quote:
Originally posted by captaintobeys:
The top ones look the same wear wise. The are not groved. Is there a set of fully groved ones out there. 3/4 Groved?
I'm a bit concerned by your description of the bearing halves lacking grooves as "the top ones".
I'm sure the bearings were installed properly, but please humor my over-cautiousness, I'd like to clarify what top indicates!
With the engine sitting upright, carburetor on top, oil pan on the bottom, the "top bearing shells", i.e. the ones lodged into the main saddles, should have grooves. The lower bearing shells, i.e. the ones lodged in the main caps, should be the smooth ones. Else there's no way for the oil to flow from the block's oil passage and into the bearing/journal clearance. In regards to deciding upon half grooved - 3/4 grooved - fully grooved bearings, I'll make these comments:
The purpose of a fully grooved main bearing is to supply oil to the rod bearings throughout 360 degrees of the crankshafts rotation. This at least doubles the amount of oil flowing to the rod bearings. This accomplishes the same thing as a cross-drilled crankshaft or grooved main bearing journals, but it was less expensive and didn't weaken the crankshaft.
Up until the advent of 0W and 5W oil, whenever you purchased a performance (tri-metal) bearing kit for the 351C it came with fully grooved main bearings, including the tri-metal bearings sold over the counter by Ford. It was the introduction of the thin oil viscosities that motivated the bearing manufacturers to stop manufacturing fully grooved bearings. With the thin viscosity oil, the groove in the lower half of the bearing acts like a rain groove in a tire tread, it channels the oil wedge away from the bearing surface. This is not a problem for 20W50, 15W40, 10W40 or 10W30 oil.
So my advice: if the engine is set-up to use oil with viscosity ratings of 10W30, 10W40, 15W40, 20W50 ... I'd use fully grooved bearings. If the engine is set-up to use 0W or 5W type oils, I'd use the 3/4 groove bearings from King Bearing.