This looks like an interesting new engine the sb4 developed my mercury racing and the roadster shop. It’s ls7 based with dohc added article claims 750 horsepower and Reving to 8000rpm. That small block rpm sort of makes me think of the original z28 302 engines.
Only $33,000 not including options, so you won't see it at the Challenge anytime soon. 
Still, it's pretty cool. http://roadstershop.com/engines/mercury-racing-sb4-dohc/
Mast Motorsports builds 9000rpm, 900hp LS7s that are still natutrally-aspirated and pushrod actuated. Likely cheaper and less complicated as well.
How long are the valvetrain components lasting on an LS that revs to 9k and makes 900hp? What are the valvespring pressures like?
NickD said:Mast Motorsports builds 9000rpm, 900hp LS7s that are still natutrally-aspirated and pushrod actuated. Likely cheaper and less complicated as well.
Having worked for Mercury in the past, I'll take the Mercury engine everyday of the week and twice on Sunday.
I feel like the Mercury engine, being for a boat, is designed to run flat out for hours. The Mast engine designed for short bursts of WOT.
Marine applications have to be really tough to survive. Not only being able to run wide open for hours, but with hugely variable loads on the drive train.
Offshore boats are frequently airborne, then slam down and load up the props again. Typically have a throttle man whose main job is to keep from over revving when the props catch air.
The driver just steers.
A lot of those really high output marine engines are only expected to last a few hundred hours between overhauls when run flat out all the time, however. Some of the highest output Mercury Racing stuff specs overhauls at 100 hours, IIRC.
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