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Valve/Cam timing Petrol 2.25- am I over thinking this??

Discussion in 'Series Land Rovers' started by MFC, Apr 10, 2021.

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  1. MFC

    MFC Active Member

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    Timing 2.25.jpg Hi All,
    Currently rebuilding my 2a and the engine after a 40thou rebore. All going well and have put the cam in ok. Setting up the valve timing as per book (both green and haynes) lined up the cam sprocket with the P on key and the other P to the bolt hole all ok. AndI have the crank at TDC (keyway up) first by eye and then by dti, and all is as it should be.
    My understanding is that TDC is on the compression stroke, right? well if that is the case why is inlet valve 2 open when lined up with the P?????. It looks like it is to my thinking 180 deg out or have I made a school boy error here - a bit confused. Any thoughts??
    Cheers
     
    Last edited: Apr 10, 2021
  2. MFC

    MFC Active Member

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    A Few other pics of where we are aim to be on the road end of April
     

    Attached Files:

  3. jamesmartin

    jamesmartin Well-Known Member

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    yes your 180 degrees out
     
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  4. MFC

    MFC Active Member

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    Thanks James, any idea how that is possible?
     
  5. jamesmartin

    jamesmartin Well-Known Member

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    turn the cam one rotation
     
  6. MFC

    MFC Active Member

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    Cheers james but if I turn it 360 deg I end up back where I started or am I missing something?
     
  7. jamesmartin

    jamesmartin Well-Known Member

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    have you got the chain on, if you have p aligned with the correct hole in engine block both valve lobes on no1 should be pointing down
     
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  8. MFC

    MFC Active Member

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    not yet wanted to be sure of the timing first
     
  9. MFC

    MFC Active Member

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    Quick up date - after looking at the picture I posted it looks like, due to the angle of the engine stand I was aligning with the wrong hole on the timing case. Now it seems that when aligned with the top hole, the cam is on the overlap between exhaust and inlet - is this ok?? still seems odd to me
     
  10. TheMegaMan

    TheMegaMan Well-Known Member

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    I've discussed angular definitions with @jamesmartin here, before! :D

    If the cam is 180 degrees out, I think you want to rotate the crankshaft by one turn. 360 degrees on the crank will give you 180 degrees on the camshaft. That's what you need, isn't it?

    And you probably don't want to go turning the crank when the timing chain is off. Best part it at 90 degrees off TDC (so the pistons are all at half stroke), and then you can rotate the camshaft to suit, without having to worry about the pistons hitting the valves. If you're moving the crankshaft, you really need to be sure the camshaft is synchronised so the valves are shut enough when the pistons reach the top of their stroke,.
     
  11. TheMegaMan

    TheMegaMan Well-Known Member

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    It does sound like you're at the end of the exhaust stroke, not the compression stroke.
     
  12. MFC

    MFC Active Member

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    I agree, not sure how to proceed as both valves should be closed in compression and I have it set up as per book, can't be the crank in wrong position as chain not on!
     
  13. jamesmartin

    jamesmartin Well-Known Member

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    you want no1 valve lobes pointing down no4 both pointing up
     
  14. MFC

    MFC Active Member

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    thanks James will have a look tomorrow and see if I can make sense of this. Wonder whether the camshaft sprocket could be a replacement (from another engine) or something like that but I think most cams were the same in the series world at that time.
     
  15. TheMegaMan

    TheMegaMan Well-Known Member

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    If you need to realign the camshaft and the chain is off, you probably want to back the crankshaft up by 90 degrees, and then it will be safe to rotate the camshaft into the correct position. Lock it in place, and then turn the crank back up to TDC. But you need to be really sure the valves are in a 'safe' position before letting the pistons back up to the top again.
     
  16. jamesmartin

    jamesmartin Well-Known Member

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    cam key to inner p then outer p to outer most top hole
     
  17. MFC

    MFC Active Member

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    Ok thanks but at the moment the head is off as is the chain do we should be safe here
     
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  18. MFC

    MFC Active Member

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    Think I have that but 'outer most' is the same as 'top'??
     
  19. jamesmartin

    jamesmartin Well-Known Member

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    top one on left in pic
    [​IMG]
     
  20. MFC

    MFC Active Member

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    Thanks James, Pretty sure that is where I have it but will review tomorrow with fresh eyes and hope I can see the school boy error
     
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