https://cimg4.ibsrv.net/gimg/www.off...7bbc3aa46.jpeg

Do those AFR's look a tad lean for boat engine?

Pretty good numbers

I am assembling a Gen6 454 with a slightly smaller Hardin roller cam and ProMaxx 290 heads and an 800 Holley. Which jets did you use and do you think more fuel on top would have helped, or did your dyno guy think the AFR was good?
You have plenty of cam, I would have expected the peak HP to be higher than 5300 thats why I ask about the AFR

Just love this article I have based most of my build on it for my 22 Donzi. Thanks for the writeup

What often causes the nose over of the HP curve is the peak intake flow vs time. Something chokes off the air getting into the cyls.

Maintaining a long shallow peak curve comes from sufficient exhaust duration/flow to reduce the evacuation pumping losses.

In this case...with good flowing heads and 236° cam, the peak HP is low at 5300. (For the CID of course)

Maybe it was the carb he ended up using on the dyno was not setup well. Maybe a correction factor error? But that wouldn't affect HP/RPM curve.

Important to note...the BSFC numbers are often calc'd to the actual HP made vs fuel conumed...not the 'corrected' HP numbers.

My 509cid with The same 4" stroke, 290cc flotek ovals, 240 @050" intake duration, Peak HP above 6000rpm

That pull was with a Willys carb that Ray just pulled off his car. The carb I brought was the original one that was on the engine. It was a Holley but we couldn't tell whether it was a 750 or 850. It had not been gone through and I don't know what jets are in it but it needed to be rebuilt as it had awful idle. With that set up the AF was 12.5 everywhere and the plugs looked good. We didn't really have time to get into the jetting. The base timing was just 8 and advance was just less than 30.
I'm having a custom carb built and will bump up the timing. On one of the pulls I have a photo of 573HP at 5300. I don't know if this set up really should make much more or not. It is interesting though that it was done at just over 5,000. Could be the dual plane intake.. But I'm in this build for the long haul. I want it to be dependable and last and won't drive the fire out of it. All the low end torque ought to make it fun.

slight correction, speaking of :)
bsfc is always calculated off of measured hp and fuel flow. Never off of corrected hp.

Yeah, with an 800 carb built properly and 32 degrees timing it will be a great engine. Please share the results I would like to see the before and after numbers in your Superboat, which isnt that different from my Donzi
With that cam it wont idle well at 8 degrees. 12-16 is better starting point I think with 32 total. And since it may have ran out of fuel on top, plus not enough time, that would explain the drop off at 5300.

I will be tuning in the boat, so no dyno other than the speedometer, starting at 32 degrees and going from there.

I want to get a good 5 years out of this engine and will start working on a 540 at some point