lastly, I'd really check that crank for straightness after the engine issue. It could be bent.

[birdsandgoats]

The thrust surfaces were good hardly a mark on them . The surface of the crank is not bad except where the copper has welded to it

[Scott Stoneburg]

Were the clearances checked with thw new bearing? Coukd have been too tight. Like previously mentioned. Different bearing manufacturer have different bearing thickness.

[STEELCITYFIREBIRD]

Perhaps the bearing shell/s did not seat correctly in the block?
Why?
Scraping when slipping them in?
Other foreign material behind bearing shell/s?

??

[lust4speed]

I'm learning to hate current production of main bearings, but Clevite's have been the most trouble free for me. You probably checked to make sure they didn't slip a .010" under bearing shell in the bunch? Looks like the bearing went through a grinder and think it might be hard to get that uniform of wear without the complete shell being wrong.

[Cliff R]

I can remember two times during engine assembly (dating back about 40 years) that one bearing shell in the box was .005" thicker (boxed incorrectly). For that reason I use a 0-1" ball mic and check all of the bearing shells when they come out of the package........

[steve25]

I have heard of that also Cliff, but I can't see how the Crank would beable to spin in this guy's case!

Something is for sure odd since his thrust surface itself looks fine!

[johnta1]

What block casting?

I'd check the block under that #4 main to see if it has cracked where the galley hole to cam tunnel is and around there.
(also check crank when out for cracks there)

[grandam1979]

Cliff the bearing you found miss packaged was it marked correctly on the bearing it self?

[birdsandgoats]

both shells were stamped as STD

[NeighborsComplaint]

Back of the bearing shell may have had some corrosion and rode too high in the saddle. Modern thinking may disagree, but I have always scotchbrite polished the backs of the bearing shells for best cotact with the saddles.

That said, I would have expected the other bearings to also show signs of partial contact with the saddles though as they were all replaced from the same package.

[steve25]

Well one thing you can do is to get some plastigauge, then fully dry off the number 4 Crank journal and then dry off and move number 3 Bearing into the number 4 position and torque things up with the plastigauge in there and check for whatever you may have for clearance .