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Thread: Cam thrust button

  1. #1
    Heatseeker
    I'm done degreeing the cam and I'm setting up to check cam end play. I go to install the cast aluminum timing cover(which was machined in the button area previously) and it won't sit flush to the block. The cam thrust button is too tall. Like an 1/8". Using a straight edge, it appears that the srockets are in properly aligned. What should I do? Machine the button down?
    The timing set is a Manley that came with the Torrington bearing behind the cam sprocket and the front thrust bearing.
    Help!

  2. #2
    Blown 472
    Maybe the rear freeze plug is in too deep??? and pushing the cam forward?? hell I dont know I work on ferds.

  3. #3
    Heatseeker
    472, I haven't put the plug into the back of the block yet. I was going to put the indicator on that end of the cam to check the end play and then install the plug.
    Thanks though.

  4. #4
    Fiat48
    If the cam and crank sprocket are aligned, then evidently this type of chain setup doesn't require machining the block to accomodate the thrust washer. If that is the case, then machine the thrust button down. I do know there is more than one length of thrust button available, long and short.
    On another note: A racer has just contacted me and said his Cloyes timing chain is actually broken, the motor destroyed. Never heard of such a situation. I'll go look at whats left of the motor tonight and try to determine the cause.

  5. #5
    Infomaniac
    The rod came up and stopped the cam. Broke the timing set.

  6. #6
    Heatseeker
    Looking at the original timing cover on the old engine, I noticed that the cover has a bubble in it, at the center of the cam sprocket. This cast cover I'm using is flat. I think I've figured out how much to machine off of the button. I'm going to make a dummy first, so I don't cut the original down too far.
    Thanks for the replies, I'll let you know how it turns out.

  7. #7
    Fiat48
    Infomaniac:
    The rod came up and stopped the cam. Broke the timing set. Pretty accurate diagnosis from 2000 miles away. Next time I won't give you so much "Infomation". Looks like #5 and or #6 rod bearing spun, rod broke, so much damage it's hard to tell what went first. But it's obvious the chain breaking was after the fact. I have no rod breaking experience as we all know I change them one run before they break.
    [ April 14, 2003, 11:07 PM: Message edited by: Fiat48 ]

  8. #8
    wfodude
    Hey john...Fiat is correct there are 2 different length buttons in a needle thrust assy. I had to machine mine down to fit also. It was no problem and still works perfectly.You can also get the solid aluminum button and machining them is simple.Put the gasket and cover on it and measure how far open it is with a feeler gauge then cut appropriately.you have to be careful to keep it even and square. take little cuts and check it several times as you go. You can do it in your garage with simple tools ...a lathe makes it much easier.

  9. #9
    Blown 472
    I was just reading about this last night in my Smokey Yunick book, he makes up some deal on the back of the water pump to push agianst the timming cover, said something like .002 to .006"
    clearance tween the cam and the cover, when the cam moves around it throws the timming all over the place.

  10. #10
    Heatseeker
    WFO, Figures I got the long button assy! Just my dumb luck. I kind of figured I didn't have a choice but to machine it down. I just made a dummy to get an accurate reading. That way I don't trash the supplied piece. I'm getting .020" with the dummy.
    Blown, I know why Smokey reienforces the cover. I have a cast aluminum cover and I can get .003" deflection by just leaning on the back end of the cam.
    What do you guys set the end play at?

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