Brand new main bearing nicked. Usable?
I'd run it just because I can't think of what would go wrong having a small nick out of the side like that, maybe if it was down in the center I'd be more concerned but that'll basically just act like a small oil reservoir if anything. Although I personally haven't messed with enough old engines to see a bad main bearing with my own eyes. Rod bearings, heck yeah those get destroyed all the time.
I could be worried I didn't get the last 7 or so visible dust particles out of my valley before putting the intake on but you gotta draw the line somewhere lol.
Nicks in bearings are not what is the problem, it's when there is a nick in the crank that you can feel rising above the rest of the journal !!! I never saw any pics of what this post is about, however, in over 40 years of building engines from Briggs and Stratons to big Catapillars and whatever is in the between,, Fords, Chevys AMC's, Hondas, Toyota's and racing Mopar big and small blocks I have see about everything that could be seen including some amature reassemble his Big Block Chevy for his power boat and installing the pistons in the wrong banks thereby getting the rod offset against the radius fillet which resulted in a trashed set of well everything in the end. I saw one 440 that someone the pistons backwards with open chamber heads and used 2 head gaskets under both heads to get the motor to turn over even. They were a set of TRW low domed pistons. I guess the guy was trying to get more compression and get the flame front under control like a set of closed chamber early heads would have done. I don't believe that engine ever ran as I got it in a boat that had a starter from an old 392 fire power with the 440 flex plate, the drive teeth did not match and it was terrible sounding. The Chevy bearings simply failed very fast polluting the engine to the point of metal getting past the pressure relief valve at the oil filter and taking out the cam bearings and the mains. Any how, I will address the issue of to Full Groove or to not full Groove that is the question! Never go with Full Groove when there is always an option. Full Groove bearings will reduce the load capacity on ANY engine which the crank must carry! There are a few listings for Chevy engines with 270 degree/ 3/4 groove lower half inserts. These will give you the best of each benefit, better oiling without loosing bearing surface to support the main. After sufficient time running, if you dismantle an engine that has been full groove, and measure the crank, you may even be able to see the ridge that will develop on the main journal from lack of support where the groove is ! There has always been the practice of cross drilling the mains which Oldsmobile did from many years on most of their engines. This is a blessing and a curse as it weakens the crank but with forged cranks it is not as big an issue as full grooved mains. The old Newtons law of an object in motion tends to stay in motion applies here as well. Fluids are object, and if moving one way will stay moving the same way. Yes even under pressure ! I know someone is going to contest this but that's fine. Go ask a physics professor or an engineer. The guys on engine masters will tell you. I haven't seen a part # listed for 3/4 bearings for any of the Mopar lately. But I did build an engine years ago, a 318, and I had tooling in shop that allowed me to manually machine additional grooves into the lower insert giving me a set of 3/4 bearings for that engine. I was very diligent with my work and I ran that engine for several years, raced it, drove it from western Neb. in the early 80's to the south valley region of Calif. and drove it and raced it there for a fair time, not too many races lost with that one, was called a liar more than once. Some people swore it was a 340 that I had altered the stampings on the block. Anyway, Scotch briting bearings is common, I would guess a many engines have been put together with a nick in a bearing that never caused any problems. I have seen engines taken apart by me and others that the bearings looked horrible. They were still running and still had oil pressure. Hell I know a guy in Bakersfield that had a piece of a valve stem seal get into the pump in his small block Ford and twist the oil drive shaft off loosing complete lube and he drove that car several miles to get it home with the lifters clattering. He made it and we pulled the pan, bearings, all of them, and miced the crank, it was undamaged, the bearings looked like hell but I put in a new of bearing, put it all back together and we drove and rode around for a couple of months with no problems. He build another engine eventually to replace the 289, a 302 with more performance additions. So Bearings are bearings, they can have take a lot more than what you would think.
