Cam selection for a small block 5.7 chevy?
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Cam selection for a small block 5.7 chevy?

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    Member Dano214's Avatar
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    Default Cam selection for a small block 5.7 chevy?

    Im thinking of upgrading the cam in my boat. So what I have know is a heavy ass boat with through prop or drive exhaust and i have no clue what would be a good all around cam. I want to boost the performance of the boat, its currently a stock 5.7 but im putting a edelbrock performer intake and carb on it. I know if i go to big on the duration it will suck in water, also the heads are stock so i know i don't want to go a large lift but what can i throw in there to add performance? Any advice or thoughts?

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    Quote Originally Posted by Dano214 View Post
    Im thinking of upgrading the cam in my boat. So what I have know is a heavy ass boat with through prop or drive exhaust and i have no clue what would be a good all around cam. I want to boost the performance of the boat, its currently a stock 5.7 but im putting a edelbrock performer intake and carb on it. I know if i go to big on the duration it will suck in water, also the heads are stock so i know i don't want to go a large lift but what can i throw in there to add performance? Any advice or thoughts?
    These guys are going to want a bit more info on your setup . pics would help too

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    New here Beer:30's Avatar
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    I would pick one of the "Xtreme Marine" cams. However, you won't realize any changes in performance until you get the exhaust reconfigured. You would pick up 20-30hp just by ditching the through-prop. You probably wouldn't need any other upgrades after that, if that's all the perf you are looking to gain. You would also need to know if you have a Vortec motor or not. If it's a roller-cam motor, you would re-use your roller lifters and get a replacement roller cam. If you have a flat-tappet motor, you would get a cam-lifters package.

    An engine is an air pump. The more efficiently you can get air into it, the better it will run. However, you cannot really improve the intake if the exhaust is restricted. The more exhaust you start producing with engine upgrades will just make it back-up in the exhaust even more.

    The FIRST performance inprovement should ALWAYS be exhaust. You just can't get more air through it unless you get the waste OUT of it.

    As far as cams, after you have the exhaust switched around.....like I mentioned - CompCams Xtreme Marine: http://www.compcams.com/catalog/COMP...12_136-183.pdf

    Or, you might just use Edelbrock's Performer-cam along with the intake??
    Last edited by Beer:30; 10-06-2012 at 08:56 PM.
    Quote Originally Posted by gn7 View Post
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    I used this one on a customers earlier this year. It was a mild but solid build. He loves it. Has a good thimp but starts pulling about 2500 rpm. He is loving it.

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    Thanks guys, Sorry i didn't give a real good discription of what it is i have, its a old volvo penta (late 70's style). Im not sure of the stock horsepower but it's in 77 SCHIADA 22' cruiser with a volvo 280 drive. Im pretty sure its not a roller, the motor is all stock with the stock exhaust manifolds. The boat runs good but im looking to get more performance and speed but it is just a cruiser, i know i'm limited with the equipment im working with. I want to change the exhaust to thru transom but the wife likes how quit it is, and there really exspensive from what i've seen. I've built many motors over the years, big blocks and small blocks but mostly for cars so im not a complete dumb ass, this is just a new area for me.
    Thanks

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    New here Beer:30's Avatar
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    Quote Originally Posted by Dano214 View Post
    Thanks guys, Sorry i didn't give a real good discription of what it is i have, its a old volvo penta (late 70's style). Im not sure of the stock horsepower but it's in 77 SCHIADA 22' cruiser with a volvo 280 drive. Im pretty sure its not a roller, the motor is all stock with the stock exhaust manifolds. The boat runs good but im looking to get more performance and speed but it is just a cruiser, i know i'm limited with the equipment im working with. I want to change the exhaust to thru transom but the wife likes how quit it is, and there really exspensive from what i've seen. I've built many motors over the years, big blocks and small blocks but mostly for cars so im not a complete dumb ass, this is just a new area for me.
    Thanks
    Well, sound and HP go hand in hand. Notice top-fuel cars run zoomies with no mufflers and barely any pipe?

    Going to thru-hull exhaust is not that expensive. You just cap-off the "Y" that comes up to the motor. Then just extend the hose from the elbows straight back to the new tips. You just have to cut the transom, seal the exposed wood, and bolt in some tips. You can get switchable tips that electrically go from straight-exhaust to muffled with the flick of a switch. But yeah, that's $1000.

    Another example - my friends have a 25' boat, similar to mine but 5' shorter. Same exact motor as mine. They have long "S" pipes that take their exhaust down below the swim-step and partially into the water. THEN, the previous owner bolted on FULL TIME muffler tips. So, it's REAL quiet. But, I outrun them all the time. I am a full 4-5 mph faster than them. Shouldn't be....THEY should outrun ME. My boat is much heavier and has more real estate in the water than them. But, their exhaust is VERY restricted and thus - holds the motor back from full output.

    I'm afraid you are stuck where you're at. If you don't change the exhaust, you won't get hardly any performance from any upgrades. As mentioned, it's already holding your combination back right now. It will only get worse if MORE exhaust is pushed through.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


    2001 SleekCraft 30' Heritage SSB, open-bow mid-cuddy. 496HO / Bravo-I.

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    Quote Originally Posted by Dano214 View Post
    Thanks guys, Sorry i didn't give a real good discription of what it is i have, its a old volvo penta (late 70's style). Im not sure of the stock horsepower but it's in 77 SCHIADA 22' cruiser with a volvo 280 drive. Im pretty sure its not a roller, the motor is all stock with the stock exhaust manifolds. The boat runs good but im looking to get more performance and speed but it is just a cruiser, i know i'm limited with the equipment im working with. I want to change the exhaust to thru transom but the wife likes how quit it is, and there really exspensive from what i've seen. I've built many motors over the years, big blocks and small blocks but mostly for cars so im not a complete dumb ass, this is just a new area for me.
    Thanks
    Thats alot of boat for a mild small block. Its alot of boat for a built small block!
    Like Beer said, if you don't get the restriction out of the exhaust, you'll be pissing into the wind with a cam change. Even the manifold will about to virtually nothing. You have to free up the exhuast FIRST! Also, with that much load, you don't want to get to carried away with the cam. You don't have the compression for it, and you need all the mid range power you can muster. RPM is not going to be your friend with that engine in that boat. If you managed to pickup 5 miles an hour on the top, you may hate the boats performance getting up to that speed.
    Its all a compromise, and with a small block in that boat, its all compromise. Carefull for what you aiming to achieve. It WILL have its down side.



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    Beer30- I've been trying to tell the wife that! well you know how that goes.... That all makes sense, so i guess i need to figure out the exhaust first. Are the stock exhaust manifolds restrictive or is it more that it exits through the drive?

    gn7- I know its alot of boat for the small block, i've thought about putting a big block or even converting it to a v-drive or putting a bravo drive on it but its about how much money you want to throw at it. Im not looking to run with the big boys just want to have a good solid cruiser and ski boat, turnkey all day long and if i can get 50- 55 that would be ok. I think the drive can only hang till 60mph from what i've heard?

    Thanks for the input.

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    Yes the manifolds are probably more than a little restrictive. They are simply the cork up stream of the thru the prop restriction. Between the exhaust manifolds, the compression, and the possibilty of reversion of water in the manifolds, you VERY limited to the camshafts that will be of any benefit to you, and even then, it will be a very modest gain.
    Hate to rain on your parade, but the fact is that its all a combination thing. No one part or even a couple parts is gong to make a big gain in your package. Its the age old story of trying to make power with a incomplete combo. I don't like telling people this, but I hate seeing money spent by disappointed people too.



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