Broken cam shaft bolt

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by dutra, Jun 8, 2017.

  1. dutra

    dutra Member

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    I have mounted a Piooneer front mag drive. After a few runs, we broke the bolt and dowelpin to the cam shaft. What happened to the engine, I do not need to tell. Now I put the engine together with new parts and would like to have some advice how to avoid it happening again.
     
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  2. kosky racing

    kosky racing Comp Eliminator

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    Do you have the special bolts for the cam. Some cams need special shouldered bolts-if you dont use them they break like you described
     
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  3. dutra

    dutra Member

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    Where can I find these bolts
     
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  4. Mike Canter

    Mike Canter Top Dragster

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    How dowel pins do you have? If only one then you should consider modifying it for two
     
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  5. kosky racing

    kosky racing Comp Eliminator

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    ARP
     
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  6. Nitro Madness

    Nitro Madness Super Comp

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    I know this goes without saying....red locktite on the cam drive bolts....into the cam and the 11 bolt vernier timing hub if you have that style...the high frequency engine vibration will loosen bolts you never thought would ever come loose...
     
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  7. aj481x

    aj481x Member

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    If ordering new parts, get the 6 bolt setup.
     
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  8. Unlimitedaero

    Unlimitedaero Member

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    The dowel pin is simply a locator for valve timing. The critical issue here is the clamping force between the the gear and the shaft. However, you do it with more bolts or if you don't have options because of gear availability etc, use the highest tensile strength bolt with the most thread engagement and torque to the spec that is recommended for that bolt. Also, as Mr Kosky mentioned, use a bolt with a shoulder to provide a smooth surface for the gear and pay attention to the radius under the head of the bolt and it's contact with the gear.
     
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  9. mcmahonc

    mcmahonc New Member

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    I use 12pt shoulder bolts in mine. Then use AN washers so the shoulder is the correct length to engage the distributor / pump drive and cam gear. Cut off excess threads at ~ 2x dia. Fill the dowel hole in the cam so the dowel also correctly engages the distributor / pump drive and cam gear. My dowel would go through the cam and into the oil pan. I also had a problem with the center / shoulder length of the distributor / pump drive. It centers in the cam gear but it was too long for the thickness of the cam gear and the bolts did not clamp it correctly. Grind it down as needed. Once set up, it will work fine.
     
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  10. dutra

    dutra Member

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    Thank you for all input. Now I've checked all parts and it's like mcmahonc says the mag / pump drive is too long for the thickness of the cam gear. Stupid of me not to check it from the beginning.
     
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