400 SBC for a jet
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400 SBC for a jet

  1. #1
    Senior Member Chop Shop's Avatar
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    Default 400 SBC for a jet

    I am looking to get some advice about my engine plan for my boat.

    First my plan.

    I have a SBC 350 in my boat now. It needs more power and my current 350 has way too much end thrust play in the crank. I am going to put a BBC in the next summer or two. I dont have the cash (new house) to build a BBC this year but I want to put the blower on this year and learn a little more about boost before i spend big coin on the 496 low end.

    I have a 671 blower. I have a SBC and BBC intake manifold for the 671.

    I would like to put a 400SBC in for this summer and then swap out to a 496 in years to come.

    So, I AM going to install a 400 before summer with a blower on top.

    Do I,,,,,,

    Get a decent used engine and put a set of decent heads on and just run it? A stock 400 is going to have a stock CR in the same range as a blower motor.

    Or,,,,,,,

    do I need to rebuild it and at least get forged pistons and a good crank?


    Its not getting raced or beat badly, just needs to run all summer on 92 octane.

    I would prefer to run a good used engine and put save cash for the big block swap.

    Is the 400 balancer and flexplate going to open up any problems?

    I know 400s have steam holes in the heads/block. Can I just drill out a set of normal heads and boltem on?



    I would like to keep this as cheap and simple as possible.

    (please refrain from telling me to just build the BBC and be done with it, its just not in the budget yet)


    Any ideas?

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    Senior Member rogerroost's Avatar
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    at this point(almost may),as you say ,just for this season ,I think used 400,nice cam,single plan manifold,good carb,don't know what you have for exhaust,but maybe some used o/t headers and run it
    save your money for the real motor

  4. #3
    Senior Member Chop Shop's Avatar
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    Boat has Borlas on it. I plan to put the 671 on the 400 for the season. Thats not going to change.

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    Senior Member rogerroost's Avatar
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    a blower on a stock ,and or used motor sounds like a frustrating & short season ,,,,just my 2 cents. good luck

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    Senior Member 67weiman's Avatar
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    Used 400 with a blower won't live long, Imho. I wouldn't put a huffer on unless you built a stout bottom end. Forged bottom end using a 5.7 or 6.0 " rod. The stock 5.57" 400 rods wore cylinder walls rather quickly.

    As for the flexplate, it would only be an issue if your pto was for a flywheel.

    In a boat, you would be ok not drilling the steam holes. You can drill them in any SBC head. The ones towards the intake side of head need to be drilled at an angle towards the water jacket in the head. I believe it is 30*.
    Last edited by 67weiman; 04-26-2012 at 06:59 PM.

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    Senior Member zacho!'s Avatar
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    Quote Originally Posted by 67weiman View Post
    Used 400 with a blower won't live long, Imho. I wouldn't put a huffer on unless you built a stout bottom end. Forged bottom end using a 5.7 or 6.0 " rod. The stock 5.57" 400 rods wore cylinder walls rather quickly.

    As for the flexplate, it would only be an issue if your pto was for a flywheel.

    In a boat, you would be ok not drilling the steam holes. You can drill them in any SBC head. The ones towards the intake side of head need to be drilled at an angle towards the water jacket in the head. I believe it is 30*.
    lol! when i first read this post I almost said "contact 67 weiman, he's got a sbc that runs!" just lazy...

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    Senior Member rpm0414's Avatar
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    I once built budget 400 for my drag car. Cast crank, 5.57 stock rods with ARP bolts, cheap dart sportmans heads, victor jr intake, [email protected] cam and it made nearly 500 hp and ran for 4 years. The last year I ran it I hit it with 250 shot of juice and it never broke. Great little motor!

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    Senior Member Chop Shop's Avatar
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    No other input?


    Any one running a blower on a STOCK lower end?

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    Senior Member jamesblown97's Avatar
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    well a 6-71 is not a big blower, pulley it to keep the boost down 6-8lbs and it should live for a while but if you want to put more boost to build the motor you want and put the boost to it. I had a pretty much stock small block that i put 9 lbs of boost to and it lasted a couple years i treated the motor pretty good but every now and then it got beat on.

  12. #10
    Resident Ford Nut Sleeper CP's Avatar
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    Quote Originally Posted by Chop Shop View Post
    No other input?


    Any one running a blower on a STOCK lower end?
    how much boost do you plan on running and what fuel?

    S CP
    Last edited by Sleeper CP; 04-29-2012 at 11:06 AM.

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  13. #11
    Senior Member Chop Shop's Avatar
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    Quote Originally Posted by Sleeper CP View Post
    how much boost do you plan on running and what fuel?

    S CP
    Low boost and pump gas. Whatever makes it last, look good and run decent.

    Im not planning to set any speed records or drag racing folks, but I have a blower on my bench and I want to see it on my boat.

    I plan to build a 496 for it next year that is capable of running hard and reliable. Until then I want to turn around a see a polished huffer in my boat.


    If I have to be nice to it, thats fine. I was just thinking of either tossing rings and bearings in my current 350 and put the 671 on it till next year. OR buying a decent used 400 and just putting the 671 on that for the year. I just figured the low compression of the 400 would play friendly with the blower.



    I have seen guys on the street in hotrods and muscle cars run a blower on a poser engine for years with no problems, just wanted to know if there is some big nono about doing it in a jetboat?

    I have dreamed of having a blower since I was a kid. Every monster truck way back then had a blower and 2 or 3 predators on top. I have a blower sitting here on my bench with a pair of predators on top and its killing me! I want to run it!

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    AIR POWER TAPPED OUT's Avatar
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    Whats the big deal about having a blower on it?, it's still going to be a slow mouse powered jet boat.

  15. #13
    Hoodys and swim trunks Elkidminoltu's Avatar
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    Bolt it on and go! Tune it fat, don't get crazy with timing and rock the hell out of it till it pops...if it does.

  16. #14
    Some guy obnoxious001's Avatar
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    Quote Originally Posted by Chop Shop View Post
    Low boost and pump gas. Whatever makes it last, look good and run decent.

    Im not planning to set any speed records or drag racing folks, but I have a blower on my bench and I want to see it on my boat.

    I plan to build a 496 for it next year that is capable of running hard and reliable. Until then I want to turn around a see a polished huffer in my boat.


    If I have to be nice to it, thats fine. I was just thinking of either tossing rings and bearings in my current 350 and put the 671 on it till next year. OR buying a decent used 400 and just putting the 671 on that for the year. I just figured the low compression of the 400 would play friendly with the blower.



    I have seen guys on the street in hotrods and muscle cars run a blower on a poser engine for years with no problems, just wanted to know if there is some big nono about doing it in a jetboat?

    I have dreamed of having a blower since I was a kid. Every monster truck way back then had a blower and 2 or 3 predators on top. I have a blower sitting here on my bench with a pair of predators on top and its killing me! I want to run it!
    Thing is,, you would be bolting power on an unknown, used 400 cu in engine. You don't necessarily think that you will run it hard in a boat, but RPM level in a jet boat is typically double what you might run on the street. If you freshen the 350, at least you will have seen what's in the bottom end. I would think about really low boost if you want to bolt the blower on for looks, on a stock type bottom end.

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