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Keep sucking Oil past the Intake gaskets

This is a discussion on Keep sucking Oil past the Intake gaskets within the Technical / Maintenance forums, part of the General Discussion category; Hi, A year ago I put in a new 350 Engine into my pickup. The engine is a rebuilt 86 ...

  1. #1
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    Keep sucking Oil past the Intake gaskets


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    Hi,

    A year ago I put in a new 350 Engine into my pickup. The engine is a rebuilt 86 350. I'm running a new Edelbrock Perfromer Intake and stock heads.

    The problem is that I keep losing the seal on my intake gaskets and sucking Oil into the intake ports from the lifter valley. This is the third time I've ruined a set of gaskets in a year. I can change the gaskets and it will run great for as long as I stay out of the bush. As soon as I come down a steep grade on compression it will start to burn oil and then after that it will burn oil at anytime on compression. Alot of Oil, over a quart in a 1000 Miles.

    Any ideas on what I can do to fix this? I have used 2 sets of Felpro gaskets and one set of Mr Gasket. I have glued them in and I have syliconed them in and I have put them in with no sealants.

    I'm thinking maybe these heads were milled and are now off angle to the intake flange. Any other ideas? I do have a set of 441 heads I could get rebuit and put on in place of these smoggers (642 or something like that). I'd rather not though.

  2. #2
    GMC RULZZ NEUMANNZZ's Avatar
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    Re: Keep sucking Oil past the Intake gaskets

    do you have valve cover breathers or are you using a pcv valve and a hose going to the airfilter or nothing(which might be causing the problem)?
    Last edited by NEUMANNZZ; 10-08-2006 at 05:31 PM.
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
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    Re: Keep sucking Oil past the Intake gaskets

    I have a PCV valve and hose running to the Carb on one valve cover while the other valve cover has a breather/Oil fill plug.

    The PCV was replaced at the same time I did the engine. I can't garrantee that the breather works at all since it is a made in china piece same as my valve covers.

    I wanted to add that my intake in a Non-EGR intake.
    Last edited by Markus1; 10-08-2006 at 05:56 PM.

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    Re: Keep sucking Oil past the Intake gaskets

    I checked out my breather on the valve covers last night and it works fine.

    I did however think of something else.

    When I put the engine in I turned the idle right down, not the idle mixture screws but I closed the primary butterfly's all the way to give it a nice quiet slow idle.

    I'm thinking that when under compression the engine is making so much vaccuum with no place to go it sucks past te intake gaskets. If I turn up the idle a slight bit to open those butterfly's a little that might get rid of enough of the vaccuum to stop from ruining gaskets.

    I know this is sort of a common problem on Chevy's.

  5. #5
    technut
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    Re: Keep sucking Oil past the Intake gaskets

    do you notice that the top of the gasket is super compressed
    and the lower part isnt? possible decked block, milled cylinder
    heads or both. this would cause the mal-sealing at the bottom
    as the intake rests on the block before the cylinder head
    surfaces.the intake to block seal is compressed thin, cut or non-
    existant? if so again, check with your machine shop about this
    sealing issue you have for the past year...
    as for hi-vacuum... c'mon @ 20" of vacuum isnt going to move
    .080" pressed paper properly sandwiched and torqued...
    compression has nothing to do with intake port filling. itd
    be the intake stroke thatd be suspect... and isnt a common
    chevrolet problem.

    airdeano
    2001 Silverado 4.8L 4-spd Automatic 3.42
    ? horsepower
    ? torque
    will find out soon!

    1965 C10 5.3L (SSR) TH4L60e
    (It's Alive! 07/04 It Drives! 03/05 Daily Driver XX/08!)

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    Re: Keep sucking Oil past the Intake gaskets

    I havn't closely inspected the gasket to see if the top is super compressed and the bottom not.

    There is still probably an eight inch clearance between the bottom of the intake and the top of the block.

    The problem only arrises coming down hill on compression/hold back... foot completely off the gas and running down in 4th gear(manual Tranny) then she burns Oil. If I change the gaskets it will be fine for a long time until I come down something quite steep in say 2nd gear and then it will happen consistantly.

    I did however turn up my idle a couple days ago and the highway smoking has gone away but I havn't gone out into the bush since.

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    Re: Keep sucking Oil past the Intake gaskets

    sounds more like valve seals ???

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    technut
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    Re: Keep sucking Oil past the Intake gaskets

    im with chevyman, on decel (this would be more common) that
    20-21" of manifold vacuum would draw engine oil from the intake
    valve seals. opening the throttle for more idle would decrease
    this vacuum signal. so if the problem is only decel id lean
    more towards intake valve seals than intake manifold as youve
    suggested. but without inspection of the gasket its anybodys
    guess...

    airdeano
    2001 Silverado 4.8L 4-spd Automatic 3.42
    ? horsepower
    ? torque
    will find out soon!

    1965 C10 5.3L (SSR) TH4L60e
    (It's Alive! 07/04 It Drives! 03/05 Daily Driver XX/08!)

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    Re: Keep sucking Oil past the Intake gaskets

    I've changed the gaskets twice now and both times they were drenched in oil. I could clearly see that oil was getting past the gaskets into the intake ports. The gaskets were not cracked or torn. The Oil was coming in between the gaskets and head and intake flanges.

    The Oil with out doubt is coming in past the gaskets.

    The problem is much better now since I have opened up the primary's.

    I have a good quality set of perfromance gaskets coming.

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    Re: Keep sucking Oil past the Intake gaskets

    It works great as long as you stay out of the "bush"? Damn. I've never seen an automobile that took exception to a man getting a little bush and then punished him for getting some.

    But I've had some girlfriends who did that a lot.

    LF
    Love my one ton dually for fishing and hunting.

 

 

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