You could also have a lean spot at part throttle causing some unnoticed detonation.
Just food for thought Tim.

I've seen where too rich can trap fuel between the rings and igniting there damaging the ring lands. Now introduce some oil into the chamber , and oil will promote detonation

I just read this you posted; you stated the engine builder sucked. You redid the heads and something on the by-pass along with shimming the oil pump for more pressure. It just seems to me, maybe you should have taken these engines to your buddy and let him at that time, tear them down and correct the build before wasting an engine. I was just trying to understand how this being said; leads to cheap parts or a broken rod bolt as cause of failure at the beginning of this thread.
It's like blaming the cam; if the engine isn't making the power. Thats a little joke; Madara, and myself have between us.

That's exactly how I do it, wot shut off, another addition I wanted to add this winter is widebands, but didn't get that far, listen I get that there are 10 different things that might have happened and 25 different opinions, I don't have endless budget for 20,000 each engines, efi and all that for a old 35 cig, I do the best ican with what I can afford, I do not use credit for boating it's all cash so there are limits for me I refuse to go in huge debt over boating. I don't know it all, by far am not clueless either, I listen and take all advice given and may guess wrong and may guess right at times, this is not needing to get into pissimg match.

Could it have detonated? Sure I guess so, has it ever been close before? No so my first addiction is not detonation, I will pull plugs and see if something looks close to melted at all... When it's torn down we will know for sure...

Would I like to hand my engines over and put too of line parts and pay someone to build them? Yes buy I can't... So if it breaks sonetines it breaks, again I did not build these engines and I think after this the outcome will be
Much better, had issues when I learned my 454's and had oiling issues, listened to my buddy about what to do, I beat the fuk out of those engines every year for 5 seasons with not one issue, yes not as much power but let's face it 600's are notjing crazy these days either.... I don't know it all and won't tell you I do, but I will reply with what I do know and see..

So far from this thread I get the scat or pbm stuff will suffice for my application and should upgrade rod bolts to 2000 series, and that I will do

I didn't want to be down all summer took a chance and you see result, simple as that, I did what I knew would for sure destroy them and 55 psi of oil pressure, 260+ oil temps and non inconel valves were the biggest concern, am I wrong?

True, and as far as people around me for advice, you know Bill and if you know him well you know he's a very smart person to get advice from also... I was talking to him yesterday

Bottom line at this point lots of things could have caused it, bottom line everything within my financial power and brains around me will be addressed for the future...

Absolutely. Between, Ray, billy and Scott, you will get good counsel.
I'm sure it will all work out.

Thank you, at least I get a little credit for not being dumb lol the best ford engine I ever built was designed by Bill and Jeff Chambers...

I wired Jeff's dyno shop. Lol.
He tuned my 347 last year.