You suppose that after a couple of valve jobs the valve could be sitting quite low in the port Panic???? If the exhaust seats are badly burned by the time they clean up again the valve can sit quite low. With the valve sitting lower in the seat you need more shims to bring the springs up to the proper pressure and it also increases the combustion chamber volume lowering the compression.
New seats bring it up to the proper height in the combustion chamber. And there is always that simple fact that the new hard seat is gonna last a lot longer than the much softer cast iron seat.
You can also skimp on the guides and knurl them, if you just want it to run, but if you want it to perform like new, plan to spend a little more and do it right.
Denny Graham
Sandwich, IL
