Do you set valve lash to spec in order to check the valve tip pattern for rocker arm geomtery with a mechanical cam? Or set the lash to zero to check for the correct pattern?

Don't know if its right or wrong but I always set lash first.

The approx. .020" lash will make very little difference in the contact pattern. On a 1.5:1 rocker this would equate to a .013" error in pushrod length.

it runs lashed ,so yes lash it .

The approx. .020" lash will make very little difference in the contact pattern. On a 1.5:1 rocker this would equate to a .013" error in pushrod length.

I will have to agree with you for once. I recently went through this and adjusted mine at both .020 and a 0 lash and there was no difference that I could really see with the naked eye.

Excellent, I checked with a cold lash setting.