Vacuum pumps on jetboats
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Vacuum pumps on jetboats

  1. #1
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    Default Vacuum pumps on jetboats

    I recently bought a 396 sbc stroker from a buddy. He had it built put it in a drag car made a few passes with it and lost interest.

    I am am in the process of freshing it up, changing the cam and a few other things so I can put it in my aluminum jetboat. He said it always wanted to blow out intake gaskets so he put breathers in the valve covers with lines running to the exhaust to remove the pressure. I don't want to do this on a boat.

    What are my options, no pcv, will a catch can work? Or do I need to get a vacuum pump?

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    So you think there is so much pressure in the lifter vally that it's blowing intake gaskets ??

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    Senior Member BGMAN's Avatar
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    I'm not an engine builder, but here are my $.02. I've never seen an actual intake gasket (gasket between head and manifold) "blow out", but I have seen the rubber or cork gasket piece between the valley blow out and cause an oil leak. Because of that, I never use the provided valley piece and just use black RTV. If it's truly blowing the gasket out between the heads then there is something else going on. You did mention that it was a fresh motor with only a few passes on it so maybe the rings never seated and it's creating a bunch of crank case pressure?

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    Quote Originally Posted by BGMAN View Post
    I'm not an engine builder, but here are my $.02. I've never seen an actual intake gasket (gasket between head and manifold) "blow out", but I have seen the rubber or cork gasket piece between the valley blow out and cause an oil leak. Because of that, I never use the provided valley piece and just use black RTV. If it's truly blowing the gasket out between the heads then there is something else going on. You did mention that it was a fresh motor with only a few passes on it so maybe the rings never seated and it's creating a bunch of crank case pressure?
    It was dyno'ed before he installed it, so it should be pretty much broken in. I have been in contact with the engine builder some, he is a drag racing guy and has limited knowledge on jet boats. He is actually the one who suggested the vacuum pump, but I haven't ever seen one in a boat.

    The guy who built this is very well known in my area, I have no doubt what he is suggesting to me will work, but neither of us have done it before so we both want some opinions on it.

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    Quote Originally Posted by gator20-60 View Post
    It was dyno'ed before he installed it, so it should be pretty much broken in. I have been in contact with the engine builder some, he is a drag racing guy and has limited knowledge on jet boats. He is actually the one who suggested the vacuum pump, but I haven't ever seen one in a boat.

    The guy who built this is very well known in my area, I have no doubt what he is suggesting to me will work, but neither of us have done it before so we both want some opinions on it.
    Where is the gasket failing?...Do you have a Pic?....never heard of blown intake gasket, except a blown up engine

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    southwindsforsure justsquirtin's Avatar
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    this is on my boat
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  9. #7
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    Quote Originally Posted by justsquirtin View Post
    this is on my boat
    Do you mind telling me a little more about your setup? What kind of pump? How much vacuum? Is it reliable?

    The guy I bought it from told me it will push the rubber end seals out from under the intake, no matter how much silicone is on them. But after he installed the breathers and the lines to the exhaust it stopped.

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    Senior Member jetboatperformance's Avatar
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    Haven't used traditional manifold end seals on anything in years, first check for fitment (manifold to block and heads) then maybe give thought to punch/peen the ends of the block and mating surfaces on the intake manifold and try a product like right stuff vs supplied end seals. Excess crankcase pressure from worn parts or excessively loose clearances, piston/ring type or design etc can obviously create the issue you describe , assuming the engine has adequate breathers to begin with, think I'd consider running a cylinder leak down and wet/dry compression to determine why amd try to correct the condition (blow by and crankcase pressure ) vs trying to control it on an NA deal

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    Check the angle of the head surface and the intake surface. Also make sure the intake bolts don't bind up in the intake bolt holes. This will keep the intake from crushing the gasket enough.
    QE 2050 W/ a Junk ass screw blower

    90% of the game is half mental... The pursuit of the unknown is priceless & gratifying . Sometimes it just takes good old fashion balls. No amount of reasoning or evaluation can deem it right or wrong. At the end of the day stick with whatever gives the person in question morning wood LOL

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    Ain't Right Racin piston in the wind's Avatar
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    Quote Originally Posted by jetboatperformance View Post
    Haven't used traditional manifold end seals on anything in years, first check for fitment (manifold to block and heads then maybe give thought to punch/peen the ends of the block and mating surfaces on the intake manifold and try a product like right stuff vs end seals , excess crankcase pressure from worn parts or excessively loose clearances, piston/ring type or design etc can obviously create the issue you describe , assuming the engine has adequate breathers to begin with, think I'd consider running a cylinder leak down and wet/dry compression to determine why amd try to correct the condition (blow by and crankcase pressure ) vs trying to control it on an NA deal


    You beat me to it
    QE 2050 W/ a Junk ass screw blower

    90% of the game is half mental... The pursuit of the unknown is priceless & gratifying . Sometimes it just takes good old fashion balls. No amount of reasoning or evaluation can deem it right or wrong. At the end of the day stick with whatever gives the person in question morning wood LOL

  13. #11
    southwindsforsure justsquirtin's Avatar
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    Quote Originally Posted by gator20-60 View Post
    Do you mind telling me a little more about your setup? What kind of pump? How much vacuum? Is it reliable?

    The guy I bought it from told me it will push the rubber end seals out from under the intake, no matter how much silicone is on them. But after he installed the breathers and the lines to the exhaust it stopped.
    I will get info on pump this afternoon
    it is adjustable on the vacuum-running 3to 5 right now
    this motor came from another boat and had no issues

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    If the manifold fits the head and block correctly and you use felpro gaskets and good silicone I like permatex ultra gray and not cork or rubber end seals and it actuly blows the shit out (venting the motor to atmosphere) you have big problomes

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