Compression ratio improvement for an 4L engine

[Kassi]

Hi,

I bought a new 4 L engine for my SD1, actually running well with SU carbs and BW Automatic, standard 3.9L cam. I already tried my edelbrock carb and found a huge increase in acceleration, but I have to improve the selfmade assembly first.
Now I think about tuning the 4L engine, especially skimming off the heads at 3 mm, getting a compression ratio of about 9.55:1?
Because it's a new engine, I don't want to change too much.
Also I want to stay for 95 octane fuel, Super. And what's with the timing?
Has anybody experience in the 4L engine and can tell me, if 9.55:1 is o.k or if I can go for more?

[katanaman]

I would say you can go for more but I would also say skimming your heads is going to give you way more compression than your thinking its going to. 1mm is approximately a change of 0.7 in the ratio. Assuming you don't have a low comp engine 3mm will get you roughly 11-11.5:1 which IMHO is too much unless your going for a radical cam.

[Kassi]

Sorry, my mistake, I meant skimming 0.3 mm. According to your calculation this would lead to a compression ratio of 9.55:1, as I had assumed.
What's with the timing in this case. Actually its 8° degrees advance statically.