The Sputhe 60º engine is quite a bit smoother than a 45º engine.  It is more powerful because of the duel intakes and a lighter, more rigid valve train.  It is also quite a bit stronger due to the wider 60-degree angle.  There is no need for piston-to-piston relieves and the bearings are much larger.

Harley-Davidson incorporated a number of the 60º’s features into its Twin Cam series engines.  The Sputhe Sixty has been running since 1992.  H-D uses the same crankcase venting system, the same scavenging system and the same type of lifters as the Sixty.

In the past, the Sixty has been tested in a number of configurations, single and duel carbureted, as well as fuel injected in displacements from 78 ci to 125 ci.  We built a 120 cid injected alcohol engine for Danny Grotto in Australia.  He has been drag racing the same engine for 11 years without failure.

*Not in production at this time.


Alloy Sportster

  • 80 cubic inches, 3.625” bore, 3.8125” stroke
  • 1978 to 1983
  • Duel carb aluminum heads & aluminum cylinders
  • First complete aftermarket V-twin engine
  • First street engine to exceed 100 horsepower


  • 104 cubic inches, 3.780” bore, 4.625” stroke
  • 1984 to 1998
  • First complete aftermarket engine V-twin offered
  • Biggest production engine made for many years
  • Many features were incorporated in the H-D TC88
  • First street engine to exceed 120 horsepower



  • 100 cubic inches
  • 3.780” bore, 4.500” stroke
  • 3.875” bore, 4.250” stroke
  • 4.000” bore, 4.000” stroke
  • 1991 to 1998
  • First 60 degree high cam aftermarket engine
  • First production dual carb Big Twin
  • First street engine to exceed 140 horsepower


E-Mail: sputhe@hotmail.com 

Tel: +1 (530) 268-0887 

PO BOX 2553

Grass Valley CA 95945

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