I have the sb400 out of the truck for a new oil pan and pan gasket. It's been leaking pretty bad for a while so it's time for a new pan since the old one is dented pretty good which I think is the reason for the leak. I thought the rear main seal was leaking too, but everything in that area looked pretty dry. That pan seal leak must have been worse than I thought!

Anyway, while the pan was off I got a look at what the past 20k of truck use this engine has done inside. Everything looked great. The cam lobes all appear to have nice wear patterns, the piston skirts still have prominent machine marks and the cylinder bores still have visible crosshatching. No metal is discolored at all.

Since I already had new front and rear main seals, I figured I should install them. When I pulled the rear main cap I found that the bearing had one noticeable score in the bearing. The crank journal is nice and smooth, no scratches. I'd say that about 30% of the dull tin coating on the bearing shell was still there and I didn't see any further signs of a lack of oil, heat or other damage. The score in the bearing is deep enough to catch a fingernail on. I'm guessing there was a piece of crud in the oil passages in the crank when I first installed it that must have gotten passed through the bearing.

I also pulled the oil pump. The pump cover to impellers clearance was a little loose so I polished down the pump body sealing surface and tightened up that clearance a little. I see it is a good old Melling pump and it had little to no wear inside. It was new when I rebuilt the motor of course. All the pump gear teeth look great, it doesn't look like any junk has passed through the pump. This all leaves me with two questions:

1. with just one score in the bearing and none in the crank, should I be okay to run as is? (I did not inspect the other mains nor any of the rod bearings, oil pressure is 50-60 cold, 40-50 hot).

2. I did not index the pump gear teeth so I'm not 100% sure I got the gears back in the pump in the same orientation as they were originally. Should this matter? One book I have when talking about how to blueprint an oil pump says to mark the pump gears so they can be returned to the pump in the same orientation to one another, though I can't imagine how much difference it makes.

do you have any pictures?

While it is out of the truck and you have noticed a scar on one of the bearings I would check the rest out and possibly replace them.

if the score is in line with the oil hole it was probably a POS in there, probably got flushed out. I'd probably go ahead and run it since it's a known good bearing that fits right and gives the right thrust clearance. But I would probably have a look at at least one other main just in case.

If you look at the end of the gouge, you may see the POS that caused it. The bearing people call this property of a bearing " embedability". Sometimes there is a "moon" encircling the POS. The bearing did it's job , and sounds like it has lotso life left.

I assess reusing a bearing by guesstimating the % of surface wear thru each overlay. If you aren't thru any overlays and all you have is a scratch, run it dude.

Count how many spurs or teeth each pump gear has (actually called an element). If different quantity, retiming is moot.

Some pumps have diff quantity. It's done to gain a mechanical advantage.

I wouldn't worry about timing pump gears back. Most of the losses in a pump occur at the housing clearance.

Edit: don't try to get the pos out of the gouge unless you can feel it. Then extreme caution with a knife tip, then dress it down with your fingernail.

Mike calls those scratches "oil retaining groves" should not be a problem if it is that small.

Mike calls those scratches "oil retaining groves" should not be a problem if it is that small.


Yep, I had a similar scratch turn up in one of my mains upon inspection. That is exactly what Mike called it. http://img69.imageshack.us/img69/2087/bearing1eb5.jpg