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Going for compression

Discussion in 'Motorcycle Tech Talk' started by voodoo1, Apr 6, 2007.

  1. voodoo1

    voodoo1 New Member

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    0k... heads coming off (02 wide glide)...a 40 dollar gasket kit later I am doing the labor heads a gonna get ported and polished my parents machine shop:cool:...am added benefit for me....now for the compression.. just enough to help bring to life a tad bit more, not going for anything other than this.. no boring.. etc... (leaving this one alone...(so to speak)
    so bumping the compression..... any strange or otherwise HD related clearances to look our for?
    I am doing this not to build a beast.but to allow this bike to breathe the way it should.... and the compression was an afterthought for something else to kickaround.. ..
    thnaks in adavance for the input... advice....:cool:
    voodoo1, Apr 6, 2007
    #1
  3. Clem

    Clem New Member

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    You will benefit by allowing the engine to breathe better - with pipes and free breather flow. The intake port is interesting... you can actually make it too smooth! Open it some but don't polish the port area since the flow will actually be impeded by the slick surface. Golfballing is the perfect surface for the intake. The exhaust is the one to open, polish and port match... Go with .030 head gaskets when you reassemble for a little more kick!

    Bill C.
    Clem, Apr 8, 2007
    #2
  4. voodoo1

    voodoo1 New Member

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    hey thanks

    pipes/carb/air all been done as usual.. I had discussed a bit of this b4 with a few others as well. over the years ..just now getting around to doing it to this bike. Never know when HD throws a little twist in the mix and I am sure other have done this already.
    voodoo1, Apr 8, 2007
    #3
  5. kenfuzed

    kenfuzed Administrator Staff Member

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    I'll second what Clem added. In fact you can almost ignore the intake port and spend your time on the exhaust port. On a Twin Cam the intake port is usually more than enough to handle most 88-95 inch builds. The exhaust port on the other hand is restictive and opening it up will greatly improve performance.

    I swear by the Cometic .030 head gaskets. If you had your heads shaved, decking, or installed high lift cams then you will need to check clearance. If you've never seen this, it involves placing clay on top of the pistons over the valve cutouts. Button down the top and hand crank the engine one turn. Then pull it apart and measure the thickness of the clay. However if you are staying relatively stock just check your deck height when first installing the cylinders.
    kenfuzed, Apr 8, 2007
    #4
  6. voodoo1

    voodoo1 New Member

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    thanks

    I got the technical side of the porting and polishing down( family owned machine shop). But ya can always get and idea or two b4 ya get into it.....thanks for the information....this won't be the first time I have done this..but the first time this bike will be that far taken apart..I am pretty happy about the fact I waited in this one since 2002 to really dig into it other than stage one stuff.. and working the carb some.
    any push rod issues?
    voodoo1, Apr 8, 2007
    #5
  7. ReeseSS

    ReeseSS New Member

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    Your cam profile, intake side, is what you should be looking at regarding compression ratio. You want your static compression psi to be around 170 to 180. If compression ratio 9.5 to 1 or less, the intake valve should close sooner to keep up cylinder pressure. (Timing about 36 to 38 degrees or less) and duration @ .053 under 240.(like 236-238 or less). If 10 to 1 or higher, then you will have too much cyclinder pressure and want to bleed it off by having the intake valve close later, which will also add more duration and moves your power band into a higher rpm range. So pick a cam that is going to work well with your compression ratio (or ratio to work with your cam) and you will have a performing engine!
    Last edited: Apr 9, 2007
    ReeseSS, Apr 9, 2007
    #6

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