cheap speed

[Karl]

I've got a 21' Chris Craft with a 260/Alpha that does 56mph by the speedometer on what I believe is a stock 350. I am new to the scene and put a set of new Osco manifolds and risers on before I found out about available after market speed stuff. I would like to get input on hp improvement w/o removing my exhaust manifolds (I have thru transom exhaust). What I'm looking for is a cam / intake / ignition combination to maximize hp out of my 350 while using the orig exhaust. Any help or guidance would be cool.
Thx

[FastElim900]

Karl,
While there will be incremental improvements you can make you must realize that a gasoline reciprocating engine is basically a large air pump. The more air/fuel pumped in and subsequently out of the motor will determine how much power it will make. There isn't any magic. Improve airflow and increased power will result.

[crmax]

speedos in boats are all most always wrong, buy or borrow a gps write down what your rpms and mph are then come up with a plan ( how much more HP you will need) on how fast you want to go, by doing this you wont spend alot of money and not get where you want to be.

[Karl]

crmx,
I know this is stretching it, but I'd like to get 65 out of it. I agree with FastElim900 in that more mix through the system results in more hp. I figure a .462in/.477out (lift) roller cam from Comp Cams, a good dual plane intake, and a bigger flame arrestor would give me additional flow, and therefore more power and torque. But how much to expect is another story????? Several companies like Summit or PAW produce automotive "kits" depending on what HP you want and how much you want to spend. Isn't there a company or magazine that has tested similar marine combinations?

[69 Elim]

I think you've got it all wrong. Cheap & speed don't go together. Ya gotta pay to play. But if ya want to wake up that 350, here is an idea. I could tell you about heads, cam, intake, etc... but it much simplier just to drop in a crate motor - cost can usually be similar too. I think you would be happy with an honest 350hp to get you in the 65mph range.

[mister460]

69 is right. People talk about cubic inches but it really comes down to one thing: CUBIC DOLLARS! Or nitrous.

[crmax]

I agree save you money for a crate motor you be twice as happy in the long run

[77charger]

It is in my opinion cheaper to add to your current motor it will for sure be way cheaper if you can do the work yourself then you are talkina few hundred bucks.a complete crate motor will run some dough.The cam will be the biggest improvement.I would guess around 5-600 total you can find a used intake for cheap ignition wont bring alot of hp as you think.cam,compression and carb make hp.

[Karl]

I agree 77charger. All these people must not know how to do the work themselves (no offense). I can build a chevy motor for the street with my eyes closed. This is my first boat motor mod and want to know how different marine cam grinds are vs street cam grinds, and the best grind for a good dual plane and stock mercruiser exhaust manifolds.
I'm thinking a roller cam with Duration - 264 int, 270 ex. @.050" - 212 int, 218 ex.
Lift - .488 int, .495 ex.
112 degree lobe separation angle
I think this cam with a tall dual plane intake would get me well over 300 horses "with" the mercruiser manifolds and between 60-65.
Am I out of my mind?

[Havasu Hangin']

Well Karl...I'll throw my 2 cents in...
You can go with an aftermarket exhaust and still keep the through transom...
I would look at a good set of heads, if you don't have them already (w/2.02's and the 170-180cc intakes). With those, you'll do well with a Holley or Edelbock dual plane intake. As for the cam, the one you mentioned will work, but you could go a little bigger. Keep in mind that more duration will equal less final compression, though. That Alpha will need a good idle for shifting.
Most marine engines are built for torque, and HP just happens. So most marine recipes are closer to truck engines. Merc and other builders guard thier recipes pretty close.
Here's (http://www.amazon.com/exec/obidos/ASIN/1557883173/qid=1022261920/sr=2-1/ref=sr_2_1/103-8984719-3051031) some good reading to educate yourself on the difference between marine & auto recipes.
http://www.planetsmilies.com/smilies/happy/happy25.gif

[Essex502]

Is there such a thing as cheap speed?

[crmax]

dont say we didnt warn you, http://free.***boat.net/ubb/smile.gif by the time your done with boring the block for the higher compression pistons to run the bigger cam to breath enough air to run with the big blocks you could have a brand spanking new motor dropped off. but if you like doing it yourself go for it myself Im tired of working on my stuff all the time. by the way will 65 be fast enough?? it isnt for me Im thing about swapping out a 7.4 for a 502 cubic inches is the cheapest HP

[KTM]

Crmax,
Are you talking about the 500hp/502? I've seen them in jegs and summits magazines but they say not for marine use.
Where is the best place to get one and how much money?
Ken Originally posted by crmax:
dont say we didnt warn you, http://free.***boat.net/ubb/smile.gif by the time your done with boring the block for the higher compression pistons to run the bigger cam to breath enough air to run with the big blocks you could have a brand spanking new motor dropped off. but if you like doing it yourself go for it myself Im tired of working on my stuff all the time. by the way will 65 be fast enough?? it isnt for me Im thing about swapping out a 7.4 for a 502 cubic inches is the cheapest HP

[crmax]

there are a couple places online to get the marine version, I havent started price shopping yet I want to wait till my warrenty runs out and then sell mine and buy another

[KTM]

crmax,
If you know where at online to find them, please post sometime. I'm interested in checking them out vs. rebuiding my 7.4
Thanks,
Ken Originally posted by crmax:
there are a couple places online to get the marine version, I havent started price shopping yet I want to wait till my warrenty runs out and then sell mine and buy another