noob valve spring question

Small Block Mopar Engine

  1. PRH

    PRH Well-Known Member

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    Final answer, or do you wanna phone a friend?
     
  2. yellow rose

    yellow rose Master Of Insanity

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    What part did I miss? Crossover is 180 degrees from TDC of the compression stroke.
     
  3. PRH

    PRH Well-Known Member

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    I think you need to phone a friend.

    On a SBM, with the timing set as in the pic...... where is the cam phased(in general terms)
    ...... and where is the piston?

    DD8CBDBC-AEF2-410C-B65F-533D83853E59.jpeg
     
  4. yellow rose

    yellow rose Master Of Insanity

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    What does that have to do with looking at valve opening at crossover?
     
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    • fishmens67

      fishmens67 Well-Known Member

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      With the crank gear installed as it's pictured. The zero mark on the crank gear installed at the 1 thirty position. puts the piston at TDC on #6 firing
       
    • PRH

      PRH Well-Known Member

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      Okay.....#6 firing.

      So where does that put the cam for #1?

      Let’s take it a step further........
      Assume that with the dots lined up like in the pic, the cam centerline is exactly where it’s supposed to be, which in this case we’ll say is at zero advance/retard.
      And, it’s a single pattern cam with symmetrical lobes.

      Where is the cam relative to number 1(and where is the piston)?
       
      Last edited: Aug 3, 2020
    • PRH

      PRH Well-Known Member

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      Everything actually...... especially as it pertains to that “180*” thing you were talking about.

      I figured the light bulb would have come on while you were 1/2 way through that bowl of rocky road you were eating while watching reruns of the twilight zone.
       
      Last edited: Aug 3, 2020
    • yellow rose

      yellow rose Master Of Insanity

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      Ok, for the OP to look and see if the cam is even close, he can take the valve cover off, and roll the engine over until the intake valve is opening and the exhaust valve is closing and line up the timing mark on the damper.

      Then look and see if they are open the same, or one is open more than the other and by how much.

      Doesn’t have shit to do with the timing chain or anything else.

      If he is on number 1 firing it’s 180 out from overlap. That’s why I said turn it 180.

      It ain’t hard.
       
    • yellow rose

      yellow rose Master Of Insanity

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      What I posted has nothing to do with the timing chain YOU posted.
       
    • PRH

      PRH Well-Known Member

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      If you took the time to think about what I asked in the post about the timing chain...... you’d realize how
      incorrect that statement is.

      The timing set in the pic is for a SBM...... so it should be relevant.
       
    • PRH

      PRH Well-Known Member

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      No one else wants to take a stab at post 31?
      It’s really easy.
       
    • RedB.

      RedB. Well-Known Member

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      180* ?
       
    • PRH

      PRH Well-Known Member

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      The pic of the timing set was supposed to be a visual aid to help turn the light bulb on.
      Particularly your reference to the 180*.
       
    • fishmens67

      fishmens67 Well-Known Member

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      dot to dot #1 is top dead center on the intake stroke
       
    • PRH

      PRH Well-Known Member

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      Yes...... and?

      Where on the intake stroke?

      What about where it is on the exhaust stroke?
       
    • RedB.

      RedB. Well-Known Member

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      I guess I am going to have to phone a friend . lol
       
    • yellow rose

      yellow rose Master Of Insanity

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      And what you are asking has zero to do with what I posted.

      You mentioned that he may be a couple teeth off and I offered what I think to be a very simple way to see how close or how far off he is.

      I said nothing about even removing the timing cover.
       
    • PRH

      PRH Well-Known Member

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      My apologies to YR for misinterpreting his “180*”.

      I read this as him saying the overlap was 180* from TDC.

      I know when I saw this, it sure seemed like he was saying, turn the crank 180*.

      The overlap isn’t at 180* from TDC, it occurrs while the piston is in the vicinity of TDC.

      So, The answer to my post 31 is...... if all those conditions are met(timing set dot to dot, single pattern cam, symmetrical lobes, installed with no advance/retard), the cam is exactly at split overlap at TDC.
      Both valves are open exactly the same amount(well..... actually, both lobes are at the same amount of lift).

      The pic of the T-set was to illustrate that when the dots are lined up correctly, the crank key is pointing towards the piston being at TDC(not 180* from TDC).

      One possible issue with trying to gauge the accuracy of the cam timing by looking at two valves on a hyd cam is....... you’re assuming both lifters are going to be bled down the same amount.

      If you do it based on only the centerline of the intake valve....... you’re not trying to compare it to another valve.
      It’s just where the one valve is relative to the mark on the damper.

      In theory, either method would answer the question about whether the cam was at least “close”...... or not.
       
      Last edited: Aug 4, 2020
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      • Keystone

        Keystone FABO Gold Member FABO Gold Member

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        Finally getting to updating this thread, over my lunch break no less. I used the suggestion of measuring the balancer and I marked a strip of masking tape based on the calculated distance of every 10 degrees. The first attempt was off by about 4 degrees, so I adjusted the spacing and it came out pretty close based on starting at 0 degrees and wrapping around in either direction to get to the 180 mark:
        1.png

        I didn’t have a dial indicator, so I bought one of those. I did what PRH recommended and found the peak lift at #1 intake to be right around 110 degrees. Since that looked correct, I then measured the opening/closing and lift as on cylinder #1 and compared it to the specs of the cam. I wasn’t getting numbers that matched, and the lift was significantly less than the specs. I realized what was happening was the lifters were compressing before the valve springs (at least I think that’s what was happening), so I removed the rocker shaft and measured directly at the pushrod:

        2.png


        This time everything measured close to the cam specs. Finally, I used a piston stop to verify the 0 mark on the balancer. I adjusted the screw until it got the crank to stop at exactly 10 degrees BTDC, then spinning backward it stopped right at the 10 degrees ATDC mark, which tells me the balancer hasn’t slipped.

        3.png

        4.png

        So unless I’m misunderstanding, the cam appears to be installed correctly. Thanks everyone for your help, but at this point I’m going put the valve covers back on and live with it for the time being. There are still a few more things to do to get the car roadworthy, so once that’s taken care of I’ll probably revisit this issue.
         
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