In reality the maximum RPM of any engine is limited by the load on the rod
bearings. A 3000 cylinder engine has a stroke to bore ratio of 1.066 but the
reciprocating assembly is pretty heavy. The engine only has 4 main bearings
so I reality trying to obtain a sustained RPM on excess of 5500 is indeed
going to require the injection of some very expensive bits.
I'm sure there are people out there who have managed to build engines which
will pull 6500 reliably but in my experience the torque starts to drop off
very quickly after 5000 and trying to pull more is very much a case of
diminishing returns.
In addition to this you are approaching 3500 ft/min mean piston speed at
6000 RPM and after that you are definitely going to need some much thinner
rings than 0.145".
As people have said before the strength of both the 4 and 6 cylinder Austin
engines is in their torque and that is, after all, what moves you.
Michael Salter
www.precisionsportscar.com
-----Original Message-----
From: owner-healeys@autox.team.net [mailto:owner-healeys@autox.team.net] On
Behalf Of Richard Hosmer
Sent: Sunday, November 05, 2006 6:32 PM
To: PG; healeys@autox.team.net
Subject: Re: Sunday Funny, was Re:Crank and Rods (bluenoses hit "Delete")
IIRC, the last time I got my crank wedged, I had taken everything off! :-)
But more seriously, if I may ask, where, and in what gear, do you see
yourself turning 6500 RPM, on the "street"? In 1st, it is just vehicle
abuse, and in 2nd, it would be illegal. If you are going to the drag strip,
that probably isn't the most efficient point to shift, anyhow.
Hollywood Sports Cars campaigned an extremely capable, and very durable,
3000 in the mid-sixties, which used the stock rods and crank, but they had
been VERY VERY carefully balanced and polished, so, it IS possible.
Dick Hosmer
|