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Chart Explaination "How to rebuild Small Block..."

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Ok, I've been reading my "how to rebuild small block ford engines" book, and found a chart on page 38. It is a Compression Ratio/Cylinder Head Interchange chart.

Could someone please tell me how to read this? The horizontal axis has all the different engine years and sizes... (starting with 221, hitting the 289, 302, 351, Boss 302, etc)... The vertical axis has Combustion Chamber Volumes. starting at 45 cc and going up to 69 cc. Numbers in bold face on the chart are for originally installed cylinder heads... now lets use my '78 302 as an example.

45cc = 11.2, 54.5cc = 9.8, 49.2cc = 10.5 and so forth.. the bold value for my heads is 69cc = 8.4

Ok... Now I want to get, say... 1970 351W heads (wow, where does this stuff come from? *grin*) I look at the chart, and it has different values... the original installed number is 60.4cc = 9.5

Ok, so if I put those 351 heads on, as stock, am I going to go from 8.4:1 compression to 9.5:1 compression? am I reading this right? Someone, please explain this. I keep hearing by adding 351W heads to a 302, I'll lose .5 in compression... where does that come from? I don't see it anywhere on this chart?

Rich
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'66, 302-4bbl, Granada disk brakes, etc, etc...
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