Never mind.
 

The tangent of the angle has been solved

Call Dan Baisley and ask. He's the BEST there is at this point in time.

http://www.baisley.com/

ETA: Jerry Branch did my last set of custom heads but they were for a shovel chop. Ported, cc'ed, polished, double-plugged, 5-angle valve job etc. He can be found at Branch-O'Keefe.

These days I just run factory CNC ported heads on a 120R twin-cam street engine. Roller rockers, offset rocker plate, compression release, .658" lift etc.

I was always taught that it was the width of the contact and the duration of contact that kept the valves from getting too hot. 1 MM of contact is not enough, it always seems like around 2 MM is the sweet spot. If you have that and a solid edge that is not ground to a V, than back cutting of the valve itself seems like a reasonable thing to do. Never really heard of the 50 deg angle.

I will be interested in seeing what comes up in this thread.

Also consult with Zippers Performance / Elkridge Md. I'd have to do some research as to what is optimal in HD. But know they take quite the beating being aircooled, lots of valvetrain mass, lots of spring pressure if you are running any kind of modern profile cam. It's all about flow + longevity in a street engine.

As long as we are talking Jerry Branch and Zippers - two of the biggest, most respected names in the business, I thought I would throw out our Northwest locals for consideration as well. I've had great luck with the Baisleys in Portland, Oregon. Old man Wes, his son Dan, and now the grandkids do fantastic work. I'm running a set of their reworked heads on my '76 Sportster right now. Couldn't be happier.

You go son! Good info

No dyno test yet- but with the intake ports raised 1/2 inch up and 50 deg seats, the static CR has gone up a bunch.
It truly has affected the larger dynamics.
So much so I either have to retard the 530 cam, or install a larger LSA cam , which is what I will probably do. (like the 595 lift version)
I promise a dyno report by Spring.
It will be interesting to see how this has worked out.
Even I am interested in the devils in the details.