Join Date: Jan 2003
Location: Halifax, NS, Canada.
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There is a really good thread on this topic somewhere on here from a while back that had some good input from smp performance that surprised some of us. I think Stefan determined that the swirl head was ultimately more resistant to detonation, and was arguably a better choice on a high boost engine... I was unable to find the thread though.
I am running a G head now on swirl pistons, but I made some other changes when swapping from the 782, so I can't objectively campare the two. The G head, all other things being equal, will allow your to run more boost and also require you to run more advance. If you can, get a cal designed for a G head. You can simply run more initial advance on a swirl cal (anywhere from 14*-18* depending on other variables) but a G head cal would be better.
BMW ZHP Imola Sedan