need help for gx390

[jugghead]

What is the best camshaft for my engine gx390 if i need more speed. Planning to buy 307 lift 260 duration.what does it mean 307rpm camshaft grind?by the way my engine is for boat racing. Direct drive..

 

[Joe-405]

Some cams are made for torque and some for higher rpm use. That one is rpm style

 

[jugghead]

So 307 lift is for rpm?how many lbs of valve should i buy?and im planning to buy billet flywheel arc 6603.is it compatible with my cam?

 

[Joe-405]

The best way for that is to call the company that has that cam and see what they recommend. I've noticed that different companies recommend different combinations to work best for their stuff

 

[Cuda54]

Jugghead you guys really get those little boats flying on the water! They are fun to watch! Some of them really are screaming and sound like they are really high into the RPMs. What pitch prop are you running on your boat? That could make a big difference on top end speed.

 

[jugghead]

Jugghead you guys really get those little boats flying on the water! They are fun to watch! Some of them really are screaming and sound like they are really high into the RPMs. What pitch prop are you running on your boat? That could make a big difference on top end speed.

Ohh i see i only measured the diameter of the prop which is 8 inches..do you have any idea what prop is good for racing?

 

[neo71665]

Ohh i see i only measured the diameter of the prop which is 8 inches..do you have any idea what prop is good for racing?

Selecting the Right Propeller - BoatTECH - BoatUS

 

[Cuda54]

Can you get a 9" prop and try it to see it is any better? Most of the 8" props I have seen are a 8"x4 pitch so you would need to try a 9" to get a bit more out of it. You want to prop it to where the you get the max RPMs that your engine is turning. And still get the high RPMs with out bogging the engine out. So try to bog it a little then back down on the prop size to get the max RPMs. You might have to try a few to see what is best for your engine setup. I hope you do good!