Heads?

[Nordic79]

Have a 460 chevy with 871 BDS
blower and twin 850s.Am looking to
going to Aluminum heads and roller
cam.There are many heads out there
and all are good to a point.Should
be running in the 3500-7000rpm
range on the engine.Any of you
Blown guys have a suggestion n
which heads would work the beast
with this combo?It is a jet with B
impeller.
You can take a look at my boat on my homepage in my profile.
[This message has been edited by Nordic79 (edited September 03, 2000).]

[dropkeel]

Nice boat! http://free.***boat.net/ubb/smile.gif You should be bumping 100mph with what you have though.Do you have a shoed intake? What degree is the intake set in at?
I recommend more boost with the Merlin 345 Iron heads and get that bottom up to snuff! http://free.***boat.net/ubb/smile.gif

[Nordic79]

Thanks Dropkeel
Everything is not just where it should be yet.The boats seems to be getting air when at WOT.Not sure if its getting to much or not enough water to cause this.Can not hold the throttle all the way open because of this rpm surge.Not sure what loader is in the boat or where it is set at.Do need help in this area. http://free.***boat.net/ubb/frown.gif
This motor has been in the boat for 20 yrs and not been down!!Does have room for improvement.

[HighRoller]

I think the intake is most of your problem,like dropkeel said you need to investigate a more aggressive intake situation to keep the pump loaded.I also would recommend you check into an impeller system where the primary impeller is loaded by an additional smaller impeller near the intake(i.e.American Turbine's"Inducer")This system seems to work good for high horsepower applications.

[Nordic79]

Thanks Highroller.I do have the inducer in my pump.It is all new setup!Has a B impeller.Really not sure if this item helped or not.

[HighRoller]

I also forgot to suggest asking some people their opinion on going to a steeper impeller(A or AA)it might bring the rpm down into the meat of the powerband for your motor.I'm assuming since it's a blower motor you don't turn it a million rpm.I another option(depending on the boat's weight)would be a nozzle sleeve to adjust the orifice size.

[spectras only]

nordic79, wen you have lots of HP you can reduce the nozzle size but I feel you have too much clearance between impeller and wear ring.You said it wasn't touched for 20 years, I would pull the unit out and install shoulder wear ring and go up to a AA.You loose approx 400-500RPM and maybe 3MPHon top end but would fix the cavitation problem.