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350 magnum questions

Old 09-02-2021, 12:49 PM
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Default 350 magnum questions

Hey everyone I'm looking for some advice on parts id like to install on my new boat. 1989 Ebbtide Campoine 204 with a 350 Magnum. Right now I can run about 53mph with my buddy in the boat with me and a full tank (3 blade aluminum prop 22p if I remember correctly). My holeshot isn't very great though. I have a lot of experience with engines but not much with boat specific engines and their needs. Looking for some more low end power and torque. I have a few questions so I'll list them along with the parts I'm thinking of buying.

1.) I'm looking to get a set of Vortec heads (with valves already installed) and am wondering if my current intake and exhaust will fit. The engine seems to have a high rise intake. Not sure if that's stock or not.

2.) If my current intake will not fit on the Vortec heads then what intake would you all suggest on the cheaper side?

3.) I plan on getting a Holley Carb. Would 600CFM suffice with this set up?

4.) I plan on doing a cam down the road, hopefully during all this maintenance if my wallet allows. What cam should I look into getting?

The heads I want to get are on 2040-parts P/N 12558060.
I'm not able to send the link just yet.


Thanks in advance,
Cameron

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Old 09-02-2021, 04:32 PM
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Vortec heads have a different intake manifold to head bolt pattern and angle. Vortec heads also have a raised intake runner vs earlier versions. This means youll need an intake manifold made for Vortec heads.
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Old 09-02-2021, 04:35 PM
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Aluminum props dont offer great oerformance because of material (alum flexes) and design.

Your top rpm at wot and best soeed trim position should be 4600-4800rpm. Where is it now ? Is your alpha gear ratio 1.47 (1.50) ?

Most small boats with 350 mag carb use 19-21 pitch props. 19 more than 21.
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Old 09-05-2021, 10:38 PM
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I believe my WOT rpm was 4800. Im swapping a stainless prop on tomorrow. Any idea what intake I should pickup for the vortec heads?
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Old 09-19-2021, 06:15 AM
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You'll do best with a dual plane intake. Mine has a dual plane air gap. Which allows a cooler fuel charge since the carburetor mount point is not in contact with the engine. When you look at these make sure there is over head clearance in your engine compartment for the intake, carburetor and flame arrestor. The parts all can be checked for height in the sellers info.
The vortec heads have a lift limit out of the box. If you are contemplating cams you'd best cut the valve guides on factory vortec heads so you don't have to remove them for the cam later. This issue is so well known that there are kits so you can lower the guides yourself. And obviously, machinists do it too. Or get some aftermarket vortec style heads that already have the shorter guides.

Last edited by NHGuy; 09-19-2021 at 06:19 AM.
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Old 09-19-2021, 03:12 PM
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Here's good advice. Save your money. Vortech heads will give you 20/40 more HP and already you have $800 in them. Then machine work for a larger cam (stock heads are set up for about a .420 lift and the install of threaded rocker arm bolts instead of pressed in. Cost of a cam and springs. Cost of a manifold and carb. Labor. Price of a stainless prop which has down sides.

And for what? A few more MPH? Your boat is what it is. It does 53 already. Be happy with that.
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Old 09-19-2021, 04:46 PM
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This used to be a perfornance boat site AmiableDave, what happened ?
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94sylvan (09-23-2021)
Old 09-19-2021, 05:58 PM
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Originally Posted by SB View Post
This used to be a performance boat site AmiableDave, what happened ?
I don't get your meaning...........
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Old 09-19-2021, 09:09 PM
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Originally Posted by AmiableDave View Post
I don't get your meaning...........
we're performance boaters,,we have the need,the need for speed.
vortec heads,tunnel ram,2 700cfm carbs,,3/4 race cam and a 1000hp shot of nos,,lets get that boat moving.
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94sylvan (09-23-2021)
Old 09-19-2021, 09:46 PM
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You need good heads, a 383 kit, a belt driven intake manifold, then the alpha becomes a weak link so your going to need a bravo setup. Googling your boat, most were egg beaters, so your drive is deep, so ad a 2" shorty to the bravo.

that should have you in the upper 70s......

In the mean time, if you start holeshoting an alpha with an oversized stainless prop, buy stock in SEI.

Blueprint has a marine 383 carb to pan for 7k

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