Standard 6 cylinder Healey engines do not have dished pistons. They have flat
top pistons.
Richard Mayor
BN7L-466 Vintage Racer
Portland, Oregon
> From: austin.healey@gmail.com
> To: britishcars@shaw.ca
> Date: Wed, 13 Jan 2010 03:43:04 +1100
> CC: healeys@autox.team.net
> Subject: Re: [Healeys] compression ratio teaser
>
> Hi Paul, a standard 6cyl Healey has
> 1. dished pistons, and t
> 2. The tolerances used by BMC in the 1960's meant the pistons don't
> actually come to the top of the bore.
>
> I didn't check your combustion chamber volume, I don't have a STD head
> lying around. But I suspect your calculation didnt account for:
>
> 1. you need to add the piston dish: and
> 2. Add an allowance (similar to the head gasket allowance) for the
> piston not being flush with the block deck
> In order to get the correct std compression ratio
> Are you coming to Australia again in the near future?
>
> Now my divorce is finalised, I have that pair of Wolseley front shocks
> if you are still interested....
>
> Chris
> www.myaustinhealey.com
> Sent from my iPhone
>
> On 11/01/2010, at 5:16 PM, "PG" <britishcars@shaw.ca> wrote:
>
> > Hi List,
> >
> > I'm having a tough time reconciling the calculated theoretical/static
> > compression ratio of the later model Healey engines with the
> > published ratio
> > of 9:1.
> >
> > Here is my math:
> >
> > Stroke 3.5" (88.9mm)
> >
> > Bore: 3.281" (83.34mm)
> >
> > Calculated cylinder volume Pr2*h: 485mm per cylinder or 2910 for the
> > engine. So far so good!
> >
> > For the compression ratio:
> >
> > Combustion Chamber volume: 53mm
> >
> > Gasket volume: 2mm
> >
> > Therefore, calculated compression ratio becomes:
> >
> > (53+2) / (485+53+2) = 9.82:1
> >
> > Supposed to be 9:1 !
> >
> > Any of you geniuses see what I'm doing wrong??
> >
> > Paul
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