Hi again Ned,
In actual fact the BJ8 cam is quite an aggressive cam being the same grind
as was used in the 997 Mini Cooper. Only because it is in a big six does it
not exhibit the loping idle of the Cooper.
I have to disagree with the idea of going for longer duration or more lift
in a BJ8. This is a case of more is not necessarily better. The lift and
timing of a cam are always compromises and I would suggest that the BMC
engineers arrived at the BJ8 profile after many hours of dyno tests on many
different designs.
In my experience, more with 100S engines than sixes, adding more duration
and lift without increasing valve sizes only serves to degrade the low end
power and move the maximum power up the RPM range. Neither 100 nor six
cylinder Healey engines were designed to rev, in fact the bore to stroke
ratio is such that when 3000 ft/min maximum piston speed is reached the
power drop off is dramatic.
The fact is that no amount of twiddling can defeat the laws of physics. If
the piston accelerates down the bore faster than what is required to reach
3000 ft/min the air simply cannot keep up and no more charge is ingested.
(Unless you opt to fit a blower)
I also contend that most of us spend most of our Healey driving time under
3000 RPM so unless you intend to try to get the last ounce of power from
your BJ8 and drive around and between 4 - 6000 RPM leave well alone.
Just my opinion but based on a little experience.
Michael Salter
www.precisionsportscar.com
-----Original Message-----
From: owner-healeys@autox.team.net [mailto:owner-healeys@autox.team.net] On
Behalf Of Ned Smith
Sent: Wednesday, May 03, 2006 12:56 PM
To: Austin-Healey List
Subject: New Camshaft Profile
I have gotten advice from several people on and off this list to put a "high
lift" profile on my reground cam shaft. They sight increased HP and a
"better sports car feel". These sound like desirable additions but at what
cost? What is the down side?
I will do mostly local daily driving with occasional trips on the
Interstate.
What do you think?
TIA
Ned Smith
BJ8
near Chattanooga, TN
N34.98 W85.5
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