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  1. #1
    Join Date
    Apr 2008
    Location
    Posts
    52

    Default "I decided I would perform a c

    "I decided I would perform a compression test before sinking any money into manifolds and risers on my pair of 440s. All going OK until I got a 30psi reading on one of the cylinders. I ran the motor up to temp and up to 2500rpm to break any crud free if it was just a sticky valve. I also put oil into cylinder to see if that would temporarily seal a bad ring. Only got up to 45psi with oil, then back to 30psi after running motor. Lots of blow by from rocker cover also. Engine runs OK but a bit smokey from exhaust and rocker cover. Any words of encouragement would be appreciated.
    Eddie Zuskin"

  2. #2

    Default "A compression leak down test

    "A compression leak down test can help you isolate
    an intake,or exhaust valve leak or piston blowby.
    A couple things it may be are. Stuck open valve,Burnt valve, head gasket, not likly piston or ring damage. As I reread your statement.
    I would pull valve cover. look for broken valve spring. If not time to pull cyl head and inspect"

  3. #3
    Join Date
    Apr 2008
    Location
    Posts
    52

    Default "David, Thanks for taking tim

    "David,
    Thanks for taking time to reply. I am willing to perform leakdown, then pull valve cover or even pull intake and cylinder head. That's about the limit of my engine building skills. I replaced the heads(one was cracked from blown headgasket) on a small block GM mercruiser, and twice on a 4cyl DOHC Lotus motor. So I am not in "Panic Mode" until those skills are exhausted.

    Why "not likely piston or ring damage?" Would pieces of metal be making noises?
    Regards,
    Eddie"

  4. #4

    Default It just doen't sound like

    It just doen't sound like piston damage.

  5. #5
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    15,190

    Default "Bad rings would be my guess s

    "Bad rings would be my guess since the oil raised the compression a bit, then it went away.

    Jeff"

  6. #6

    Default "30 psi+ oil= I would expe

    "30 psi+ oil= I would expect to see 80 to 130 psi.
    Unless damaged piston? less likely.
    My thought. blow by one rocker cover?= Compression up the valve stem of the open,bent,or burnt valve.
    Let us know
    Thanks"

  7. #7
    Join Date
    Apr 2008
    Location
    Posts
    52

    Default Any way to determine valve iss

    Any way to determine valve issue by just pulling valve cover?

  8. #8
    Join Date
    Jul 2006
    Location
    Redmond, WA, USA
    Posts
    216

    Default "It's a valve. The compres

    "It's a valve. The compression would have gone way up with the oil you added if it was a ring. The head is very easy to get off, pull both and take them to your local machine shop."

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