Timing Chain

no belt or chain - just gears.

Not knowing much about belt vs. chain vs. gears, it would sound to me like the gears would be the best system to use. What then, is the advantage to switching to a belt or chain?

-Matt

The distance between the crank and the cams. On the pushrod engines there is only one cam and it's just above the crank, and since the crank gear is half the tooth count of the cam gear the two gears fit nicely there. On overhead cam engines it would be very impractical to have a train of gears running from the crank to the cams, so a belt or chain isused. Now in my opinion a well-specified chain drive system is preferred, but it's more expensive than belts so most makers use rubber belts to drive the cams.

Plus, using belts builds in a required maintenance cost that profits the maker to some extent.

JazzMan

I have had some OHC motorcycles that were gear driven. My BMW motorcycle, however, uses pushrods and is gear driven - just like the old subes. Gears are typically noisy. My 1990 BMW 325 is belt driven - however, it is the only car engine that BMW has ever made that is. The rest are exclusivley chain driven. Belts are likely to be cheaper and as was preciously stated keeps the service dept's in business.

NOISE! Chains are noisier than belts and gear drives are noisier yet. The other consideration is the rotational mass which puts wear on other components and reduces efficiency. TG

Didn't GM bypass the noise issue by using nylon gear teeth for a few years? Of course the nylon teeth eventually wore away and plugged up the oil screen and/or filter.

Don't know about GM. I do know that Ford use to use fiber teeth on a steel wheel gear on their 6 cylinders.. My father hated them because you could plan on it failing around 50-70,000 miles. I can remember helping him replace the timing gear in his pickups every 2-3 years.

It makes 105,000 miles very acceptable.

Jack y_p_w wrote: