My home inspection of Speedmaster heads
These RPM heads, and the copies have been around for quite a while now.
Tons of them have been on the dyno.
I don’t ever recall hearing of anyone having to run the timing at 40* to get the most power when using these heads.
I have to chuckle.......a few exposed threads around the plug has people in a tizzy.
But that big fat low flow valve job is a non-issue.