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Author Topic:   doesn't add up(compression)!
67fastback2+2
Journeyman

Posts: 92
From: Pennsville,New Jersey
Registered: Oct 2001

posted 03-05-2002 08:08 AM     Click Here to See the Profile for 67fastback2+2   Click Here to Email 67fastback2+2     Edit/Delete Message   Reply w/Quote
I am getting these results: 12-1 From Mustang and Fords, 11.3-1 From Ford Muscle and 9.5-1 From KB Calulators I can't understand the differences.
These are my #'s
Bore = 4.065
Stroke = 2.906
Top of piston to deck = .03
Flycuts in piston = 6 cc
Combustion chamber = 46.5 cc
Compressed gasket = .04
I have spent hours with different formulas on different sites tring to work this but I could use some help. Above are the base #'s thanks for any Advice!!! Pete

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V8 Thumper
Gearhead

Posts: 3366
From: Orange, Ca. United States of America
Registered: Dec 2001

posted 03-05-2002 09:12 AM     Click Here to See the Profile for V8 Thumper   Click Here to Email V8 Thumper     Edit/Delete Message   Reply w/Quote
hmmmm... Desktop Dyno comes up with 11.04:1, close (kind of) to Ford Muscle

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n2oMike
Gearhead

Posts: 1511
From: Spencer, WV
Registered: Jan 2001

posted 03-05-2002 09:41 AM     Click Here to See the Profile for n2oMike   Click Here to Email n2oMike     Edit/Delete Message   Reply w/Quote
10.16 to 1

cr = (swept + clearance)/clearance

swept volume = 3.1417 x radius x radius x stroke

volume of a cylinder = pi x radius x radius x stroke
swept = 3.1416 x 2.0325 x 2.0325 x 2.906
swept = 37.715 cubic inches
swept = 37.715 x 16.37 = 617.4 cc

clearance = deck clearance + flycuts + chamber + head gasket

deck = 3.1416 x 2.035 x 2.035 x 0.030"
deck = 0.39 cu. in.
deck = 0.39 x 16.37 = 6.4 cc

valve notch = 6 cc

chamber = 46.5 cc

gasket = 3.1416 x 2.035 x 2.035 x 0.040
gasket = 0.52 cu in
gasket = 0.52 x 16.37 = 8.5 cc

total clearance = 6.4 + 6 + 46.5 + 8.5
total clearance = 67.4 cc

c.r. = (617.4 + 67.4)/67.4
c.r. = 684.4/67.4
cr = 10.16

Yep, your compression ratio is 10.16 to 1
And yes, if your info is good, that IS your compression ratio.

Good Luck!

------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
http://www.mustangworks.com/cgi-bin/moi-display.cgi?220

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bluestreek
Gearhead

Posts: 1228
From: Athens,GA
Registered: Jul 2001

posted 03-05-2002 11:24 AM     Click Here to See the Profile for bluestreek   Click Here to Email bluestreek     Edit/Delete Message   Reply w/Quote
Your stroke number (2.906) and your deck clearance (.030) seen to be a little strange. Are these correct? .030 deck clearance plus .040 gasket clearance would give a total of .070 quench, which is kinda high for good combustion properties.

Anyway, I got 10.17:1 c/r given all numbers are correct and using 4.065 gasket bore diameter.

BS

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67fastback2+2
Journeyman

Posts: 92
From: Pennsville,New Jersey
Registered: Oct 2001

posted 03-05-2002 06:13 PM     Click Here to See the Profile for 67fastback2+2   Click Here to Email 67fastback2+2     Edit/Delete Message   Reply w/Quote
Thanks for the help!! Yes, I used a digital micrometer belonging to my machinest for the stroke and deck height(measured two sides then used the middle #). For the bore a published 4.005 then added .060 for the overbore. Thanks again!!! Pete


http://67fastback2-2.mustangsandmore.ws/

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TomP
Gearhead

Posts: 4780
From: Delta BC Canada
Registered: Dec 99

posted 03-05-2002 09:22 PM     Click Here to See the Profile for TomP   Click Here to Email TomP     Edit/Delete Message   Reply w/Quote
I have to question the 2.906 " stroke an offset ground 289??

and the .030" deck clearance is a lot too

somethings funny there

[This message has been edited by TomP (edited 03-05-2002).]

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