[Healeys] To fit or not to fit

m.g.sharp at sympatico.ca m.g.sharp at sympatico.ca
Fri Apr 16 13:17:08 MDT 2021


Hi Ian,

 

Thanks for responding.  I am not going to another piston manufacturer; the
older AE pistons are excellent quality and have a good reputation.  You
can't judge the quality of castings and machining from an illustration, and
half the time what is illustrated is not exactly what is sold anyhow.  Omega
pistons are also excellent and I have fitted them to classic BSA and
Velocette motorcycles when I was doing a complete  balance, Carrillo rods,
bench flowing the head; the whole nine yards.  However, with the Healey,
unless you are building a performance engine, I do not see the need for
forged pistons.  That said, if I did not have the AE pistons, then I would
have gone with the Omegas.

 

I would still like to hear about the purpose/wisdom behind the change in
piston design that led to the introduction of the 5th ring.  They would not
have spent the extra money to switch up the machining if  there was not a
good reason.

 

 

From: Healeys <healeys-bounces at autox.team.net> On Behalf Of Ian Hey via
Healeys
Sent: April 16, 2021 2:09 PM
To: healeys at autox.team.net
Subject: [Healeys] To fit or not to fit

 

In a recent engine rebuild of a standard BJ7 engine which was fitted with
four ring pistons, when I looked at replacement pistons they were pictured
with five rings, which did not seem good to me.

 

I fitted Omega pistons from Denis Welch.  These have three rings with a
total width of 3.2mm compared with 9.8mm for the four rings.  (For the oil
rings only the width contacting the cylinder bore is measured)

 

Since friction is in proportion to ring width (possibly due to the lower
pressure required to make thinner rings seat against the cylinder wall) this
represents a reduction in losses to heat and a power increase (small).

 

Another, much more expensive, option for consideration.  I also have no
doubts about the quality of the pistons, whereas I am not sure about the
four or five ringed replacements.  They seem very cheap to me.

 

Ian

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