From reading your past threads, I realize you're probably the guy who will find a way to make it work, but based off what Dmaxes have been put thru in the past, I just dont see how one (let alone two) can hold at that power level for that long a duration even when built with the best parts money can buy now. You're looking at a lot of cubic dollars on a lot of very expensive custom parts to give yourself even a chance to make it work.
We're just not there yet in terms of reliability at the very extremes of high perf. Hope your customer realizes that...
I've had a hard time keeping his expectations realistic. But he understands why you don't see any big HP diesel boats running 400ci. We started out at 800hp, and he was soon talking about 1200. Which I quickly explained is not an option, unless you plan to build 4 more for spares.
I pegged the stock rod LLY with nothing but set of cast Mahle pistons for about 15 minutes straight one day right after the rebuild. Seated the rings right now.. lol. Then added those 10 WOT 1-mile runs on biodiesel for Guinness. After that I felt comfortable they will hold upwards of 700hp with EGT's around 1600. But even that low power range keeps your ears and eyes pealed for anything out of the ordinary.
All the oiling, water, and charge cooling issues are pretty well sorted out by now. I'm still questioning that Banks intake capacity, love the design but compared to what I've ran before, it's small. Biggest concern remains the cranks. Jeremy has 2 Callies on order for me after my friend snapped his new LMM up around 700hp. He's since put Guy on a stroker build for his boat. So watch for more on that one.
My best odds approach to the cranks is internal balance the Callies and slap a heavy azz flywheel on them. That's the only other rotating mod my LLY had besides the pistons, and you could feel the difference. Do everything possible to dampen the vibrations out of them.
As for the big Cummins marine options, I inspected the internals of a rock solid 700hp marine version couple month back. They run Monotherm pistons for starters. I spoke with Fingers a bit about the options, or lack there of, and we feel the cast Mahle is still second best option for longevity right now. Just gonna oil the crap out of them...
-K