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Thread: How to tell intake and exhaust valve with the intake manifold on?

  1. #1
    BSAKing
    Guest BSAKing's Avatar

    Default How to tell intake and exhaust valve with the intake manifold on?

    I had a heck of a noise going on in my 350 V8 chevy engine. I checked
    it out and one of the rocker arms was quite loose.

    I am reading up on how to set the clearance on the lifters. I snag #1
    cyl and get it at TDC using the marks on the flywheel. I can tell the
    cyl # by the stamp on the engine block. Then I can set certain exhaust
    and intakes to proper clearance. No problem since all the cylinder
    numbers are marked on the head.

    1. BUT how do I tell which is exhaust and which is the intake valve
    with the intake manifold on? Been looking in the book and I see no
    info on that.

    Then I move and set it for #6 cyl and then do the rest of the rocker
    settings.

    2. Been wondering how come that rocker was so loose. As I understand
    it, the hydraulic lifter is just an oil filled damper chamber to take
    up erratic slackness within fine limits. If it was stuck it would make
    a clicking noise, but would not be THAT loose? Or do I misunderstand?

    thx BSA

  2. #2
    Steve W.
    Guest Steve W.'s Avatar

    Default How to tell intake and exhaust valve with the intake manifold on?

    BSAKing wrote:
    > I had a heck of a noise going on in my 350 V8 chevy engine. I checked
    > it out and one of the rocker arms was quite loose.
    >
    > I am reading up on how to set the clearance on the lifters. I snag #1
    > cyl and get it at TDC using the marks on the flywheel. I can tell the
    > cyl # by the stamp on the engine block. Then I can set certain exhaust
    > and intakes to proper clearance. No problem since all the cylinder
    > numbers are marked on the head.
    >
    > 1. BUT how do I tell which is exhaust and which is the intake valve
    > with the intake manifold on? Been looking in the book and I see no
    > info on that.


    With the valve cover off this is VERY easy. Take a look at the exhaust
    manifold. Notice how there are three sections that bolt to the head?
    They are almost exactly in line with the exhaust valves. One on each end
    and two in the middle.


    >
    > Then I move and set it for #6 cyl and then do the rest of the rocker
    > settings.
    >
    > 2. Been wondering how come that rocker was so loose. As I understand
    > it, the hydraulic lifter is just an oil filled damper chamber to take
    > up erratic slackness within fine limits. If it was stuck it would make
    > a clicking noise, but would not be THAT loose? Or do I misunderstand?


    A bad lifter can collapse and cause the rocker to become very loose. It
    also will NOT repair itself. You need to actually open the engine up and
    replace/repair the bad lifter. It could also mean that the cam lobe has
    ground down. The way to check that is with a dial indicator. You place
    it on a good rocker for the same valve (intake for intake and exhaust
    for exhaust) and see how far it travels then put it on the ? one and see
    how far that one moves, it should move almost exactly the same amount
    (almost because you will have some differences depending on the
    lifter/lobe wear)
    Another item on SBCs is that on the older engines with press in rocker
    studs they can pull out of the head over time, causing a loose rocker
    and then you need to reinstall it and pin it OR use a screw in stud
    conversion kit.

    >
    > thx BSA


    --
    Steve W.

  3. #3
    BSAKing
    Guest BSAKing's Avatar

    Default How to tell intake and exhaust valve with the intake manifold on?

    Hi - all this great info has given me food for thought.

    When I tightened the other rockers - it was only a smidgen - like
    maybe 1/8 turn at most just take a bit of slop out - some I actually
    loosened a tad. Just to get them sounding quite similar with just a
    'little' noise on each thru a garden hose. (I know - I can hear the
    purists and experts cringing... lol, but I did not know any better)

    That one noisy one though I had to turn a bit and now you have me
    worried. lol.

    I think I'll get some Sea Foam and run it through - it may loosen that
    one and then I can re-adjust. All I can say is that from the limited
    bit that I drove it - it was a lot smoother for sure....

