I don't have the means right now to have the engine dynoed, so I am wondering if it sounds like I'm making the power I should with the following engine specs. It's a Chevy 396 configured exactly like the numbers shown at the left in the picture below. Only real difference is I have pretty decent flowing logs versus the small tube header open exhaust setting I used on DD.
http://webpages.charter.net/jlbarnes/boat/xm278dyno.jpg
The pump is a Berk JC with a Berk A impeller. My usual boating conditions are mid 80's and high (70% - 90%) humidity, about 1700ft elevation. The pump is tight - rebuilt with HTP wear ring about 100gallons of gas ago... Right now I see 4300 - 4400rpms max, and I have confirmed this with a digital diagnostic tach against the one on the dash. Since this is a heavy V-hull boat I am seeing about 48 - 50mph GPS.
I had been trying to decide if cutting the impeller to a B would gain me anything. It would take me a bit further up the HP curve, but on the other hand I'm already starting down the torque curve... So, I've pretty much decided against that. I have been considering advancing the cam a bit (it's straight up right now) to see if that helps get me a little closer to the HP peak. I've played with less aggressive cams in DD, but didn't see much improvement in mid 4000 rpm range... They dropped the peak HP back a few rpm's, but also dropped the hp at 4400, too.
I have searched through a ton of old posts, and while I haven't found any 396's with max rpms versus impeller size listed, I have seen enough mild BBC's listed spinning Berk A's in the mid 4000 rpms range to figure mine doesn't have any major tuning issues... What are some of your opinions on what I could do to dial this thing in for the best power? Not expecting any huge gains in speed, but any small gain would be nice. I might have to borrow a set of old OT headers and slap them on to see what it pulls then. I have an enclosed engine bay, and definitely no budget for jacketted headers right now but it would be nice to see what potential they had...
Thanks,
Jason