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Compression Ratio/Cylinder Head Interchange

If you are thinking of changing the cylinder heads on your engine or are building an engine with a mix of different years parts, you may want to look at this chart to get an idea of what might happen to your compression ratio when you mix different year blocks and heads.

Engine/
Combustion Chamber
Volume(ccs)
45 54.5 49.2 53.5 63 58.2 60.4 58* 63* 69 55.4
221 8.7 7.6 8.2 7.7 6.9 7.3 7.1     6.4 7.5
260 9.9 8.7 9.3 8.8 7.9 8.3 8.1     7.4 8.6
63-64 289-2V 10.2 9.0 9.6 9.1 8.2 8.6 8.4     7.7 8.9
65-67 289-2V 10.6 9.3 10.0 9.4 8.7 8.9 8.7     7.9 9.2
64 289-4V 10.1 9.0 9.6 9.1 8.2 8.6 8.4     7.7 8.9
65-67 289-4V 11.5 10.0 10.8 10.2 9.0 9.5 9.2     8.4 8.8
65 HP289 12.3 10.5 11.6 10.7 9.4 10.0 9.8     8.8 10.3
64-67 HP289 12.3 10.5 11.6 10.7 9.4 10.0 9.8     8.8 10.3
68-72 302-2V 11.4 10.0 10.7 10.1 9.0 9.5 9.3     8.4 9.9
302-4V 11.3 9.9 10.6 10.0 8.9 9.4 9.2     8.3 9.8
73-76 302-2V 9.2 8.3 8.8 8.4 7.6 8.0 7.8     7.2 8.2
77- 302-2V 11.2 9.8 10.5 9.9 8.8 9.3 9.1     8.4 10.3
69 Boss 302               11.0 10.5    
70 Boss 302               11.0 10.5    
351W 4V 13.2 11.5 12.4 11.7 10.4 11.0 10.7     9.7 11.3
69-72 351W-2V 11.4 10.1 10.8 10.2 9.2 9.7 9.5     8.7 10.0
73-76 351W-2V 10.2 9.2 9.7 9.3 8.5 8.9 8.7     8.0 9.1
77- 351W-2V 10.4 9.4 9.9 9.5 8.7 9.1 8.9     8.2 10.0
80- 255 10.1 8.9 9.5 10.0 8.1 8.5 8.3     7.6 8.8

Notes:
* Interchange of Boss 302 heads to non-Boss engines is not practical.
Compression ratios shown in bold are for originally installed cylinder heads.
All information from HPBooks "how to rebuild your SMALL-BLOCK FORD ©1980"
The original table has been rotated to better fit on the page.

To identify specific combustion chamber volumes by head casting numbers, refer here.



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Lee Lafountain     This page is provided by MustangII.org

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