Quote:
Originally Posted by Tom Vaught
On the question of the extra machining on the block for the "Dual Feed Bearing" strategy. I spoke with my Block expert and also with another oil passage expert and they said that they think that the mod is a valid mod for a couple of reasons.
1) They felt that the oil channel in the upper bearing shell was not wide enough to support high rpm rod oiling to the rods with the factory single oil feed hole scheme.
By adding the second feed hole you added a lot more oil to the bearing shell/crankshaft therefore adding a lot more needed oil to the rod bearings when needed at 8000-9000+ rpm.
2) The oil groove in the upper main is only about .130" wide at the lowest portion of the groove so that would support what my associates are thinking. The bearing material is cut back slightly to about .189" at the actual bearing surface. Ed, are your bearings widened at all in the upper groove area?
3) Adding the second oil feed hole would definitely add more oil to the crank rod feed passage as it went by the second hole.
Tom Vaught
Sounds like a good mod to me now that I understand it.
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Yes, the rear edge of the oil grooves in the upper bearings are chamfered.