"harry" wrote in message
...
Am I right that the last thing you want to do is let the engine greatly
exceed its redline speed and risk it seizing up (I'm assuming that the
car
is old enough not to have a rev-limiter)?

What if it's an automatic?

The video that started all this showed the driver moving the selector lever
from D to N while doing "120 mph". I wonder whether any auto transmissions
allow the lever to be moved to N whe you are not stationary.

The speed of most engines is limited by the "valve bounce" or the engine
management system..
Theoretically, no damage should be caused.

As I said initially, this was a very old car (about 1975, IIRC) with no
rev-limiter or ECU. So valve-bounce and rate of fuel delivery from the
carburettor may have been the only limits on the engine speed under no load.

Maybe, for all the load noise that a no load engine makes at high revs, it
wouldn't seize up and maybe throw a piston out of the cylinder head or jam
the transmission even with the slight clearance between clutch pads and
flywheel when the clutch is down. I wasn't about to find out, and decided to
stop the whole engine rather than just disconnect it from the wheels.