How much will cr raise if i shave the head 1mm?

I have a static compression ratio at 8.05 this is with a modified head and dished pistons.

This is so low because i originally think i drive with a 98 ron fuel, but now i'm thinking to use e85 because i had access to it, before i had no access to it, but now i had.

How much will static cr raise if i mill 1mm off the head?

It's a b21 engine.

And can i shave the head while valves are installed?

60 thou (1.5mm) off my b21f/398 head reduced the combustion chamber volume from 52.5cc to 46.5cc

edit: also I put bigger valves in which took up some volume.

Thank you.

Leave it low, add boost and fuel.

That is exactly what i will do, if i raise the cr i will buy a flat top pistons, it will make a -6.6cm^2 difference.
But for now i had to go and drive the car first.

Jussi Alanko said:

I have a static compression ratio at 8.05 this is with a modified head and dished pistons.

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If the chamber is modified no one can really answer this question for you, there's too many variables. My machine shop charges like $10 to pour a hole, which would be the best way to get a real answer.

Jussi Alanko said:

And can i shave the head while valves are installed?

Click to expand...

you can, but it's a bit of a lazy practice for an engine getting money spent on it.

Now i measured the cr and it is 8.45 with these pistons and a 1mm squish. if i put a flat-top pistons it will be a 9.2:1 which is good enough. I can't remove the valves because lashcaps are so thight and i can't get them out, so head milling is a no go to me.

I actually don't need torque at low speeds because i'm not gonna drive this thing in a city, so if my powerband is 3800-7200rpm then it is good enough, if this engine was an NA-machine the head will give max power output at 7840rpm, and my camshaft is a little too little to this, but i think when i eventually get this running i can raise the rev. limiter to 7500rpm.

I talked today at my head/camshaft guy, lvr-racing engines, who make engines to group f rallycars, and he told me that my engine should hold it up at 7500rpm in this configuration. So i can eventually get a 4000rpm good powerband, 3500-7500rpm!