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Sorry to say this, but that head flow information may be misleading.
The exhaust flow through a stock port in a B20F head is approx 12% less than in a average B20E head. 12% may not seem like much but in terms of head flow, expecially stock, its pretty significant.
What's confusing is that the B20F head has an exhaust port that in modified form flows more than the B20E in modified form. So the B20F is the head to use for modifications while the B20E is the one to use unmodified.
Also, in terms of compression ratio you have to consider the thickness of the head gasket. The stock difference of 10.5 -1 vs. 8.7 - 1 CR was stongly influenced by using different head gaskets. The B20E used a gasket that compressed to .028
while the B20F gasket compressed to approx. .042 ( I could be a little off on this figure ). A current complication is that neither of these original gaskets are currently available. Yes, there is still a part number on the books for each, and yes you can order them, but the gaskets that you will get from Volvo or Elring don't have the original thickness. The B20E gasket is thicker and the B20F gasket is thinner.
John
V-performance.com
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