Quote: It seems like the closing clearance can only open up with heat since the valve will grow, but the growth of the head from the seat to the cam shouldn't be an issue due to the 90 degree closing rocker
This is what I’m thinking. The head of the valve grows first as it is closest to the flame. As it gets bigger in diameter the valve would move towards the combustion chamber decreasing clearance even though the overall length of the valve gets longer. The key here is the head is growing in diameter so it pushes away from the seat. Think of it as the opposite of valve recession where the valve sinks into the head.
If the seat grew in diameter at the same rate it would cancel out.
As the stem warms up and gets longer clearance comes back. I don’t see how the shape of the rocker plays into it.
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