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355Rookie 11-18-2012 05:26 PM

Help
 
I have a stock 355 that I want to put on my airboat but I don't know what cam and intake or heads to run in this motor to make hp and tq i need

355Rookie 11-18-2012 05:28 PM

I would like to make around 300hp

vinniekq2 11-18-2012 05:41 PM

what is the p.s.r.u.ratio? what is the prop designed to do, is in a constant speed prop?

355Rookie 11-18-2012 05:50 PM

I run a three blade prop and it is made to handle 400hp

355Rookie 11-18-2012 05:52 PM

And what is p.s.r.u

355Rookie 11-18-2012 05:58 PM

The prop can only spin up to 3200rpm
So that's what I need help in making as much hp by the time I'm at 3200rpm

vinniekq2 11-18-2012 06:06 PM

Propeller speed reduction unit, basically a transmission gear reduction with no neutral or reverse. 3:2 is common.
A propeller is designed to convert rpm to air flow with the pitch determining how much air and what horse power required to turn that rpm.This information should come with the prop.A constant speed prop changes pitch to keep the RPMs constant even when throttle position is changed.
If your prop is fixed (not adjustable) you will need a governor and or rev limiter is required.
If the prop is over driven the tips will go super sonic which can cause the prop to come apart,or just be so noisey you cant stand the sound.

hcompton 11-18-2012 06:12 PM

Didnt most air boat guys switch over to lower power vw style engines or aircraft style engine for higher power apps. I thought the days of chevy powered boats was done. Or im i just nuts?

355Rookie 11-18-2012 06:18 PM

Your nuts I don't run a gear box or none of that its a direct drive
And I can pitch the prop to what I need for what I need to do with the boat

355Rookie 11-18-2012 06:32 PM

The Super Snapper™ blades are a 10" wide blade that offers superior durability with its nickel leading edge and aerospace materials. This propeller has been designed to operate in RPM ranges from 2700 up to a maximum of 3000, with horsepower ranging from 125 up to 400.

vinniekq2 11-18-2012 06:33 PM

variable pitch that is adjusted without the engine running is better than fixed.Im not nuts,I was tested(big bang theory)hcompton is correct a boxer style lycoming or continental from a GPU is best.The chevy needs to be isolated from the prop because of thrust loads. Use a stroker if you use a chevy power unit. 396 small blockor 434 small block will make 300 H.P. at 3,000 rpm easy.If you use a 350,also use a psru with 3:2 ratio and it will work great

355Rookie 11-18-2012 06:40 PM

Ok say I was going to put this 355 in a car and I want it to make 300+ what would you use to get that

vinniekq2 11-18-2012 08:44 PM

300 horse power 350,I would use a 4 barrel carb,aluminum intake,headers,mild cam 430 lift 215 duration at 50,9:1 CR with cast iron heads.should make 300 plus horse power at 4500 to 5000 rpm


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