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Thread: This Can Not Happen

  1. #31
    Gilbert Pierce's Avatar
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    Default Re: This Can Not Happen

    Be careful about radiusing the valve end of the rocker arm. That radius must be absolutely parallel to the rocker arm bore centerline. If not you will have too small a contact area on the toe of the arm, high contact loading and spalling on the contact surface,toe, of the arm.
    I had an oil filter full of steel chips because a rebuilder didn’t check the calibration on his rocker arm resurfacing jig.

  2. #32
    mmoyle's Avatar
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    Default Re: This Can Not Happen

    Quote Originally Posted by Gilbert Pierce View Post
    Be careful about radiusing the valve end of the rocker arm. That radius must be absolutely parallel to the rocker arm bore centerline. If not you will have too small a contact area on the toe of the arm, high contact loading and spalling on the contact surface,toe, of the arm.
    I had an oil filter full of steel chips because a rebuilder didn’t check the calibration on his rocker arm resurfacing jig.
    Thanks... I don’t have the tooling to do the rocker arms..



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  3. #33
    mmoyle's Avatar
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    Default Re: This Can Not Happen

    Quote Originally Posted by KSG View Post
    Are the tips of the valves heat treated or other to reduce wear. Many are and should not be ground. The angle of the rocker arms are as important as the valve clearance. Proper ratio can be affected and valve side loads can increase dramatically. Valve pressures are low on lycomings so they are more forgiving of less than ideal valve train geometry than a race engine but wear will increase on valves and guides.
    I’m pretty sure the exhaust valves are sodium filled....and if I remember correctly, sodium filled valves can not be heat treated. There isn’t any indication of stellite facing on either the seat area of the exhaust valve or tip. Monday I’ll give Alaska Aircraft cylinders service a call and pick someone’s brain.. as my comfort level on these cylinders isn’t good. I did identify the seat type...they’re flat not the Allison type Lycoming uses.. if they were Allison...all of the exhaust seats would probably need to be replaced...especially cylinder number three...It took a good amount of grinding to remove the 60 degree angle cut. Maybe by the age of ninety I might know enough about all this stuff...until then....this is the best place to put it out there for advice and constructive criticism...
    Thank you all.


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  4. #34
    mmoyle's Avatar
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    Default Re: This Can Not Happen

    Quote Originally Posted by Steve Pierce View Post
    No idea. I usually compare them in length and start with the shortest one and start installing and checking dry tappet clearance. Would be kind of a pain to remove a cylinder, grind a valve tip and reinstall and check. Order the right parts. Won't matter a month or a year from now. You do have the rotator cup installed?
    Steve,
    Yup rotator cups all there. I agree...the right parts sure to make it easier... and now that I’ve found the length by part number can figure out which push tubes we’ll need to order...by clamping a dial indicator to the cylinder...somehow...then measure the valve lash..


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  5. #35
    mmoyle's Avatar
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    Default This Can Not Happen

    Spoke with Tyler at Alaska Aircraft Aircraft Cylinders today. Ordered 4 each dash 10 and 4 each dash 11’s. Discovered even the tubes with the same part number can vary over 0.032” in length.
    Spoke about the valve stem height and different tricks to obtain the proper valve lash.. what I didn’t know...the rocker arms can also be ground to obtain the proper valve lash. The valve stem height can adjusted...that the sodium filled valves from Superior do not have stallite any where on them..and the valve stem is NOT heat treated..so...can shorten if needed. Also discussed the amount of material I removed to undo an improper valve seat grind. Even though the 30 degree angle on the exhaust seat is near to the outer edge of the seat..I’m still oh Potassium.


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    Last edited by mmoyle; 06-25-2018 at 06:51 PM.

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