There's basically no axial thrust on the bearings because of the straight cut design, whereas helical type gears tend to force eachother axially because of the screw action made from their spiral shape. Straight cut gears (Spur type) have a smaller tooth contact area, (One tooth in contact at a time) thus reducing the area which takes the load. Because of this there is a clicking sound made at low speeds, but because the cam and crank are rotating relatively fast this is heard as a whirring sound. Helical gears spread the load over a larger area and over at least two teeth at a time, which means the rotation is smoother. Gearboxes commonly use spur type for first and reverse, and helical for the rest. You may be thinking spur type are weaker, but they are usually made stronger in the first place. All this means you would have a strong gear which causes less wear to the bearings, giving better performance.
And that's the way the cookie crumbles.
-Staggers.
STAGGERS AUTOMOTIVE - Heavy Vehicle Diesel Specialist
JB CUSTOMS & CLASSICS - Car Builders
2/53 Tradelink Drive, Browns Plains
