Lycoming 0-320-D1F & D2F engines

[wrongway john]

This site shows that these two particular 0-320 engines have the 7.00:1 compression engines which allows them to use 80/87 octane gas, but yet still yield 160 HP, while all others using that compression come in at 150 HP.

Anybody know what the differences are that allowed them to still get the extra 10 HP for the 7.00:1 compression ratio?

[Mel]

If you notice the description column, it states that these engines have the high compression pistons.
Compression for these engines is actually 8.5:1.

[wrongway john]

Thanks, Mel. I noticed wikipedia words it the same, so I wasn't sure if there was something special about these two engines.

[Mel]

If you go to Lycomings engine specifications list, they are shown as 8.5:1.