[Healeys] Healeys Digest, Vol 14, Issue 142

[David P]

Current engine thinking is to move the wrist pin closer to the top of 
the piston and to reduce the length of the piston (shorter skirts) and 
zero quench (piston rises above the deck level). The 5th oil control 
ring served the purpose of (oil control) and also to minimize piston 
slap on the cylinder wall as the piston reversed direction leading to 
cylinder wall ovalization and subsequent loss of compression. Dave

On 4/18/2021 4:54 PM, Michael MacLean via Healeys wrote:
> I don't know about the six cylinder engines, but during the rebuild of 
> my BN2 engine I used 3 ring pistons from Moss.  Not exactly the most 
> exclusive examples of piston technology, but the very experienced 
> engine builder that built my shot block for me said they will do just 
> fine.  Heck I don't even remember seeing an oil scraper ring on them.  
> Not an expert, but could the way the bottom ring was ground to shape 
> have an oil scraping purpose?
> Mike MacLean
> Out of my five vehicles, only one has a catalytic converter.  Take 
> that Greta Thunberg.
>
> Sent from AT&T Yahoo Mail on Android 
> <https://go.onelink.me/107872968?pid=InProduct&c=Global_Internal_YGrowth_AndroidEmailSig__AndroidUsers&af_wl=ym&af_sub1=Internal&af_sub2=Global_YGrowth&af_sub3=EmailSignature>
>
>     On Sat, Apr 17, 2021 at 4:37 PM, William Atterbury via Healeys
>     <healeys at autox.team.net> wrote:
>     Hey Ian,
>     The rumor I heard was that the 5th ring was for hone-and-replace
>     rebuilds to reduce oil consumption.  I'll let others comment if
>     these cars were fitted with 4 or 5 rings from the factory (I'm
>     guessing 4).  I rebuilt mine with 4, like the others.  Not a
>     problem for our coddled Healeys.  Heck, I even know of one fellow
>     who only put in three for a hot motor.
>
>     Bill Atterbury
>     BT7
>
>     ----------------------------------------------------------------------
>
>     Message: 1
>     Date: Fri, 16 Apr 2021 19:08:56 +0100
>     From: "Ian Hey" <rianhey at btinternet.com
>     <mailto:rianhey at btinternet.com>>
>     To: <healeys at autox.team.net <mailto:healeys at autox.team.net>>
>     Subject: [Healeys] To fit or not to fit
>     Message-ID: <002201d732eb$915662a0$b40327e0$@btinternet.com>
>     Content-Type: text/plain; charset="us-ascii"
>
>     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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-- 
Porter Custom Bicycles 2909 Arno St. NE Albuquerque, NM. 505-352-1378 My World go here: WWW.PORTERBIKES.COM/

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