The e6 heads sat the valve .1" (?) above where the e7 sits theirs. With enough time, the e6s can make almost the same power as the e7s but you have to really work the combustion chamber with the die grinder.
The twisted wedge also allows more lift because of the design and valve seat height
Gross valve lift is not why valves hit the pistons.
It is the opening and closing points of each valve that cause the contact problem.
When the piston is making it's way up during the exhaust stroke (pushing the spent gases out), the exhaust valve is near full closure as the piston approaches top dead center. Near this moment, the intake valve starts to open. Keeping in mind, both valves are open for a period of time.
This period of time is overlap.
Excessive overlap or particular exhaust closing and intake opening points can cause issues.
Steep ramp rates in racier combinations can cause issues as well.
The '86 pistons are at a disadvantage because they lack valve reliefs.
Thanks, and 5 spd gt I learned from you, I read it in the other thread you posted. Here are the heads that my friend is planning on putting on the 86 motor. Anybody running these? Opinions....