BTW, I would not ever retard a cam just to lower DCR. It effects other performance aspects. Change the head gasket or open up the non-quench areas of the cylinder head since you are working on the heads anyway.
Interesting, I believe the reason that there is a 4 degree advance designed into the "centerline" of most cams is to increase DCR on most older engines. So would you agree that at least taking that out and installing them "straight up" on a fresh 10:1 may help things? But yes you are correct when retarding it affects performance by moving the power band up.
Opening up the non quench would help but you don't want to risk any thin areas. Head gasket will effect quench.
