My home inspection of Speedmaster heads

yellow rose said
The problem is the plug is so shrouded if you don't run 40 total (or more) you have something wrong.

That plug position is like retarding the timing 5 degrees or more.

Just purely for comparison, roughly measuring the radiused oval shaped unshrouding of the plug in the chamber of the TF’s, the oval is about 20mm x 16mm and no matter how the ground strap orients when tightened there is plug gap clearance 360 degrees. Hope that un-technical use of words makes sense!