I was wondering what rpm all you BBF guys are running at WOT... I am gonna be rebuilding my 460 Ford over the winter, and my engine builder is telling me it will cost a fortune to get the motor to tach over 6500rpm reliably... Main problem is its going in a jetboat, so i need it to tach 6500 to get any real speed out of the boat...
What kind of RPM numbers (and speeds) are some other fellow BBF jetboaters getting? I am looking for 80-85mph, and i am prepared to spend 6000-10000 on the motor (including new headers)... any help would be great.
Actually, you don't need to be over 6000 rpm. If you create high enough HP #'s, you can turn an "AA" impeller and move more water than the "A" you are probably turning now. You can put a 10000rpm engine in it, but if doesn't have the HP and TQ to move water, you won't be able to do jack. The HP and torque numbers are more beneficial than the overall RPM #'s.
I agree. You want to match your impellar to the peak HP and you want enough torque to get you there. All of us over at Banderlog.com has hashed the hell out of this topic. But that is the conclusion I have come to.
It shouldn't cost anymore to build a BBF to spin a decent amount of rpms than a BBC. You'll need top quality valve train, a good set of rods, forged pistons and some addional bearing clearance. I've heard some truck pullers turning the BBF 84-8500 rpms so I suppose you shouldn't have any trouble turning 6500. Personally I have turned 460s and 514s 7500rpm with just the usual stuff.
I have turned a bbf to 5600 rpm on nitrous.all internals STOCK.ran well and still is.about 1.5 years since rebuild.
They're strong motors, snorider. Generallly, I agree with the others that you won't need the super high rpm's to get the power you want.
I'd like to add one more thing: It sounds like you will be building a motor greater than 550HP. Several BBF engine builders I have spoken with mutually agree that the stock main caps suffer cap walking above 550 HP(dyno testing). I don't know how much power you want to get out of your motor, but in the interest of longevity, I recommend doweling the mains while you're in there.
LO
You could put a $10,000.00 ford in a bayliner and it might still not reach 85 mph.
What kind of hull are you going to put this in. This is where you want to start making it right.
As far as rpm, I would build w/ some type of forced induction and keep the rpm abound 6/6400 rpm. You can build the bottom end super strong, put aluminum heads (for detonation issues) on w/ some HD exhaust valves. You won't need a real big cam so you wont have the rpm reliability issue.
Just some thoughts on which way to go smile_sp .
MikeF:
What kind of hull are you going to put this in. This is where you want to start making it right.
Bayliner - pah... And at 85mph in a bayliner, you could probably watch the fiberglass open up like a soup can... *cough* quality bayliner construction *cough*
The hull is a 1978 Sleekcraft Kauai 19' Jet.
Some pictures: (Click to enlarge, its magic)
And since after seeing this, someone is gonna say "You need a diverter, droop, etc"... Already chatting with Duane at HTP about those goodies
[ May 27, 2003, 10:22 PM: Message edited by: Snorider ]
Well, lets see, I have a 60 over 460, stock crank, rods, d3ve's, comp flat tappet cam, with 3% under bout 5/6 psi I am turning bout 5000 rpm at roughly 72/74 mph, little down from last year as I have lowered the boost. Why do you need 6500??
Blown 472:
Well, lets see, I have a 60 over 460, stock crank, rods, d3ve's, comp flat tappet cam, with 3% under bout 5/6 psi I am turning bout 5000 rpm at roughly 72/74 mph, little down from last year as I have lowered the boost. Why do you need 6500?? I guess i dont need 6500 - actually i really dont know what i need. In an attempt to keep costs low i will probably stop at around 6200rpm -which should be plenty.
Right now i have an A impeller probably turning it at around 4800rpm, and doing 60mph. That is why i assumed i need 6500rpm... but 6000 would probably be plenty of rev's to stretch some parts
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