There are a few ways to lower the compression ratio, you can use a shim(spacer) plate that goes in together with the head gasket. i have also heard of people using 2 head gasket to gether to do the same job. If you're planning to built a reaonably low boost set-up this method is fine as long as you don't go overboard.


Or you can have the pistons and/or head machined to reduce the compression ratio,i.e dishing the pistons etc, i would recommend this method for higher boost applications.

If your doing any sort of engine work i would recommend a suitable turbo cam, i'm pretty sure you can get on from a decent cam place, crane or crow would be a good start. I would recommend a full rebuild if you're going that far.