This info was originally submitted by Mahlon Russell:
Quote:
7:1 compression ratio, in an O-360, is had by installing 75413 or equivalent pistons and it is generally accepted to burn mogas with 87 octane and above with that compression ratio. Take off Hp is in the range of 168 with those pistons.
8.5:1 is the standard compression ratio for the O-360 and it is attained by use of 75089 or equivalent pistons. It is generally accepted to run mogas of 91 octane and above with this compression ratio. Rated power is 180 HP with those pistons
9:1 compression is attained by use of the LW-15357 or equivalent, in the O-360, and it is generally accepted that you should use 100LL r above with this engine. Normally see around 185 HP at take off, with those pistons.
The 320 and the 360 have the same bore, only the stroke is longer on the 360 to get the extra displacement. So you use the same pistons to get the same compression ratios for the 320 as with the 360.
7:1 compression ratio, in an O-320, is had by installing 75413 or equivalent pistons and it is generally accepted to burn mogas with 87 octane and above with that compression ratio. Take off Hp is in the range of 150 with those pistons.
8.5:1 is the high compression ratio for the O-320 and it is attained by use of 75089 or equivalent pistons. It is generally accepted to run mogas of 91 octane and above with this compression ratio. Rated power is 160 HP with those pistons
9:1 compression is attained by use of the LW-15357 or equivalent, in the O-320, and it is generally accepted that you should use 100LL above with this engine. You should see around 164 HP at take off, with those pistons.
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