Originally Posted by Guy Hiltz
With those heads you may want to shoot for 6500 rpm to meet your goal.I dont know anything about reverse rotation cams,but you could call UDHarold Brookshire for a custon grind,662-562-4933,or 662-301-1245.You may also want to consider going with a solid roller cam.There are better intake manifolds available,the one you have is decent,but its an old design from the 60's.A Weiand Stealth would be a better choice.Your carb is a bit on the small side,an 800 might be better suited,and your timing is too low,big blocks like to have 36-38 degrees BTDC total timing in by 3-3500 rpm.If I were you,I would work on this combo before going stroker.
Guy, thanks for the response!
I realize the rectangle port heads like lots of RPMs to make power, but Im very leary of running 6500 on this application. Thats a ton of RPM's for a ski boat thats always under heavy load (unlike a car). We'd be pushing 5k RPM's at barefooting speeds with a prop that allowed us to turn that much at WOT, which we hold for minutes at a time. Reliability is a major concern! The factory HO 454's from the late 70's through the mid 80's were rated between 390 and 425 hp and were propped the same as the 330hp motors- they just spun more RPM's (5500 vs. 4400), hence my desire to keep RPM's in the mid-5k range. This is why I mentioned stroker- a few more cubes would help me take better advantage of my existing heads while keeping the RPM's down, right? Ive built engines before, but Im still a BBC newbie.
Ill give Harold a call and see what he can tell me- thanks for the reference! Ive been looking for a BBC cam expert, I dont have a lot of faith in the techs at Comp when it comes to this oddball application. (Ive found Cam Research to be a great resource for my Ford boats.) From what I understand though, a roller cam is going to be big bucks- apparently those blanks would need to be custom made and run $2k+, which isnt in the cards. Id just like to stick with a warmed up hydraulic flat tappet that can make better use of my top end flow without killing my bottom end power... hopefully theres a happy medium here.
As far as the Stealth goes, I assume you mean something like the 8018 (dual plane, rectangle ports)? Ive got one of these on a 351w and absolutely love it. Any idea how the height compares to the vintage piece Ive got? Ive got workarounds if there are motorbox clearance issues- just curious.
As far as timing goes, Ive got 24 degrees of advance built into the DUI, so with 12 initial, we're seeing about 36 total and its all in by 3000 RPM's. The ignition upgrade really woke up the holeshot of the boat, so it was a huge upgrade from the antique Mallory that was on there before.
The factory carb on the 330hp 454 was a 650cfm Holley. For whatever reason, marine engines seem to run pretty well with the smaller carbs- my 302's run 450cfm, my 351w a 600cfm. I figure unless I want to run this 454 past 6500rpm (which would require 768cfm at 90% VE) or stroke it to 496 and run it past 5800rpm (which requires 750cfm at 90% VE) then what Ive got should work, right? Or are BBC's notorious for running better with huge carbs?