I've built and own a number of Twelves and Su8s over the years. Fortunately, none had cracks, even some nasty rusted junkyard blocks. Never did any 1938s, though. David

Those kind of hacks are criminal in my mind. The average shop shies away from antique repairs and the car owner takes his chances elsewhere often getting bit as in your case. Seen this many times thru the yrs, mostly w/ engines. These are the reasons many don't get an antique car and hurts the hobby. I believe word of mouth usually is pretty reliable if you consider the source.You've documented much. Does the owner have any recourse?

Adding to Tim Coles excellent reply,
I've found excessive clearance in the lifter guides also adds to that noise. I make my own. The clearance in them depends on if you want to drive 45MPH or 100 MPH. The complication of Packard's valve train was to limit valve guide side loading. Today's alloys and cam profiles can eliminate that. There's a lot of parts in that valve train. It's rare to hear a quiet one.David

Your response could write volumes. Probably purchase an available reprint on the subject. I can tell you all the Std and Su8 '30s engs have 9 mains. Those two series have different cranks and bearings thru the yrs. Plus the brg clearance varies w/ the brg alloy. Do you have a specific plan w/ one of these engs? Or just curious?
David

Reply to post 26,
All eng configurations have a different procedure. I'm assuming you're talking a 90 deg V8. That eng crank is not balanced separately. Actually no crank is ever balanced on knife edges. That is the wackiest idea that's ever been floated. A separate story.
A V8 is extremely sensitive to changes in rod or piston asmy wt. A (bob) weight is clamped on each V8 journal to represent a % of the component's wt. The oil in the crank's rod jrnl is also factored. A natural resonance peak is read on the crank w/ the bob wts attached, then spun. Each end of the crank will have a different plane of imbalance. It might look fine on knife edges but create thousands of lbs of imbalance force when running. The corrections are made on the counterwts. Sometimes removing wt if new parts are lighter or Mallory if they're heavier. Hope this is helpful. I'll answer about externally bal'd engs another time. David

Custom Clipper . Yes, Sometimes Heavy metal(almost pure tungsten) is added. It's installed axially w/ press fit , no weld needed or wanted. I hate to say the tens of thou tied up in stock.

replying to post #23. Mr V8. I'm sorry to say that everything you say has been absolutely wrong in all your posts on this subject. It's obvious you don't have the slightest clue.It's a real disservice to the members here to feed all your wild off the wall statements. I'd be happy to explain with facts if you're interested. I don't enjoy turmoil or upsetting anyone but there are some here that would like the truth. David

Poor eyesight, too. I meant post #21. Long day. I start at 2:00 AM. David

I'm sorry to say that post #22 didn't have any engineering background, just conjecture, plus thinking the Packard Factory was good in their design and manufacture of engines is a MYTH. They were terrible. I've been redesigning and remedying their design problems for many years. I received a PM today which I'm not bright enough to understand. Someone in Elkhart,IN that restores aircraft. I've been advising those people for yrs. Often tell the FAA they couldn't fix a bicycle. It baffles me that guys don't want to learn. A&P guys scare the H out of me w/ their lack of knowledge but they dive right in because they have their ticket and it doesn't matter to them if the craft goes in. Deal w/ it all the time. I've not said anything of my background and can't understand why the possibility of helpful advice is threatening to some. Is this Site a closed society? Went professional in '52 and have kept diligently studying ever since. Ought to take what I have to offer before I'm gone, kids. Cancer is not fun. David

Mr home away from home,
As a matter of fact blocks and caps are routinely linebored first and then the inserts line bored second. It was the only way engs of the past were done and are still today. I realize I'm new here but it certainly appears any REALLY professional help I'd like to share here is intruding on YOUR site. Sorry, I'll leave. David