I measured intake vacuum at 15" but given the overlap in the cam I am not sure the low reading is an indication of a problem. The engine was cold and idle was not smooth so I probably need to retest it to be sure of the reading. My vacuum gage is older and seemed stable but I didn't check it for an orifice.
The block is a 1991 Chevy 350 that was machined oversize and honed by a machine shop that has a good reputation.
Consensus seems to be that at this point the rings are not going to seal any better so I will probably run it a bit more before scheduling a time to pull the engine and tear it down.
In the past I have always used standard (not synthetic) oil and not had a break-in problem but this time I struggled to find an oil that was not a synthetic blend (probably didn't look hard enough). Engine oils are constantly changing formulations and seem to be trying to get longer and longer service intervals which is great except for break-in.
