compression vs octane

[Jim_Pat]

Knowing that there is a weight & load consideration but is there a compression to octane requirement. I have 4 200hp heads I will be putting on an 88/92 open deck 225 looper with the stock gaskets. These are the 2.7 heads with the smaller combustion chambers (333108). Not a 100 percent sure of the deck height but I think I'm in the hole. These are stock block configuration. Going to check deck height when I pull the heads. Current heads are the 809 64cc heads 75/80 compression hoping to see 120/130 compression. Motors are on a eliminator 23 Daytona with 28 Mazco's,

Thanks

[58Evinrude]

You won't get that high a change in compression. Or at least I didn't when I did the same head swap. Mine went up to about 105 to 110, but its high enough that you'll need to run 91 octane at least. I got caught out and had to fill up with 87, and fried a piston about 10 minutes later.

[frank jackson]

check the depth of the 2.7 heads ... the clean gasket surface to the closest you can get to the plug hole should be .700 deep . you can run 91/92 . If its less than .700 you need more . Also start richer on the mains ...

[Euroski]

You won't get that high a change in compression. Or at least I didn't when I did the same head swap. Mine went up to about 105 to 110, but its high enough that you'll need to run 91 octane at least. I got caught out and had to fill up with 87, and fried a piston about 10 minutes later.

Did U limit your RPM lower with the 87 fuel?

[58Evinrude]

Did U limit your RPM lower with the 87 fuel?

No, I was an idiot and ran it wide open. Not for long

[racer]

Added compression will need 91 octane but they will also need to be jetted correctly and have the timing set at 16 to max of 18 degrees.