hi, i was changing the rod bearings in a motor (73 chevy 350) i grenaded when i noticed a difference between the old ones and the new ones. the ones in the motor had a semicircular cutout on each bearing half, while the new ones had no cutout. seems like the bearings would get oiled from the inside by the holes in the crank, so i don't really know what the cutouts would be for. however, i don't want to put the motor together with the wrong bearings and blow it again. anyone know what these holes are for and if i can get along without them??? thanks in advance, brian
If you're talking about the groove cut into the bearing, it's for better oiling. I remember "fully grooved" bearings being available years ago for performance applications; in fact, in the early days of OHV V8s, hot rodders used to have a groove ground into the crank journals for this purpose.
not a groove in the bearing, i have those in the mains, but this is just a cutout on the edge, see the pic which will hopefully show up. thanks.
It's just a different brand from what you had before. Find someone with a "dialbore gauge" and have them measure the id of the bearing installed. Makes no difference whether it's rod's or mains. Subtract the crank dimension and you'll have the clearance. This is far more important than the design of the bearing. It's also more accurate than plastigauge.
Sorry, misunderstood you. The cutout you're talking about has no effect on oiling--don't be afraid to use them.
cool, thanks very much. last time i built the motor i wasn't afraid to use flat bottom lifters on a roller cam and i nuked the whole motor, so this time i decided to ask a question or two before i put it back together.
The cutout in the bearing is to let oil pass out the groove in the rod/cap to be slung out against the cam and cylinder walls. Frank
Earlier rods had a notch across the rod mating face that the bearing notch lines up with. It's to squirt oil up under the bottom of the piston on the opposite side. Not sure if it was for piston cooling or pin lubrication but I don't think they're in most newer passenger car rods. You don't need to worry about this one but keep asking on stuff you don't know. Frank, ya beat me. Bill
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