Rich,
I have similar pistons in my 1959 3000, which I installed back in the early
1970s. They produce a 10:1 compression ratio, which was great at the time
but means an octane additive with today's gasoline. One could obtain
pistons with the raised area slightly larger than the combustion chamber in
the head, and then file/machine the raised portion of the piston down so
that it's footprint matched the combustion chamber, less the necessary
clearances.
The theory was (maybe still is) that internal combustion engines are more
efficient at higher compression ratios, although my experience is that any
increased in fuel efficiency is quickly offset by the driver's right foot
once the added performance is discovered.
I suspect you are correct in that the camshaft is not standard. Again, back
in the early 1970s, the "thing to do" was to mate a 280 degree cam with the
pistons, which I did. Both are still in use today with no problems. I
think the only issue the current driver has is understanding the need for an
octane additive.
Ron
Subject: [Healeys] Healey 3000 Pistons
To: "Healeys" <healeys@autox.team.net>
Message-ID: <3A664277081842D59434830EE0F2CCB9@LIFEBOOK>
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Hello all,
I just removed the cylinder head from a tricarb 300 engine today and have
discovered pistons I've never seen before. The top of the pistons are flat
but
with a raised surface that takes a good portion of the combustion chamber
area. The sides of the raised portion are on about a 45 degree angle up to a
total height of almost 1/4". I can't imagine what the compression ratio must
be, but the P.O. had been working with modifying a set of manifolds from an
HD6 carb setup, and had modified the inlet manifold to bolt up Webers. So
obviously the P.O. was after some pretty wild mods.
Anybody heard of pistons like this? There are no markings on the crowns
except
a small circle about the size of a dime with numbers 1 thru 6 respectively.
I am trying to convince the present owner that we should bring things back
to
normal pistons and carefully check out the cam shaft for signs of
modifications that may not be "streetable".
Rich Chrysler
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