I'm planning on milling my head .04 or .03 and was wondering if I would have to run it on higher octane fuel or would it be ok on regular.

 

You should be running premium already.

 

I phrasef my question incorrectly. I realize im going to have to run 91 but would I have to run higher?
Just to let you know I'm pretty sure a stock crx is ok to run 87 on. Plenty of people do it without any knocking or pinging.

 

You're right. 87 octane is what you SHOULD be running. People stupidly think that higher octane = higher mpg. They couldn't literally be more wrong. Higher the octane the more it resists detonation. Google that last line for more information.

Someone should chime in soon about what octane to use after milling though.

 

On my daily I believe it was .030 off the head with .5mm overbore, I'm doing just fine on 87. If you want to be reasonably certain you'll be ok, starting filling up on 91 now before you do the work. After the fact, you should be able to retard ignition timing if you are hearing knocking. If not, you can start to add 89 in little portions to dilute the 91. If you don't hear any knocking, repeat with 87. If you do hear knocking, you know you have to stick with 91 (or 89 if you get to dilute with 87, hope that makes sense).

You can also play with a compression calculator to see what you might end up at with respect to your engine's compression ratio. Honestly with all else being equal, I don't think you'll need 91.

 

Your right don't know why I had B-series on the brain

 

Yeah from what I read the jdm bseries need 91 minimum. That sucks with gss prices these days.