Piston/Valve CLASH ?

No. Both are DOHC engines. Toyota DOHCs are all noninterference.

Most Toyota SOHC are interference.

And the 1NZ-FXE used in the Prius has a timing chain not a belt.

According to Gates, the '97 Corolla has an non-interference engine, which means that the piston will not contact the valves if the timing belt slips or fails.

The Prius has a timing chain, and if it fails, the valves will probably contact the pistons.

If a timing belt "slips" does the value timing go out of adjustment (even if it does not strike the piston) or is it self-adjusting ?

Now that I think about it, the only way a Toyota timing belt would slip is if most or all of the cogs on the belt sheared off or the tensioner failed. If a timing belt did somehow slip, the valve timing will be incorrect and is not self adjusting.

The belt on my '86 Camry had only one or two of the cogs slough off the belt, and it was enough to strand the car in my driveway...and evidently it occurred upon starting ...or trying to start.

Doh! I stand corrected. I was thinking about the crankshaft side of the belt, but yes, since the camshaft sprocket is a much smaller diameter, the loss of one or two cogs would strand the car.

Mack gets the prize for catching Ray's error!