    It is a 1976 corvette l-48 350 smogger - with about 125K miles on it.
    Never been opened up. FWIW, I usually do my own oil changes and I have
    never seen any metal grounds or debris in it....

    I'll try the loosening route first with Sea Foam (it sounds like a
    highly recommended product from what I read on the web) - if no go,
    then I guess I will have to gird my loins and pull the intake
    manifold. I am just a weekend mechanic and have never done any heavy
    duty engine work, so let's try the obvious first - that seems to make
    the most sense.

    Thanks for all the great info - REALLY helpful!

    BSA

  4. #4
    jim
    Guest jim's Avatar

    Default How to tell intake and exhaust valve with the intake manifold on?

    BSAKing wrote:
    >
    > Hi - all this great info has given me food for thought.
    >
    > When I tightened the other rockers - it was only a smidgen - like
    > maybe 1/8 turn at most just take a bit of slop out - some I actually
    > loosened a tad. Just to get them sounding quite similar with just a
    > 'little' noise on each thru a garden hose. (I know - I can hear the
    > purists and experts cringing... lol, but I did not know any better)
    >
    > That one noisy one though I had to turn a bit and now you have me
    > worried. lol.
    >
    > I think I'll get some Sea Foam and run it through - it may loosen that
    > one and then I can re-adjust. All I can say is that from the limited
    > bit that I drove it - it was a lot smoother for sure....
    >
    > It is a 1976 corvette l-48 350 smogger - with about 125K miles on it.
    > Never been opened up. FWIW, I usually do my own oil changes and I have
    > never seen any metal grounds or debris in it....


    Bad cams were common in that era - although you would think the bad ones
    would have been weeded out by now.
    If it is the cam lobe worn down you should be able to see that valve not
    moving as much as the others. And if it is a bad cam the clacking will
    be back fairly soon - they wear pretty fast once they start.

    Changing the cam is not that hard and they should still be some
    available in junk yards.

    -jim



    >
    > I'll try the loosening route first with Sea Foam (it sounds like a
    > highly recommended product from what I read on the web) - if no go,
    > then I guess I will have to gird my loins and pull the intake
    > manifold. I am just a weekend mechanic and have never done any heavy
    > duty engine work, so let's try the obvious first - that seems to make
    > the most sense.
    >
    > Thanks for all the great info - REALLY helpful!
    >
    > BSA

  5. #5
    Ed Treijs
    Guest Ed Treijs's Avatar

    Default How to tell intake and exhaust valve with the intake manifold on?

    On Apr 13, 5:29.pm, Ed Treijs <ed.toro...@..........> wrote:

    > 3) Make
    > sure all ancillary vacuum lines, plug wires, etc. are in good shape,
    > pull the distributor cap to make sure everything looks good, and put
    > on a timing light to ensure that timing is right, and vacuum and
    > centrifugical advance are functioning properly;


    I just want to make clear that this choice has nothing to do with
    fixing or not fixing a noisy valvetrain. It's a general check for a
    smog engine. The vacuum lines can crack; lubricant can dry up, etc.

    Also, don't discount an exhaust gasket leak as the real culprit. Does
    it get less noisy as the engine warms up? Leaks tend to do that.

  6. #6
    ben91932
    Guest ben91932's Avatar

    Default How to tell intake and exhaust valve with the intake manifold on?


    > 1. BUT how do I tell which is exhaust and which is the intake valve
    > with the intake manifold on? Been looking in the book and I see no
    > info on that.
    >


    E II EE II E

    HTH and good luck,

    Ben

  7. #7
    BSAKing
    Guest BSAKing's Avatar

    Default How to tell intake and exhaust valve with the intake manifold on?

    You must mean a Dial Indicator

    Exactly! One of dose dere tings. Thanks for the correction! That's
    exactly what it was.

    I now have the A/C, alternator, distributor, intake, carb etc off and
    have to disconnect the rad and get the fan shroud out of there before
    pulling the engine. Should be fun! I have never done any of this
    before....

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