Eric Lund writes:
>First, I have been told that the life of an engine at redline under load
>(i.e. on the road and not on a test stand) is measured in minutes, say
>18-20 minutes at most.
Tell that to Showroom Stock racers, or (to keep on topic) MG vintage
racers. Granted, if you give it 16:1 compression and a 'one race' cam...
Now if you're talking about bringing a stock engine up to redline and letting
it _sit_ there for 20 minutes, you'll probably melt something due to
inability
of the parts to conduct enough heat away. But you'd probably boilover first.
>The argument was that the compression rings "bang around" and wear out.
>Can this be true?
I doubt it. Depends on the fit of the piston when warm. If you're
rebuilding
an engine, you can make this right. Cast and hypereutetic pistons 'grow'
less than forged pistons, but all can be designed to fit properly when hot.
The rings shouldn't 'bang around' at all. They should always ride on the
surface of the cylinder bore, otherwise they won't hold compression.
Most failure modes of over-revved engines is a thrown rod, and I can't see
how rings affect that. Usually it's overstressing the rod caps and bolts.
I'm sure Roger Garnett will correct me on this if I'm wrong.
>Second, I was recently told that using inferior grade (i.e. not this
>company's $8/qt stuff) motor oil will cause deposits to build up on the
>exhaust valves. I can understand how combustion products will deposit
>on the valves, but how in the world does the oil get there?
Don't really know, unless through bad rings or valve seals. But then
using a 'special' oil does not solve the problem, only the symptom.
Dave Williamson (silikal@aol.com) Spits in bits
All of this, of course, is IMHO.
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