My suggestion is to pay attention what Jon Wood is offering on cam
followers. Particularly the diameter is of utmost importance when
installing big cams. Don't forget the easy warm up and DO NO BLIP THE
THROTTLE WITH A NEW CAM UNTIL THE ENGINE HAS RUN FOR TEN OR FIFTEEN MINUTES
TO SOMEWHAT WORK HARDEN THE LOBES. It hard to wait to hear that nice sound
but you can do terrible damage in just a couple minutes by not being a
little patient.
----- Original Message -----
From: "A.J. & C. Wood" <wood@dandrade.freeserve.co.uk>
To: <fot@autox.team.net>
Sent: Wednesday, September 04, 2002 5:25 PM
Subject: Cams & followers
> May I add a few thoughts?
> 1. Nearly all modded TR engines have excessively heavy valve springs
fitted.
> Some you could use as road springs. Remember most engines are only going
to
> around 6500rpm, not the 9000rpm these springs will cope with. (OK - it's
> diffferent for 1300 Spitfires). In a TR-4, you will marvel at the way your
> skew gear disappears as the camshaft bends under load, especially if you
are
> unlucky enough to have one of those uprated alloy oil pumps on board. The
> 6-cylinder just sheds its lobes, not helped by certain cam profiles which
lift
> too fast for a 0.8"follower and run off the side of it... We see engines
where
> the valve cotters are belting the tops of the valve guides, and guess
what,
> the cam people get the blame again for a failure.
> 2. We now grind cams on chillcast iron blanks, and for some years have
used a
> modified Hillman Avenger follower, both on original hardenable and
chillcast
> cams. Diameter is as original, material is also chillcast.
> Sorry, don't know the hardness, but I'll find out.The diameter really
should
> be as large as possible in order to use fast accelerating profiles. I use
a
> large follower in the TR-6 race engines for this reason - it's not too
hard to
> bore out the block to suit. I have also had a large batch of OE TR-6
followers
> made and nitrided, but NOT shortened or mucked about with. These go nicely
> with any cam.
> 3. A loose crank grind gives more oil throw-off onto cam & followers -
it's
> their only source of lubrication.
> 4. Follow break-in procedure rigorously and don't ever use thin oil.
>
> Returning to my first point: the greatest proportion of failures I have
seen
> has been due to overspringing.
> You should be able to turn a freshly built motor, plugs out, with no more
than
> 30ft lb. on the crank nose. That's my rule of thumb, and I'm sticking to
it.
> Jon Wood
> The British Lobe Office
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