<VV> Compression ratio for 140HP Engine

[BobHelt at aol.com]

In a message dated 8/3/2007 12:31:23 PM US Mountain Standard Time,  
nicolcs at aol.com writes:

Also  cylinder seating surface depth in inches for
same, and anything on squish  or quench area  to piston top clearance for
optimum turbulence with  out risk of detonation using pump gas (91 Octane
max). My performance book  says around 0.025" is optimum, although, this book
was published many years  ago when we had higher octane fuels (including
leaded fuels) at the  pump.


while 0.025 is considered optimal by many, there are some other things to  
consider. First is the type of rods/pistons you plan to use and what will be  
your max rpm. The question here has to do with elongation of the rod/piston at  
high rpms and possible contact with the head.
 
Second consideration deals with stock engines and possible oil consumption.  
That is, what will be the life expectancy of this engine. With only, 0.025, 
any  carbon or other deposit build up in the cc may raise the cr too high, or 
maybe  even allow some piston to head contact.
 
Most Corvair people go for the gap of just the head gasket thickness, or  
around 0.032 in. for a stock gasket.
 
See RA Kirkman's head article in the Tech Guide for cc volume and data for  
calculation of the gasket step thickness.
 
Regards,
Bob Helt



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