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2/13/2007 |
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Flathead
Ford Compression Ratio |
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flathead
comression ratio.xls © 2003 Roadrunner Engineering Albuquerque, NM |
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Head |
Baron 500 |
8CM |
8BA |
EAB |
Offy 425 |
Edelbrock |
Offy 400 |
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Dimensions |
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HV (cc) |
92 |
82 |
76 |
71 |
63 |
61 |
54 |
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Displacement |
Relief |
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Bore x
Stroke |
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Cu. In. |
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1) |
239 |
no relief |
5.9 |
6.4 |
6.8 |
7.2 |
7.9 |
8.1 |
8.9 |
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3-3/16 X
3-3/4 |
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relieved |
5.8 |
6.3 |
6.6 |
7.0 |
7.6 |
7.8 |
8.5 |
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swept
volume 490 cc |
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2) |
249 |
no relief |
6.1 |
6.7 |
7.1 |
7.5 |
8.2 |
8.4 |
9.2 |
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3-1/4 X
3-3/4 |
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relieved |
6.0 |
6.5 |
6.9 |
7.2 |
7.9 |
8.1 |
8.8 |
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swept
volume 510 cc |
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3) |
255 |
no relief |
6.2 |
6.9 |
7.2 |
7.6 |
8.4 |
8.6 |
9.4 |
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3-3/16 X
4 |
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relieved |
6.1 |
6.6 |
7.0 |
7.4 |
8.1 |
8.3 |
9.0 |
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swept
volume 523 cc |
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4) |
265 |
no relief |
6.4 |
7.0 |
7.5 |
7.9 |
8.7 |
8.9 |
9.8 |
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3-1/4 X 4
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relieved |
6.3 |
6.8 |
7.3 |
7.6 |
8.4 |
8.6 |
9.4 |
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swept
volume 544 cc |
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5) |
276 |
no relief |
6.7 |
7.3 |
7.7 |
8.2 |
9.0 |
9.2 |
10.1 |
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3-5/16 X
4 |
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relieved |
6.5 |
7.1 |
7.5 |
7.9 |
8.6 |
8.8 |
9.7 |
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swept
volume 565 cc |
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6) |
284/286 |
no relief |
6.8 |
7.5 |
8.0 |
8.4 |
9.2 |
9.5 |
10.4 |
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3-3/8 X 4
or 3-5/16 X 4-1/8 |
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relieved |
6.7 |
7.3 |
7.7 |
8.1 |
8.9 |
9.1 |
10.0 |
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swept
volume 582-586 cc |
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7) |
293/296 |
no relief |
7.0 |
7.7 |
8.2 |
8.6 |
9.5 |
9.7 |
10.7 |
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3-5/16 X
4-1/4 or 3-3/8 X 4-1/8 |
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relieved |
6.9 |
7.5 |
7.9 |
8.4 |
9.1 |
9.4 |
10.3 |
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swept
volume 600-605 cc |
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8) |
304 |
no relief |
7.2 |
7.9 |
8.4 |
8.9 |
9.8 |
10.0 |
11.0 |
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3-3/8 X
4-1/4 |
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relieved |
7.0 |
7.7 |
8.2 |
8.6 |
9.4 |
9.7 |
10.6 |
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swept
volume 623 cc |
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Notes: |
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1) See Blown
Flathead, Appendix B for more information on calculating flathead
compression ratio. |
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2) All
heads should be checked for actual combustion chamber volume of the head
only. Values listed are typical. |
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3)
Compression ratios listed are for domed (3/16 dome) pistons. Flat top pistons
should not be used with listed heads. |
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4)
Compression Ratio(no relief) = (SV+HV+8)/(HV+8) |
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5)
Compression Ratio(relieved) = (SV+HV+11)/(HV+11) |
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