• Crankshaft and Journal question
  • Crankshaft and Journal question
  • Crankshaft and Journal question
  • Crankshaft and Journal question

Thanks Thanks:  0
Likes Likes:  0
Dislikes Dislikes:  0
Page 1 of 2 12 LastLast
Results 1 to 15 of 20
  1. #1
    brimis
    Guest

    Default Crankshaft and Journal question

    My 84 L83 started to "knock" about two weeks ago. Upon getting the car home I noticed the damper had split. Hoping this was the problem I removed the belt and damper and started the car only to here the same "knock". I should mention as I increase throttle the "knock" becomes faster and not louder. Oil pressure is fine, steady at 47 or so while parked in the driveway. I pulled the vavle covers and the pushrods and rocker arms appear to be fine, meaning the pushrods are moving and the rocker arms are moving freely, not to mention the "knock" did not get louder after removing the covers. I dropped the oil pan to check the connecting rods, caps, mains and journals. The mains appear to be fine. My questoin is how much if any should the connecting rods/caps move.
    I can grab the caps, 1/2, 3/4, 5/6 and 7/8 and move them ever so slightly left to right, but not up and down. How much "play" should there be on each journal?

  2. #2
    Member WhalePirot's Avatar
    Join Date
    May 2002
    Location
    SoCA
    Posts
    2,943
    Corvette(s)
    1984 White Z-51/ZF6-40/Shinoda body
    Post Thanks / Like
    Rides
    0

    Default

    I would listen for the knock while BRIEFLY running the engine with the serpentine belt off. The knock might not be internal.

  3. #3
    Member G Winter's Avatar
    Join Date
    Aug 2004
    Location
    NW Iowa
    Posts
    2,177
    Corvette(s)
    1990 red convert 6 sp
    Post Thanks / Like
    Rides
    0

    Default

    If your talking about end play, front to rear, then there would be just enough that you could feel it. Might want to check a manual for specs on
    the end play. What type of knock is it? hard knock , light knock, single or a double knock? Maybe a broken piston ? Is this by chance an auto. sometimes the flex plate will break. usually a light sounding knock .

  4. #4
    Gone but not forgotten Ken's Avatar
    Join Date
    Jan 2001
    Location
    Hermosa Beach, CA
    Posts
    8,237
    Corvette(s)
    1987 Z51 Silver Coupe
    Post Thanks / Like
    Rides
    0

    Default

    Quote Originally Posted by brimis
    ...ever so slightly
    Is that like "just a tad"?

    The rod bearing clearance should be .0013-.0035" from the factory, with service recommended at .0035" max, and a rod side clearance of .006-.014".

  5. #5
    Member G Winter's Avatar
    Join Date
    Aug 2004
    Location
    NW Iowa
    Posts
    2,177
    Corvette(s)
    1990 red convert 6 sp
    Post Thanks / Like
    Rides
    0

    Default

    Wow, Ken , .0035 seems lose to me. I think in the old days it was more like .0025 btw how you make that quote thing work ?

  6. #6
    Gone but not forgotten Ken's Avatar
    Join Date
    Jan 2001
    Location
    Hermosa Beach, CA
    Posts
    8,237
    Corvette(s)
    1987 Z51 Silver Coupe
    Post Thanks / Like
    Rides
    0

    Default

    .0035 is straight from the 1987 L-98 service manual. The 1990 L-98 was the same animal.

    Man, I hate it when I have to get back up from my chair, retrieve the book and look it up again, just to allay my fears that I mis-typed, transposed, or perhaps mis-read the numbers. I am so full of self-doubt.

  7. #7
    Member G Winter's Avatar
    Join Date
    Aug 2004
    Location
    NW Iowa
    Posts
    2,177
    Corvette(s)
    1990 red convert 6 sp
    Post Thanks / Like
    Rides
    0

    Default

    I wasn't doubting what you posted , just alluding to the fact that they are building that part of the engine loser. Maybe for gasmilage ?

    I will be more carefull on how I state things in the future, don't want you getting out of your chair for no reason.

  8. #8
    Member motorman's Avatar
    Join Date
    Mar 2002
    Location
    pa
    Posts
    849
    Corvette(s)
    2008 Crystal Red Tint Coat
    Post Thanks / Like
    Rides
    0

