On 22/07/2018 23:50, NY wrote:
"Brian Reay" wrote in message
news
You could use the handbrake partially, ie not full on.

Why use the handbrake at all, if the footbrake is still working fine?

Over reving the engine is the lesser of the evils compared to a high
speed collision.

I was thinking in terms of a con rod breaking which would probably seize
the crankshaft which would be bad news with the energy of the large mass
of the flywheel having to be dissipated very rapidly as it came to rest,
possibly locking the transmission (even with the slight clearance of a
clutch pedal being pressed) and hence the wheels.

I don't know how fast an engine might turn if all the mechanical load is
removed at full throttle, and how much extra load this would place on
the con rods. Modern cars with fuel injection and and ECU would almost
certainly have a rev limiter. But the car I was driving was much older
than that, with a carburettor, so there would be no limit to the engine
speed, other than normal engine friction and the maximum fuel flow that
the carb could manage.

Obviously it depends on the engine, but most overhead valve engines had
a sufficiently heavy valve train that valve bounce would seriously
interfere with beathing and limit revs. I am aware of a 1300 Ford Escort
where after a prang had the throttle jammed. It wouldn't restart. The
valves had touched the pistons and bent. No other damage and worked fine
after the valves were replaced.

An old Mini engine above certain revs would make a characteristic
clatter, above which there was literally no power and the engine would
simply sit there at around 5-6,000rpm.

As soon as ignition modules came onto the market they inherently would
incorporate a rev-limiter. There were some aftermarket rev limiters you
could add to the old contact style ignition system.