[Healeys] compression ratio teaser

[PG]

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