Not probable issue. If the new rings seat well or not it would not cause this. Although too small of a ring gap might. Your machinist would not make an error here.

The real issue here is the actual cause may or may never be identified. Worth investigating as far as possible though.

You and your machinist have a long standing relationship. So really consider any question before asking him. I would not accidentally insult him. For example did he plastigauge the bearings to crank fit or just go by the numbers on the bearing boxes.

You can quietly do this yourself to check that there was proper clearance on any bearing that still looks normal. I would do one rod and one main bearing. May as well get this possible mechanical aspect out of the way first.

Bearing replacement size was known and if the crank shop did not get things quite right. Or the bearings if ordered later. I still think your friend would have double checked but you cannot be absolutely sure. We all can mess up sometimes. Something caused this event. It is best to start with the basics.

I even wonder if the dyno people put too much of a load on the engine during testing. There are limits to almost everything.

I don't understand this new flangled oil.Back in my day,if you raced you used w40 racing oil, by penz.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

There are so many options it is pretty hard to decide what to run. I am afraid to go very far from the factory original specs because the cam advance mechanisms are activated by oil pressure and I don't want to alter how they work.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I see the carmakers going to multiweight oils only to make them get better fuel mileage. but not for protection cause you make more money when people keep buying new ones.Notice
alot of new engines you can't rebuild,like telling a machinist you harden cylinders with freezing,thats bull. You harden steel with extreme heat treat.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

Yeah, but if you put heavy oil in a car designed for lighter oil bad things happen, like lifters tapping etc.

I put 15w40 in my 84 500SEC and it made a valve lifter tap. Drained it out and put in full synthetic 10w30 or 40 and it went away instantly.

You gotta run what they are set up for, or close to it.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.