This is my first post on Hotrodders- so I should first say thanks to all the helpful info that Ive been able to gather from searching these past few months. Ive been doing a lot of reading since my father and I bought an inboard ski boat with a 454 in July. For those familiar, its a '79 Barefoot Nautique, which was the first year that Correct Craft made this barefoot-specific model. I realize this is a pretty unique application compared to most here, so I figured Id throw a few questions out there that I couldnt find answers to.
First of all, here's what I know. Most Barefoot Nautiques came with 330 hp 454's, which were typical marine longblocks with peanut port heads. These boats typically topped out around 48-49mph. We first suspected that this one had been previously worked on when some carb and ignition tuning produced a much stronger 56mph on the gps. We started pulling casting numbers and here's what we've got (from Mortec):
Block: 14015445, 454 2 or 4 bolt ’75 – 87
Intake: 3933163, fits 68-69 396 375 hp, 427 425 hp
heads: 6272990, 70-up...rect...OPEN...454 service replacement, used on some MKIV crate engines, 118cc chamber
The engine is running great, but we will be pulling it over the winter since we are doing some structural repairs to the boat. We're considering tinkering with the engine to some degree if there are easy ways to add hp. I do not know anything about the pistons (I assume the block has been apart at some point), is there any way to determine my CR without pulling the heads? I also dont know anything about the cam- though I plan to measure at least the lift before doing anything. I suspect that it may be a stock-ish cam (peak hp on the 330hp engine occurs at ~4400), for 2 reasons. 1) We did not pick up any extra speed when we changed props that gave us 300 extra RPM at wide open throttle (5200rpm vs. 4900rpm). 2)This is a reverse rotation motor, so the availability of reverse rotation BBC blanks is and was an area that no one seems to know much about- including the Correct Craft forum, which has a lot of reverse rotation knowledge.
Based on the boats performance, my guess is that the engine is putting out somewhere in the neighborhood of 400hp, right around 5000 RPM. We would like more, obviously, without any adverse affects- namely low end power. We get an instant 2500 RPM or so from a standstill now, and while the holeshot is OK, its not great. Without propping down, we'd like to at least keep what we've got. I know the rectangle port heads are likely to be called overkill for our application, but it does run strong once the boat gets on plane, so Im hesitant to change them (though if building from a stock 330hp engine in the future, Id probably pick 781's or 049's as are commonly suggested).
I am not sure if a stroker is in the cards, but if I can convince Dad, whats the optimal size we should consider going up to? Ideally, Id like to see a powerband of 2500-5500 or so with the 990 heads, with a max RPM of 5500 or so (we can play with the prop to dial this in). Reliability is also key. What should we be looking at for a compression ratio- ~9:1? We run 93 octane now and dont mind doing so. What about cam? How big can we go on 454ci and not harm the bottom end power? Comp tells me they do reverse rotation BBC cams, though Im not super confident in the info I was given.
We do a fair amount of barefooting (39-45mph), so we need useable power, but we also would love to have the bragging rights that a 60mph ski boat would afford! I think another 50hp would get us there. If it matters, we're running a Performance Distributors DUI (HEI) with 24 degrees of advance (initial is set to ~12 deg) and a 750cfm 4160/4150 marine carb with the choke horn milled off. It starts and idles great right now.
Thanks in advance for any input!