NASSEX

I started with a 9:1 c/r 1.8l from a '94-95.
the block has already been overbored by 0.5mm to fit oversized pistons.

With a goal to get as close to 11:1 static c/r as possible,
The question is if I shave the cylinder head to gain 9.5:1 compression, would that mean that I'd need 10.5:1 pistons?

I'm also not sure if the overbore will affect the compression ratio because they were aftermarket oem replacement pistons and didn't specify. Either way later on I plan to get forged pistons so that's why I'm wondering if I should get 10.5:1 pistons to achieve the 11:1 end result.

Thanks in advance for sharing knowledge

rascal

Compression ratio is much better achieved solely through pistons rather than shaving and pistons.
if you are purchasing pistons anyway, skip the shave and buy 11.0:1 pistons straight up

most people only shave their heads (to up compression) to avoid buying new pistons…

NASSEX

So I want to skim the head a little bit anyways because I don't plan to buy pistons for atleast another year and a bump in c/r would be nice to add some efficiency for the time being. I have just the head off right now due to needing to clean the valves and replace valve stem seals.
and not taking apart the bottom end until next next season.

My bottom end (no pun) has just 19k miles and the head has 219k.

I appreciate.the advice. I should probably redo the first post.

what are the inherent risks with skimming the head to gain 0.5 c/r from 9:1 aside from valve clearences and needing a better tune? Technically speaking. Like is there a risk to anything else if I had it skimmed that much? What's considered a lot? What's considered medium o.O..
oh and the big question is wouldn't it be better in the end to split it between pistons and cylinder head because higher compression pistons have extra weight added to them, similar to how oversized pistons do.

NASSEX

Why?

I am avoiding buying pistons for the time being. Maybe at least for 1-2 years.