Engine Are Valves And Pistons Okay After Driver's Camshaft Skipped Several Teeth?

Discussion in 'SN95 4.6L Mustang Tech' started by cjcoburn, Aug 20, 2013.


  1. cjcoburn

    cjcoburn Member

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    So...if the driver's side timing chain tensioner is removed without locking the cam I learned that the cam will rotate and skip several teeth. Of course this all happened so quick I couldn't tell which way the cam rotated.

    My big worry now is are the valves and pistons okay. Of course the crankshaft wasn't in the safe position (keyway at 9 o'clock) when this happened, it was at about 7 o'clock.

    [​IMG]
    I read where one guy had this happen with his keyway at 4 o'clock and everything turned out okay.

    So is there a way I can check that the valves and pistons are okay (besides pulling the head)?

    I look forward to any help you guys can offer.
    Thanks!
     
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  2. Modular2v

    Modular2v Founding Member

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    you could run a compression test to make sure! This is why i always have mine in "lockout" while touching the cams.
     
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  3. Mattstang04

    Mattstang04 Active Member

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    What do you mean by "lock out"? I've never heard of this, just curious.
     
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  4. cjcoburn

    cjcoburn Member

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    I take "lock out" to mean get the crankshaft in a safe position (keyway on front of shaft at 9 o'clock?) and then lock the crank so it doesn't turn.

    As for my saga...I checked the piston positions and looked at where the cam lobes are at. All looks pretty safe except I'm not sure about #4. It's piston is pretty much at the top and its exhaust valve is working on closing.

    This pic is from the back of the engine looking at the passenger side cam shaft...exhaust lobe for #4. Do you think the cam has rotated enough to not cause a problem or really hard to tell?
    [​IMG]

    The plan is still to find a spring compression tool to remove the followers and do a leak-down test...and resynch cams and crank.
     
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  5. bhuff30

    bhuff30 Founding Member

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    From my understanding, you didn't rotate the crank, start the engine or otherwise move the crank. In that case, I wouldn't worry about it at all since the only force rotating the cam is the spring pressure. Just set the cam timing again and put her back together.
     
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  6. cjcoburn

    cjcoburn Member

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    Thank goodness the crank has not moved. I'll work on the not worrying. ;) I'll be good once it's running again.

    Thanks Brian.
     
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  7. Modular2v

    Modular2v Founding Member

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  8. Modular2v

    Modular2v Founding Member

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    that would be correct on lockout! Just a fail safe measure! Can never be too careful when it comes to possibly making an expensive mistake/accident! Also, judging by where the cam lobe is , i would assume you are ok! Also, its not like you were driving when it happened, the motor would have a **** ton of resistance if you are rotating it by hand if a valve was in contact with a piston and it would be enough for you to know!
     
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  9. cjcoburn

    cjcoburn Member

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    So this is how it all ended.

    I went ahead and got the valve sprint compressor tool from Advance Auto and pulled the cam followers out on both heads. This way I didn't have to sweat piston-to-valve interference while I was doing a leak-down (since the air pressure moved the pistons) or setting the camshaft-crankshaft timing. In fact, once I took the crankshaft position out of the equation setting the timing was real piece of cake.

    Now I have all new timing chain guides installed. Some of the threads on the right head where a guide bolt screwed in were mangled and came out, but a slightly longer bolt got me past that issue.

    As for the tool being worth the price, it sure made this so easy. I can also return it inside of 30 days for a full refund. Since the money is spent and it was such a great help I'm not sure if I'll return it yet. There's nothing like having the right tool for a job.

    Thanks everyone for sharing your thoughts and advice on this.
     
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    Last edited: Aug 25, 2013

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