Hal,
I agree with Scott that the most likely problem is worn rings and/or worn
cylinder walls. Another possibility that comes to mind is a clogged oil
gallery in the head or in the block. If the head is not draining oil back
into the block sufficiently, 15-20 minutes might be enough time to pump the
valve cover full of oil, where it begins to be ingested in the carburetors.
This story was recently told by many big Healey owners on the big list.
Although you don't want this to be true of a head you just spent a lot of
money on, it seems possible that cleaning the head dislodged particles that
blocked an oil gallery or that in the process of removing and reinstalling
the head, sludge/old gasket material got knocked into an oil gallery in the
block. Perhaps you could test for this by opening the cap in the valve
cover or by checking the oil level when the problem manifests itself?
While I don't doubt your mechanic's advice on the best grade of oil to use,
I have trouble believing this will be the solution to your problem. If your
car can't maintain sufficient oil pressure with 10W-30, it won't be long
till it can't maintain pressure with 10W-40, either.
Kevin Riggs
'72 TR6
rkriggs@ingr.com
Huntsville, AL
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