interference or non-interference

[Danglerb]

Timing chain that goes 6 inches on a push rod motor isn't the same issue as with an overhead cam motor.

If I was a mechanic I think I might say everybody use a small block chevy, but as an enthusiast I prefer to leave everything on the table for the designer to pick and choose from.

With the 928 its kind of moot, we have the motor we have, and I don't expect to ever see a timing chain on a 928 block. I do expect to see continued improvement in the weak links of what we do have, and maybe that will be sufficient.

[Normy]

Smokey Yunick talks about timing chains in his book about engines. He says that he investigated timing chains on chevrolet small-block V8's by putting a transparent cover over the chain, and he says that at higher RPM's you couldn't see the thing because it was vibrating so much! His Indy chevrolet engine used a pickup-truck gear drive for the cam.

Ford took apart a Porsche M28 V8 engine before they designed their "Romeo" or "Trident" series of engines. There is nothing new under the sun, and they already knew the limitations of the timing belt, since they had experience with their EXTREMELY rare SOHC 7.0 liter engines from the late 1960's. They used a chain on those motors, and they use them now on all their new big engines, even up to the 6.8 liter V10 for the trucks.

Belt drives can loose teeth and slip, and need to be changed [on 928's] at the 45k mile interval. Chains can start to stretch after 150k miles.

N!