Straight -cut or Cross-cut Cam Gears

17th may 2008

The debate between strait-cut gears and regular cross-cut gears has been ongoing for some years and is something that many engine builders will come up against and will have to make and educated guess based on the information that is available to them.

Certainly the pros of the straight cut system are the increase in performance that the straight cut gears low friction give. The Cross cut gears however seem to have a much stronger build quality usually made from aircraft gauge billet Aluminium or Magnesium where as the straight cut gears are noticeably thinner and made from steel or use a steel gear and alloy drive gear. I originally elected for the Cross-cut gear system as I was also aware that the straight cuts system gave the engine an odd wine as the gears spun together.

The two featured camshafts are on the straight cut gear above left an Engle FK8 and on the crosscut to the lower right a Bugpack high lift cam.

The use of this lightweight and narrowed straight cut cam and crank gear set will virtually eliminate all cam bearing thrust wear created by high lift cams and high pressure springs. Straight cut gears are also available in an adjustable type witch allows fine tuning of the valve timing from the cam. A typical engine built with a straight cut cam can be heard here: http://www.youtube.com/watch?v=SynhO3LoJsA. The wine is very noticble and can be mistaken as the sound of a supercharger.

The Cross-cut gear type apparently wears better and is now also available in adjustable models and also some with steel and alloy mixed gearing sets.

Personally I am going to fit the Straight cut gears and see how they fair in my new engine. I will write in another blog on how to set up the cam with the correct the adjustments when I get to the pre-build make up.