Let me start by explaining these are a set of ported E-heads that the valve job was done at a verry good local mopar engine shop a few years ago.At the time I had a solid roller cam and comp 938 springs.I can't afford to drop these off and get a complete valve job done on these and I don't think they need it.The margins where the valve meets the seat are clean and about a 1/16 wide.These heads were not run that long on the other motor.I got a spring hight tool and whithout a shim the installed hight is .915 and with the shim in place it is .885.Is the purpose of the shim to change the installed hight or to change the seat spring pressure?

Will both you change the install height with the shim your seat pressure will go up. But you will need a spring tester to make sure you’re getting enough seat pressure for the application. Also you don’t want to coil bind good luck with it.

Before you do anything else you need to know what seat pressure and open pressure your cam manufacturer recommends.

R.