This is Main Bearing #2. It was assembled with .002 - .0025 of main bearing clearance so I assume the Cast Nodular Iron crank flexed and scuffed the bearing. Will have to assemble with .003 - .0035 of clearance next time to prevent crank flex from damaging bearing surface. Will also have it checked for straightness

 

I'm wondering if "over-revving" could cause the old TRW piston rings to "flutter" and get hung up and break, therefore breaking the piston ring lands?? Engine spun to 6,200 at times with heavy TRW's, factory rods and cast nodular iron crank.

The tops of the pistons were completely fine, no signs of detonation.

 

Those big fat rings aren’t the most stable so no telling what’s going on there.
If you’re looking for longevity insurance, align hone it and have it internally balanced. I’ll bet you won’t have anymore issues as long as your tune is correct.

 

I used the Wiseco Pro Tru on my 455 and was really happy. I wanted a quality piston and my machine shop had the most experience with the Wiseco is the reason I used them over the others. I was only a 427 HP engine with stock manifolds so not sure they would be right for your build but just another option

 

I've heard some say 36 degrees of timing with iron heads and 10.1 compression is OK while others claim only 28-32 degrees of timing is acceptable with iron heads and 10.1 compression. With 91 octane gas.

 

No more than 34* when running 91 octane. And that’s with a good tune.

 

What’s oval honing??

 

For one of these, Sorry, I couldn't resist. I am not sure what it is either

 

When I refer to oval honing its the connecting rods I oval hone.

 

Dick Miller claims the factory "CN" is stronger than the "N" crank. Not sure if this is provable but somehow the "CN" version is stronger than the "N" version.

 

Other engine builders have said that they thought that the CN crank was the best of the cast Oldsmobile cranks.