Grant 302
basic and well known psychic
I wanted coated bearings and min. is .0011" so I'm still to the tight side of the ledger.
And there's nothing wrong with that. I wouldn't call it tight for these engines. Spec is 0.0010" to 0.0020". For the OP's use, and to survive his next enduro, I would choose to run the tightest cold clearance possible. Aluminum expands a lot even at 200º F. Reportedly about 0.0005" at the mains. Race temps likely push that up to (my estimate) of 0.0007" at 250º F. And I think that's conservative.
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One more reason why I suggest to cool the oil and use the piston squirters when possible.