In a message dated 02/08/2000 10:52:44 PM Central Standard Time,
pficklin@qnis.net writes:
<< Scott et al...
Here's CC data for my 1147...
(This is after porting & polishing, decking & shaving)
Bore: 2.728" + 0.40" = 2.768" (1.384" radius)
Stroke 2.992"
Head Combustion Chambers = 32.0 cc
Head Gasket "volume" = 2.4 cc
"DEAD" Volume = 34.4 cc
Cylinder displacement:
3.142 X 1.384" X 1.384" X 2.992" = 18.01 cubic inches/cylinder
18.01 CI X 16.387 cc/in3 = 295.13 cc/cylinder
Total displacement:
18.01 X 4 = 72.03 cubic inches
72.03 CI X 16.387 cc/in3 = 1180.36 cc (1180 rounded off!)
Compression ratio:
CR = (bore volume + dead volume)/(dead volume)
CR = (295.13 + 34.4)/34.4 = 9.58 compression ratio
I know, it can get rather anal...
>>
Well, there you have it. Not much more to say other than you might want to
add that your figures are accurate assuming you've "zero-decked" the engine
(i.e., pistons at TDC are flush with the deck). I believe that's what you
mean by "decking" in your note -- many readers won't have done that.
Otherwise, you'd need to add the volume between deck and top of piston.
Ted Schumacher gave me the ratio expressed as (V1 + V2) / V2, where "V1"
equals the volume of space above the piston at BDC (swept area, non-swept
cylinder area, head gasket space and combustion chamber) and "V2" equals all
space above the piston at TDC (non-swept cylinder area, head gasket space and
combustion chamber). That's the formula you've used as well.
Does that answer your questions Patrick? Craig?
Scott
ScottBarr8@aol.com
(once discovered, after doing the math, that I had a 6.58 CR b/c some GDPO
had installed a late [low-compression] TR6 head w/o shaving it down to GT6
thickness - 55 CC combustion chambers on a 2-liter engine instead of the TR6
2.5. Farging Bastiges. Gods that engine ran poorly!)
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