    Default

    Quote Originally Posted by brimis
    My 84 L83 started to "knock" about two weeks ago. Upon getting the car home I noticed the damper had split. Hoping this was the problem I removed the belt and damper and started the car only to here the same "knock". I should mention as I increase throttle the "knock" becomes faster and not louder. Oil pressure is fine, steady at 47 or so while parked in the driveway. I pulled the vavle covers and the pushrods and rocker arms appear to be fine, meaning the pushrods are moving and the rocker arms are moving freely, not to mention the "knock" did not get louder after removing the covers. I dropped the oil pan to check the connecting rods, caps, mains and journals. The mains appear to be fine. My questoin is how much if any should the connecting rods/caps move.
    I can grab the caps, 1/2, 3/4, 5/6 and 7/8 and move them ever so slightly left to right, but not up and down. How much "play" should there be on each journal?
    the split damper is a sign that the crank "MAY" be cracked. you also could have something on top of a piston. check your plugs for any sign of something hitting them. the side to side movement on a pair of rod should be .015 to.020
    retired race engine builder,former NASCAR tech inspector,corvette owner since 1959, new corvettes owned,59,62,63,64,65,66,97,99,02,05, 2008 is in my garage, 2008 sold and waiting for my C-7

  9. #9
    Banned SSTibet's Avatar
    Join Date
    Apr 2004
    Location
    Ankara TURKEY
    Posts
    722
    Corvette(s)
    1995 6 Speed Manual Coupe
    Post Thanks / Like
    Rides
    0

    Default Same here...

    Quote Originally Posted by Ken
    Man, I hate it when I have to get back up from my chair, retrieve the book and look it up again, just to allay my fears that I mis-typed, transposed, or perhaps mis-read the numbers. I am so full of self-doubt.
    Ken, do not hate this habit of yours; same personality here... I review my messages at least a few times before posting them and still edit the post once or twice... I have accepted the fact that this is my personality trait, and I think I like perfection. Perfection brings some stress but a lot of quality to the way we live. Our types plan to the finest detail before execution and likes avoiding surprising outcomes.

    And I am not going to give up my habits, they are what makes me who I am.

    Cheers buddy,

    Selim

  10. #10
    brimis
    Guest

    Default

    I did check for noise with the belt off and it is present. I pulled the plugs and they are white, very clean.

  11. #11
    tnovot
    Guest

    Default

    I think it would be a good idea to get a stethescope (or piece of rubber hose/tubing) to listen while the engine is running in order to more precisely locate the noise. Whale made a good point, the noise may not be internal.
    Is the oil pan still off? If so, maybe a good idea to pull the rod caps and visually inspect the bearing inserts. When you drained the oil, was there evidence of small metallic flakes in the oil or in the bottom of the pan?

  12. #12
    Member jmccloud's Avatar
    Join Date
    Feb 2003
    Location
    Maryland
    Posts
    694
    Corvette(s)
    1995 White Coupe LT-1 Auto
    Post Thanks / Like
    Rides
    0

    Default

    My sister-in-law once had a Nova small block (automatic trans) that developed a knock. Turned out to be a crack in the splice plate (the plate that connects the crank to the torque converter). Took us days and a stethescope (actually a piece of garden hose stuck in one ear) to locate the source.
    Sounded a lot like what you describe.

  13. #13
    Registered User
    Join Date
    Nov 2004
    Location
    louisiana
    Posts
    81
    Corvette(s)
    1997 Silver Coup
    Post Thanks / Like
    Rides
    0

    Default

    I'm with jmccloud on this one...if you did the belt thing and the cap checks, go for the flywheel. Several weeks ago, I bought a ford pickup that had a bad knock in it that drove me crazy for a day or two. My son seemed to think that the noise was comming from the tranny and we checked it. Now this was an automatic and we were able to pull the inspection plate...when I put the wrench on the first nut I was surprised that I could move the flywheel without loosening the nuts. Turns out that the flywheel was cracked and this was my problem. I later learned that those Ford 300's are bad about that. Give that a try...just might be your problem.

  14. #14
    vette-dude
    Guest

    Default

    Quote Originally Posted by Rufus1050
    I'm with jmccloud on this one...if you did the belt thing and the cap checks, go for the flywheel. Several weeks ago, I bought a ford pickup that had a bad knock in it that drove me crazy for a day or two. My son seemed to think that the noise was comming from the tranny and we checked it. Now this was an automatic and we were able to pull the inspection plate...when I put the wrench on the first nut I was surprised that I could move the flywheel without loosening the nuts. Turns out that the flywheel was cracked and this was my problem. I later learned that those Ford 300's are bad about that. Give that a try...just might be your problem.
    That would be my guess too!!!!!!!!!!! Cracked Flexplate (flywheel) or loose crank to flexpalte bolts. (That is if it is an automatic trans.)

    Randy

  15. #15
    Member jmccloud's Avatar
    Join Date
    Feb 2003
    Location
    Maryland
    Posts
    694
    Corvette(s)
    1995 White Coupe LT-1 Auto
    Post Thanks / Like
    Rides
    0

    Default

    If it's a manual transmission, a worn pilot bearing can give some bad noises, often when the clutch is disengaged. Sounds just like a loose rod bearing.

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •