Planned mix 'n max Airhead engine build (1969-1979)

Discussion in 'Airheads' started by StephenB, Oct 18, 2010.

  1. StephenB

    StephenB G(/)S ... what else!

    Joined:
    Aug 24, 2005
    Oddometer:
    2,045
    Location:
    Ontario
    What problems of mechanical/fitment nature will I be facing when I assemble these parts to an engine:
    • /5 stock engine case (03/72 SWB R60/5)
    • /5 stock crankshaft
    • 336 "sport" cam for airheads from 1979 on (key'ed for bean can and square drive (flats) to inner oil pump rotor side)
    • single row timing chain
    • 1979-1980 timing cover with hydraulic chain tensioner
    • points in beancan
    • 107mm alternator
    • /5 engine cover (or any other for that matter)
    • 750 (or 900cc) barrels, pistons and heads
    The 336 "sport" cam (asymmetric 38-46-58-26) was originally designed to work with the 750cc engine in racing applications. It was retroactively approved for all engines with 40mm exhaust valves (R90/6, R90S, R100/7). Has anybody first hand experience with using it in a 750 or 900cc engine? What if I added the thinner base gasket to raise compression by about 1/2 a point?

    I want the bike to be an everyday rider with the extra power available when it is needed or desired. The mods should not affect gas mileage or reliability ... if possible. Am I asking too much?

    Stephen
    #1
  2. bgoodsoil

    bgoodsoil Dare to be Stupid

    Joined:
    Jul 9, 2008
    Oddometer:
    4,673
    Location:
    Washington, DC, USA
    no idea! :lurk
    #2
  3. Stagehand

    Stagehand Imperfectionist

    Joined:
    Oct 6, 2004
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    31,514
    Location:
    Shawangunks
    me neither, but :lurk
    #3
  4. pommie john

    pommie john Long timer

    Joined:
    Apr 9, 2008
    Oddometer:
    1,571
    Location:
    Brisvegas, Australia
    I run a 336 cam in my racer engine. Not having had any experience with any other cams in there, I can't say how different it is. It does produce good power with the max torque at around 4500-5000RPM, max power at 7000ish.

    I have heard that you have to check valve to valve clearance with certain big valves, but I'm not sure how big the valves have to be before they clash.

    The rest of what you suggest seems good as far as I know.

    I have a /5 case, post '81 clutch/flywheel, later cam and bean can ( with Boyer installed). Make sure you use late model cam followers, ( not the ones with spiral cut outs) and the later rockers are supposed to be better.
    #4
  5. Caddy82rats

    Caddy82rats Long timer

    Joined:
    Mar 8, 2007
    Oddometer:
    1,243
    Location:
    South France
    that sound interesting
    Timing case 79/80 means no gears for mecanical tach
    #5