grinding rocker boxes for .575 lift cam

Discussion in 'Harley Davidson Extreme Modification' started by B-1B_Guy, Feb 13, 2010.

  1. B-1B_Guy

    B-1B_Guy Junior Member

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    Does anyone out there have pictures of properly ground rocker boxes for a high lift cam? Bike is an 09 Ultra Classic and I'm in the process of installing stage 3 heads and a 575 lift cam. I know I need to clearance the valve spring but am not sure how much to take off. Any help would be appreciated.

    thanks.
     
  2. glider

    glider Veteran Member

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  3. Chopper

    Chopper Senior Member

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    I always clay the rocker boxes just like the pistons for the heads, I go a little bit at a time untill I have the clearance I need, then I give it a touch extra, nothing worse then hearing a tapping come to life after the engine has fully warmed up.
     
  4. B-1B_Guy

    B-1B_Guy Junior Member

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    Thanks guys. I did do a search but came up empty. I'll put the rockers on and adjust the pushrods, turn it over by hand and see what happens. Appreciate the help.
     
  5. Chopper

    Chopper Senior Member

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    When claying I give a minimum of .060 for heat expansion for boxes, paying attention to upper spring collars on side walls and top box at rib suports above rockers. I found plastilene from craft stores works for me and does not get hard while stored. Lot of my friends like using a piece solder for piston/valve clearance.
     
  6. prodrag1320

    prodrag1320 Account Removed

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    clay is fine for cleancing rocker boxes,but we`ve seen guys actully bend valve by using clay or solder checking valve to piston.the way we do it is to take the springs off,get your TDC lift and mark the valve stem off the top of the guide with your TDC lift + .060,then with the valve on the seat,open the valve to the mark,no contact,good to go.contact,measure how far you are from the mark,and thats the clearace you need to cut piston or sink valve (ide cut valve pockets)
     
  7. Chopper

    Chopper Senior Member

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    Prodrag that's a great tip, been a while since I've done any real engine work. the way I mark stuff and measure I'd probably screw it up but sounds simple, it's a great way around the clay or solder, if you ever get a chance to put a photo thing together with that, It would make a great post. Is .060 enough clearance now a days, I think I always use to give it ,080 valve/piston?
     
  8. prodrag1320

    prodrag1320 Account Removed

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    with right springs,.030`s ok(but ide stick with .060).on the previos post,we use dykem on the stem,use a dial caliper,open it up to the TDC lift,and just make a little mark in the dykem off the top of the guide,real easy
     
  9. chuckyd1

    chuckyd1 Member

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    I've found that it is the rockers that contacts the valve cover, not the valve springs.(spring height should be the same regardless of what cam you have,as the lift goes down on the valve side)
    I put fingernail polish on the top of the rockers at both ends, and dropped the valve cover on. I ground some metal off the inside of the cover where the nail polish had been transferred. I continued this until none appeared, then took off about .060 more. After that I did it one more time, but this time torqued down the valve cover, and with the plugs out, carefully rotated the engine using the rear wheel with the trans in 1st gear. (STOP IF ANYTHING BINDS!!) If there is no more nail polsh transferred, you should be good to go.