why and what to do about crankcase pressure
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why and what to do about crankcase pressure

  1. #1
    Member dopeyest1's Avatar
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    Default why and what to do about crankcase pressure

    Finally got a day off to take the boat out for 1st time since installing the new tunnelram setup. After a small bit of tweeking, woooooohooooo!! damn what a difference. Did a bit of tearing it up and decided to stop for a bit in a vacant cove and give everything a quick once over and SHIT oil all over the place.
    Well after wiping things down and some closer inspection we discovered it was blowing back out dipstick and breathers at a very messy rate of speed.
    I have read that this is pretty normal when running tunnerams (not sure why) but what the heck is the best cure?
    460 Ford - basically stock - mild cam.
    Any help would sure be appreciated. Weather is finally to damn nice here to be cleaning - time to be terrorizing Thanks
    If it's petty, don't sweat it - If it's sweaty, don't pet it

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    Senior Member jetboatperformance's Avatar
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    Aside from a potential for a possible overfilled crankcase , I'd start with a compression wet and dry compression test and cylinder leakdown test at minimum pull the plugs and read them ... Tom

  4. #3
    Senior Member Uncle Dave's Avatar
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    It isnt just worn out engines, or engines with a bad valve that can do it.

    Fresh engines and efficient roller cams generate a lot of crankcase pressure.

    (Providing everythings actually right.)

    I had to switch to dual breather speedway style valve covers for my 500hp 406.

    If you dont relieve that pressure you will start pushing out gaskets and thats bad....


    Uncle Dave
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    Last edited by Uncle Dave; 07-15-2010 at 10:47 PM.

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    I am new to jetboating but I'm not new to high performance engines. On a few motors I've built I have had to run a crankcase evac system to relive psi. It is essintualy a hose in each valve cover that runs to your headers to pull the psi. out. I'm not sure if this would work on a jet or not due to the water system. A kit could be had from just about any mail order catalouge for around 50$.

  7. #5
    mo balls than $cents$ IMPATIENT 1's Avatar
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    no leaky leaky when i built this motor, at least not from crankcase pressure lol

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    TRG
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    is it necessary to run two lines from the V/C's? Is one from the rear of the V/C to a breather canister sufficient?

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    21 Daytona Outlaw's Avatar
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    Quote Originally Posted by TRG View Post
    is it necessary to run two lines from the V/C's? Is one from the rear of the V/C to a breather canister sufficient?

    It is if you're from Oklahoma

    it looks to me that that system would pull air thru the breathers on the tank
    and out the vc's
    #55

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    Senior Member Widetrack's Avatar
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    Quote Originally Posted by Outlaw View Post
    It is if you're from Oklahoma

    it looks to me that that system would pull air thru the breathers on the tank
    and out the vc's
    I have one like Tom's and no problems! But I don't run evac system!
    [IMG][/IMG]
    I put a drain line on mine to catch the drippings when time to drain! WT
    Last edited by Widetrack; 07-16-2010 at 08:10 AM.


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    Horsepower sells Engines lefty's pride's Avatar
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    i often wonder about those flame arrestors with the dual ports i kinda have the same issue with mine
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    Last edited by lefty's pride; 07-17-2010 at 12:45 AM.
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    Senior Member Schiada 201's Avatar
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    I put a fitting for a line to a puke tank from the pan. This seems to relieve the pressure at least from mine. Also put large Canton valve covers, a piece of vac hose for the dip stick.

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    Member dopeyest1's Avatar
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    Well here is what I am trying 1st --- There are now 3 breathers on the valve covers. 2 of them now have the "baffle style" groments in them, the other has an open groment as it will still be the oil fill as well. I compared all 3 breathers and put the one with the tightest bend in the flap inside the opening hoping maybe it would help.
    I am thinking that after realizing the the baffle style groments exsisted and now it isn't a nice unimpeded straight shot off the rockers that things will be all better. Oh ya - also have a rubber carb vent cover that will fit snugly over the dip stick tube if it still wants to fling oil.
    Here where I live in Idaho, if the word "performance" is anywhere even closely involved with a part you can flat forget about finding in stock here so this was about the only route I had the option of and still making the lake this weekend.
    Will let you know how it goes
    Last edited by dopeyest1; 07-17-2010 at 03:42 AM.
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    21 Daytona Outlaw's Avatar
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    Quote Originally Posted by Widetrack View Post
    I have one like Tom's and no problems! But I don't run evac system!
    [IMG][/IMG]
    I put a drain line on mine to catch the drippings when time to drain! WT
    Yeah to me the evac system is in the wrong spot, If it was me I would hook the evac to the tank, this would pull from the engine to the tank.

    to me it looks like the tank is just a breather not a catch can. IMO
    #55

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