How much power is he telling you it will make, and how much are you looking for? And, how long are you wanting the engine to last between rebuilds?

i would think you'd have 3k plus into the block and machinig and another 3,500 min into the heads. That's 6,500 just between those two. With the kind of power your your planning to build I wouldn't scrimp at all on the rotating assm. Some have great luck with scat cranks but I honestly would be scepticle in anything over 454/496. I know there's a ton of them out there running flawlessly but i would really consider rethinking the internals. It's kinda like purchasing one of those White engines you See on eBay for peanuts. Nothing against them or any other company selling cheap engines and may be perfectly fine for street with short spurtts but not balls out for several minutes at a time.

I recently got some numbers together for a couple 565/572's

Block and machinig/prep 3k
Rotating assm 5k
Heads complete. 4k
Intake, cam, carb, lifters 3k
Gaskets, pushrods, accs 1k
Oil pan-pump, valve covers. 2k

18k Each apprx.

Corners can be cut here and there so say nock off 2k but then add the other little things that add up. Some of the above numbers are rounded off but the general cost are there.

I will say I admire you wanting to build reliable NA power regardless how you get there.

What kind of power and what RPM? I don't know if I would go that big with the heads and camshaft with out headers on a NA engine. As far as 4-3/4 crank if you don't rev the nuts off of it might work ok. That's my 2cents.

And I don't think you will have a good ring pack with that stroke and a 6.7 rod.

He is claiming 1000hp. I'm looking for a minimal 850hp. My opinion there is no need to spin over 5800 RPM. By comments in this post, his numbers seem to be on the extreme end of the spectrum. Im tired of buying other people's boats with a motor on the way out. Im looking to build a reliable motor that will last in a boat I plan on keeping for a long time. I want to be on the conservative end and have parts that will live. I have a huge oil cooler, 2 oil filters, canton 14qt pan and accusump system. We plan on traveling the U.S. and do several poker runs this year. I have the components to support a motor for long run durations, now I need a motor that can do it.

My opinion, if you are wanting a "Reliable" fairly long lasting engine, would be build yourself a 540-565 engine with the 9.8 block(4.25x4.xxx bore), and put a roots/screw blower on it(8-71,10-71, sounds like budget minded so prob roots/carb?), with a mild hydraulic roller camshaft. Keyword, "mild'. Enjoy a valvetrain thats easy on parts, and go boating. With that combo, 850hp can be done with 5-6lbs of boost, idle well, and live a long life. You'd be good with a sportsman priced crank/rods, off the shelf stuff, and a basic set of aftermarket heads, standard wet sump oiling, basic valvetrain components, nothing exotic. Focus on good machine work, good assembly, and a good tune, and you'll be good to go. The GEN 3 stainless marine exhaust works best with forced induction. Just my opinion.

Im of the same mindset, keep stroke (piston speed) reasonable by keeping stroke in that 4.250/ 4.375 range, keep bore at 4.500 ( stiff cylinders that wont deform), and low boost it if needed to reach your hp goal

1000hp forget about that the 850hp can be done but I would still be worried being a NA motor and manifolds. What outdrives do you have?

For the OP, follow Eddie Youngs advice and stay at/under 4.5 stroke.

My suggestion is to look at the Chevy 572 - 620 HP and use them as a base engine. You can buy the long block for 12,500 and finish for not a lot of $.