Help from Engine Techs

[Daniel Wolfe]

I have a 1993 Advantage 20.5 Open Bow Classic. We still love this boat but I would like to make some changes. I would like to put in a roller cam kit, change to some aluminum heads and switch to the single plane intake. I was looking at some Dart pro 1 heads. Any idea what size intake would I want? I was thinking 315 or 325 or should I go 335. I was thinking Competition Cams roller cam and roller lifters kit for a Jet boat with a power range 2000 to 5500 with some roller rockers. I know it won’t be a lot faster. Just looking for some changes without sacrificing reliability. Does this sound like some feasible options? Next is pump blue printing and new interior now that kids are older.

 

[28Eliminator]

Those heads are too big. Stick to a 305cc runner or smaller. Dart makes a 275 or 285 I believe. Too big a runner and it will be a dog.


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[Daniel Wolfe]

Thanks for the information. That’s what I needed.

 

[28Eliminator]

Thanks for the information. That’s what I needed.

Mine is 516”, and I’m running 305cc AFR heads. Strong carb signal, and made close to 600hp.

Good luck with your project!!


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[obnoxious001]

Those heads are too big. Stick to a 305cc runner or smaller. Dart makes a 275 or 285 I believe. Too big a runner and it will be a dog.

Basically good advice, but I put together a 489 in a 20' Schiada jet for a guy with larger runner heads that is not giving up anything on the bottom end, I broke it in and tested on the river. It's a matter of matching components properly.

 

[Daniel Wolfe]

Thanks guys. I believe it’s a dart pro 1 intake manifold. I’ll run my 850 demon and MSD Ignition. The exhaust is indmar but would like to change that in the future. I want to keep the dog house even with the new interior so I’m limited on clearance.

 

[28Eliminator]

Basically good advice, but I put together a 489 in a 20' Schiada jet for a guy with larger runner heads that is not giving up anything on the bottom end, I broke it in and tested on the river. It's a matter of matching components properly.

Well, you certainly know a lot more about it than I do [emoji106]. But do you agree that bigger is not necessarily better with an N/A carbed deal? Port velocity = cylinder filling, better PV with a properly sized runner?

What sizes runners did you run on the 489?


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