[Question] small block chevy performance upgrades
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small block chevy performance upgrades

  1. #1
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    Default small block chevy performance upgrades

    i recently purchased a 2000 ultra lx with a 5.7 and alpha one drive (4 blade solas prop w/ 19p). its the 250 hp motor with no mods except a thru transom exhaust i recently built. i currently am running the stock 2 barrel carb. is it worth it to upgrade intake manifold and carb? ignition? i have heard that it doesnt make that much of a difference. i know im not going to end up with a rocketship but any more power and speed i can pick up would be nice. please help!! thanks!
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    I really don't think that you would see a noticable performance difference (speed wise) unless you changed the cam as well. Not if you did do a cam, carb, intake change, you could bring that little motor alive. The stock heads and exhaust would be the next hurdle.Picking up an extra 50-75 hp wouldn't be very difficult.





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    cfm
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    Performance increase is very noticeable. Planing will be much quicker and top end will go up too. Done many of these. A larger prop will have to be in the budget.

    If you heard it doesn't make a difference it's from people that haven't done it, or if they did, they did it to a big heavy boat that should really have a bigger motor.

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    Quote Originally Posted by cfm View Post
    Performance increase is very noticeable. Planing will be much quicker and top end will go up too. Done many of these. A larger prop will have to be in the budget.

    If you heard it doesn't make a difference it's from people that haven't done it, or if they did, they did it to a big heavy boat that should really have a bigger motor.
    x2- if it already has the vortec heads and a hyd. roller, you could swap in a better cam, and throw a manifold & carb on it, and
    be pleasently surprised!


    Out With The Old, In With The New.......Goodbye Blinding Acceleration, Hello Sustained High Speed (in comfort)

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    Quote Originally Posted by cfm View Post
    Performance increase is very noticeable. Planing will be much quicker and top end will go up too. Done many of these. A larger prop will have to be in the budget.

    If you heard it doesn't make a difference it's from people that haven't done it, or if they did, they did it to a big heavy boat that should really have a bigger motor.
    thanks, do you have any suggestions on carb and intake manifold? i was looking at the edelbrock performer and the holly 4150 600cfm.

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    Quote Originally Posted by Blowncat 509 View Post
    x2- if it already has the vortec heads and a hyd. roller, you could swap in a better cam, and throw a manifold & carb on it, and
    be pleasently surprised!
    assuming i do have the vortec heads,do you have any cam suggestions? thanks for the help guys!!

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    cfm
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    Quote Originally Posted by cmsconstruction805 View Post
    thanks, do you have any suggestions on carb and intake manifold? i was looking at the edelbrock performer and the holly 4150 600cfm.
    RPM or RPM Airgap. Not the Performer.
    Vac secondary okay - if you do go to a real light spring. Better is a mechanical secondary as you can totally control your speed. Some fast boats with vac secondaries can be hard to control exact speed in certain throttle positions once secondaries are open. It's better if they move to your input - not airflow. 600-650cfm is fine.

    GM Hot Cam, roller rockers, and spring upgrade for a whole 'nother experience - very popular with the small block marine guys. Against contrary belief, you can keep your stock manifolds at this level but I wouldn't. My rule of thumb is small blocks over 330hp need the better manifolds from Eddie Marine, Lightning, or etc for a little better performance and most importantly to get away from the chance of water being sucked back into the engine from cam overlap.

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    Quote Originally Posted by cmsconstruction805 View Post
    assuming i do have the vortec heads,do you have any cam suggestions? thanks for the help guys!!
    Being a 2000, you do have the Vortec motor. Already has the hyd roller cam set-up too.

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    thanks alot!! ill start trying to find my parts and ill keep u guys updated!!

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    Quote Originally Posted by cmsconstruction805 View Post
    i know im not going to end up with a rocketship but any more power and speed i can pick up would be nice. please help!! thanks!
    Depends on what you call a rocket.

    Cam, intake, carb (+ heads on the earlier pre-Vortec engines) exhaust on these have taken low 50mph boats to low/mid 60's. Mid 50mph boats to high 60's.

    Nice to have small boat that responds to each hp increase. Also nice to have a good base engine that responds to normal modifications.

    You'll have fun. Guaranteed.
    Last edited by cfm; 08-06-2011 at 05:31 AM. Reason: added exhaust

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    look on Racingjunk.com- tons of intakes and carbs for good deals-most people on there are real good people-just like here


    Out With The Old, In With The New.......Goodbye Blinding Acceleration, Hello Sustained High Speed (in comfort)

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