In reference to my 77 model Ford 351M engine. I installed a crank kit. It came with .030 over bearings. I had a machine shop recondition the rods. The man told me that the reconditioning would have no effect on the rod bearing size. After assembling the engine, I was letting the engine warm up so I could adjust the timing and bleed the coolant system. After it idled for a few minutes, It started making a clacking noise. Not a whole lot, but enough to make me concerned. I removed the oil pan, and found that every bearing was already showing wear marks. The marks were only visible. There was no groves or roughness felt. But one bearing was different. It did have a groove worn in it. I had only let the engine idle for about 10 minutes. There is no wear at all on the crank rod journals. I then went to the Advance Auto website. They had a set of .030 over bearings listed. But then I saw a set for a Windsor engine, that was 30x2, which the description stated that it was .030 undersized: .020 rod bore. Does that mean, that the rods being reconditioned, does make a difference on the bearing size? I did not see a 30x2, listed for my Modified engine.

 

How clean did you keep things when you assembled it ? Did you use any assembly lube ? Sounds like it has grit in it .

 

you don't mention a couple important things..what were your bearing clearances during install and what was your oil pressure during the warm up period?

 

Undersize is the measurement of how much of the crank was ground away in order to recondition it. It involves the inside diameter of the bearing.
Oversize is the measurement of how much of the rod journal was cut away to true up the hole. It involves the outside diameter of the bearing.
A 30x20 rod bearing would be .050" thicker than stock.
If there is a groove cut in the bearing it was most likely caused by foreign matter such as dirt, grindings or even a burr left on the crank. Is it in line with the oil port?
There will be some minor polishing of the bearings during initial start up so I wouldn't worry too much about that. I would be worried about the groove in the bearing and the knock. I would suspect the block wasn't cleaned well enough and something didn't get the oil it needed. But it is hard to see from here.

 

Normally when rods are reconditioned, the cap has a couple of thousandths of an inch ground off the mating surface. The cap is then reinstalled and torque to the proper spec. Then the rod big end is honed to the original spec, not oversized. A regular set of oversized bearings will fit with no problem.
If the big end was oversized by +.020" a standard OD sized bearing shell would literally fall out. There would be absolutely no crush.
I think your problem is somewhere else.
Did you use assembly lube and did you prime the lube system before initial start up?
Also, how clean was your assembly area?
It's normal to see what I would call buffed areas on a bearing after its been run but grooves are a definite no.

 

I would perform some exploratory investigation. If you still have the oil that was drained out of the pan, look at it closely and see if there is any sand, grit, metal filings or other debris. I would also cut the oil filter open and examine the filter media, there really shouldn't be anything in the pleats.
I would also pull the valve covers and look around the oil drain back holes.
If there are no other problems found I would get a new rod bearing, reassemble the engine, get a good mechanical oil pressure gauge, prime the lube system and start it up.
Just for peace of mind you could plastigage the bearing clearances.

 

My work on assembly was very clean. If it was caused by dirt or a foreign object, would not there be a mark, also, on the crankshaft journal? The journal looks unblemished, as if it had not even been started yet. I also felt, with my finger, up around the topside of the journal where I could not see. I felt nothing but a smooth surface. As to all the questions about assembly lube, all I have ever used is STP Oil Treatment, as recomended by a mechanic many years ago. All of the bearings have the minor polished or buffed spots, as you all call them, with the acception of the one, which actually has the groove in it. And the groove is all the way down into the brass. I was very careful, removing the rod cap, so I would not lose anything that could possibly been in there to cause the groove. There was absolutely nothing there. The groove is not in line with the oil port in the crank, but, it is in line with the notched area, in the bearing, that locks the bearing into the rod journal. Could there have possibly been a burr in the bearing itself, that became dislodged and caused the groove? I would think that with the bearing being a softer metal than the crank, that,that would cause a groove in the bearing and not one in the crank. I did not check the bearing clearances. I should not have had too, I bought the Crankshaft and bearings as a kit.

 

Not necessarily, that's one of the functions of this type of bearing. Its bearing surface is much softer than the crank journal, so the relatively easy to replace bearing shell takes the abuse as opposed to the crank journal. It sounds like the bearing was doing its job.
I agree, you shouldn't have to check the bearing clearances but mistakes can happen. I just like to double check to be sure.....that's my OCD kicking in .

 

I have a magnetized drain plug. It did have very little metal material on it. I suppose that was from the one bearing being grooved. Also, something odd I noticed, there was some fiber type material in the oil pick up screen.