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Thread: Valve Adjustment and Being 'On The Rock'

  1. #1
    Member kings1527's Avatar
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    Valve Adjustment and Being 'On The Rock'

    So I'm adjusting my valves right now and I took a wrong turn somewhere on something pretty simple. As the manual says, you want to move either number 5 or number one 'on the rock'. If I'm 'on the rock', then neither the intake or exhaust arms of that particular cylinder should move, correct?

    Here's what I have right now:

    -number 5 inlet = doesn't move (spring is compressed in relation to the other inlet valves)
    -number 5 exhaust = moves

    -number 1 inlet = moves
    -number 1 exhaust = doesn't move (spring is compressed slightly in relation to the other exhaust valves)

    If I move everything one full rotation, it basically reverses itself. I'm trying to get set up on the rock to where neither number 5 or number one arms will move but I'm not sure where to go with this. My question is this:

    1) Given my positions above, which is on the rock? Number 5 or number 1?

    2) If I'm on the rock, what can I see visually if I'm looking inside? Will the springs be compressed or extended? If I can visually see something with the springs under the adjustment screw, then that will tell me which one is on the rock and where to start adjusting.

    Thanks!
    Alex Abdalla
    6575

    Late '81, 5-speed/gray interior with 47k miles

    On a mission to make my car look concours with completely updated and reliable internals. My blog is located at www.delorean6575revisited.blogspot.com

  2. #2
    Uncensored Hypocrite stevedmc's Avatar
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    Hopefully this video helps answer your questions. Its been a while since I've done a valve job but if you still need advice after watching the video please let me know.

    Rest assured, we have a backup of Farrar's car blog and it will be restored in the near future. (Steve Rice - March 2016)
    Rest assured, we have a backup of Shep's posts and all of them will be restored in the near future. (Steve Rice - March 2017)

  3. #3
    Member kings1527's Avatar
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    Thanks Steve. I guess it turned out that I didn't go forward enough to put them both on the rock. Easy solution. I was under the impression that if you move the crankshaft pulley to the '0' marker on the plate cover, that'd automatically put both the intake and exhaust on the rock but obviously it doesn't work that way.

    Moral of the lesson: move the crankshaft pulley into position on the plate and each time you come up on '0' on the timing cover, check the intake and exhaust on either 1 or 5 and stop when both the intake and exhaust are on the rock. It might take a couple revolutions to get you there. I never knew that.
    Alex Abdalla
    6575

    Late '81, 5-speed/gray interior with 47k miles

    On a mission to make my car look concours with completely updated and reliable internals. My blog is located at www.delorean6575revisited.blogspot.com

  4. #4
    Uncensored Hypocrite stevedmc's Avatar
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    Awesome. The job can be a little confusing the first time but it is super easy. Checking to make sure the correct valves are "on the rock" is what lets you know things are being done the right way.
    Rest assured, we have a backup of Farrar's car blog and it will be restored in the near future. (Steve Rice - March 2016)
    Rest assured, we have a backup of Shep's posts and all of them will be restored in the near future. (Steve Rice - March 2017)

  5. #5
    I never understood what "on the rock" meant so I never bothered adjusting my valves.

  6. #6
    Uncensored Hypocrite stevedmc's Avatar
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    "On the rock" is just a fancy term meaning both your intake and exhaust vales are shut. When they are shut you can't slide your feeler gauge in there, hence the term "on the rock".
    Rest assured, we have a backup of Farrar's car blog and it will be restored in the near future. (Steve Rice - March 2016)
    Rest assured, we have a backup of Shep's posts and all of them will be restored in the near future. (Steve Rice - March 2017)

  7. #7
    Devout Follower Of He Who Walks Behind The Rows NightFlyer's Avatar
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    Quote Originally Posted by Farrar View Post
    I never understood what "on the rock" meant so I never bothered adjusting my valves.
    Remember when I suggested that a back pressure problem with your exhaust may have caused your engine to die and you responded that you noticed that the exhaust was stinging your nose? It's also possible that you have an exhaust valve stuck open or some other problem with the valve-train.

    Did you do that compression check yet?
    "Driving Concours - proving it's possible with every mile!"

    --Josh S.
    #1798

  8. #8
    No, I haven't done anything. I did open the garage the other day to make sure the car was still there...

    Thanks for the info! Now I can understand a little more of the Workshop Manual...

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    Quote Originally Posted by stevedmc View Post
    "on the rock" is just a fancy term meaning both your intake and exhaust vales are shut. when they are shut you can't slide your feeler gauge in there, hence the term "on the rock".
    oops

  10. #10
    I think Steve means at least partially open. He is correct that you can't slide a feeler gauge between the rocker arm/valve stem.

    Makes one nostalgic for hydraulic lifters....

    Bill Robertson
    #5939

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