I am assuming he did use a gasket between the oil pump and the block. If not,
there is the problem.
But, more importantly, did you Plastigage the journals before assembly, or did
you just trust the machine shop?
Also, the relief valve should be lapped in place before assembly.
But first of all, the 68 came with an electronic oil pressure sending unit.
It is very common for those to go bad. Check the oil pressure with a
mechanical gauge before doing any teardown.
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