Back the timing down to 30-32 degress to be safe. Put a wide band on it and keep the AFR's in the 11.5 range. I would not go any leaner that 12 AFR.

Modern combustion chambers, and aluminum heads, you should not need that much timing.

11.5 is too rich, you will reduce power and not be any safer than 12.5 AFR. You should be able to cruise all day in midrange rpm at 12.8 progress towards 12.2-12.5 at WOT for NA SBC. No load idle run the AFR around 13.8.

I had my Diamond Pistons set at 0.022 and pinched the top ring when I had some detonation. Looked just like that. I have a SHP 4.125" x 3.875". Total timing set at 33* though peak power on the AFR 210s came in at 36*. Not sure what happened. I had Autolite 3924 plugs, I think I may have had a plug start to burn and cause havoc, or an injector started to go. Uping fuel and pulling timing did very little to curb the deto. It went away on its own and rear again a couple of weeks later and boom. Pistons are now set at 0.026"

Crooks,you are a step way above between 414 ci and procharged efi. But we can all learn from each other right?
I bet I am being saved by the Thunderbolt V knock control. My engine is 10.2:1 static and it runs theoretically to 34 max degrees timing. I have always fed it 93 octane.
Now you guys have me digging out my build notes to see what ring gaps I set in 2016.

I agree. Brain fart, guess I have been watching the wide band in my truck too much under boost.
The numbers I posted are around what I run on my turbo 383. Mid 12's for AFR at WOT are what you should see for NA.

Looks like I might have to start a new thread regarding widebands and O2 sensor location.

I see in your signature, that you run a procharger? Was that on this engine when the rings butted?

To the OP,

My engine is very close to your original build. 385 (.040 over x 3.75 stroke. 9.39:1 comp. .040 quench with ProMaxx 183 Maxx series heads. I am running the rpm air gap with a Lunati 219/227 @.050 roller cam w/ 112 LSA.. I also have ran a 600 edelbrock for the last (2) years but in a smaller and lighter boat. (21' 3200 lbs.) I can tell you if you haven't changed the needle and seats to the larger size and removed the inlet screens on the needles, there is no way you were getting enough fuel. With the larger needles, I can run wide open as long as I want with great fuel pressure. No matter what I did fuel pump, jets, needles, etc. I would drain the carb of fuel in about 15-20 seconds of wide open before. With the right needles I was also able to jet it back down (1) step above stock. Mine makes great power at 35 degrees timing. I just finally installed a Holley 780 vac secondary carb today. Hope to get it on the water Wednesday to see how AF numbers look and how it compares to the 600 edelbrock. Good luck with the new build.

Thank you for the info. I am very curious how the Holley 780 works for you. Please keep me posted!

Yes it was.
I run an M1SCB with intercooler, what would normally come with the 350mag setup. Motor dynoed 615hp with about 6.5 lbs boost. Ran out of injector to try smaller pulleys.