Is this motor a good replacement SB?
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Is this motor a good replacement SB?

  1. #1
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    Default Is this motor a good replacement SB?

    I am looking to repower my 21' Mariah with a new motor.

    GM Performance 88958604 GM Performance Parts 350 Fast Burn 400HP Limited Late Model Engine

    I found the following motor and was wondering if it would be a good candidate?

    The peak HP and torque seems to be in the correct RPM range. May have to add new ignition box MSD to increase the stock REV limiter.

    Wondering if Forged Pistons would be necessary?

    Thanks

    Thanks

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    Boat engines typically spend more time under higher load than even circle track cars. A good first step would be to find out what the main and rod brg clearances the engine you are considering was built with and then compare to recommended marine clearances. As for pistons, for pleasure use the hypereutectic pistons would probably be Ok but suggest you get input from someone with more experience than I on that. Personally, I have always used forged pistons on every modified engine I build. Have you considered if you have oil pan clearance with the exisitng pan? It could be a good choice just suggesting you do a little more homework.

  4. #3
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    That looks good. I'd do it. Can't go wrong with a sbc. Might check out summits blueprint sbc crate engines. They are dyno proven. reliable is important.

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    Not bad...but did you notice the externally balanced flywheel?


    Also, make sure your dizzy has a bronze gear.
    Last edited by FormulaZR; 06-06-2011 at 10:12 AM.


    "No, my boat doesn't need any more power" - No one ever

  7. #5
    Some guy obnoxious001's Avatar
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    Quote Originally Posted by TexasRpm View Post
    I am looking to repower my 21' Mariah with a new motor.

    GM Performance 88958604 GM Performance Parts 350 Fast Burn 400HP Limited Late Model Engine

    I found the following motor and was wondering if it would be a good candidate?

    The peak HP and torque seems to be in the correct RPM range. May have to add new ignition box MSD to increase the stock REV limiter.

    Wondering if Forged Pistons would be necessary?

    Thanks

    Thanks
    If you read the GM description of the engine, I suspect there is a statement to the effect of "not for marine use", as with many of their engines. The key difference is that the clearances need to be different for a marine engine, where the engine block is kept cooler than a street engine, and the pistons are hotter from being run at constant higher RPM and load.

    People do run GM crate engines in boats, and they can work out, but it wouldn't be my first choice.

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    Default Question?

    I don' quite understand the issue concerning the clearance difference between a car race engine and a performance boat. Engines that I have built in the past for instance I have always for instance gauged between .020 and .030 on the main bearing caps. What would the clearance be for a Perf SB boat motor?


    I am in no way a pro so excuse me if I am way off on some things. I have only built a total of two motors one for my 69 camaro and one rebuilt on my Corvette L48 never a motor for a boat.



    Thanks

  9. #7
    gn7
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    Quote Originally Posted by TexasRpm View Post
    I don' quite understand the issue concerning the clearance difference between a car race engine and a performance boat. Engines that I have built in the past for instance I have always for instance gauged between .020 and .030 on the main bearing caps. What would the clearance be for a Perf SB boat motor?


    I am in no way a pro so excuse me if I am way off on some things. I have only built a total of two motors one for my 69 camaro and one rebuilt on my Corvette L48 never a motor for a boat.



    Thanks
    Its not so much the bearing clearances, as it is the piston to wall clearances and the rings gaps. Read these installation sheets and you may get the idea. Hyper pistons aren't the best choice for a marine engine running that kind of power level. Hypers are better than standard cast, but even a economy forging is a better choice.
    depending on how hard you intend to run the engine, the exhaust valves can be a little suspect as well.

    There is a reason marine replacement engines cost more money than car engines. But it never stops anyone from trying because the $$$$ suck them in.
    Wonder how much you save if you stick a ring, or bust a piston skirt, or drop an exhaust valve.

    CLICK: SRP/JE Piston clearances
    CLICK: KB hyper piston learances.



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    Last edited by gn7; 06-06-2011 at 05:10 PM.

  10. #8
    Some guy obnoxious001's Avatar
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    Quote Originally Posted by TexasRpm View Post
    I don' quite understand the issue concerning the clearance difference between a car race engine and a performance boat. Engines that I have built in the past for instance I have always for instance gauged between .020 and .030 on the main bearing caps. What would the clearance be for a Perf SB boat motor?


    I am in no way a pro so excuse me if I am way off on some things. I have only built a total of two motors one for my 69 camaro and one rebuilt on my Corvette L48 never a motor for a boat.



    Thanks

    I was going to ask if you didn't want to consider rebuilding what you have, but if you have built a couple of engines before, no reason you can't build one yourself. Small blocks are very inexpensive to buy cores for,, so if the boat is still running,, so why not buy a core block and put something together and then swap it out?

    As GN7 mentioned, you will want to research piston to wall clearance, since a marine engine block stays cooler than a race car running a radiator, but the pistons are still hot from running sustained higher loads and RPM.

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