Help! Swapped 302 heads on my 318.

Kern Dog said

THis is the second time someone has asked this.
How could the valve spring height have any effect? The height of the tip of the valve does not change no matter what spring is in it. Once the valve is seated in the head, the height only changes if the valve seat comes loose or gets recessed due to damage.

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The height of the valves can absolutely change.

If the head is rebuilt with new valves they may not be the same height as stock, that’s easy.

Now the OP says all stock parts were used, but if the machine shop sinks the seats in the chambers when they’re installed the height changes.

Or the new seats that are installed are thicker and put the valves further out into the chambers.

Or both of those things happen. I picked up a “rebuilt” set of heads for cheap as part of another deal. Got them home and something didn’t look right. Laid a straight edge across the valve tips and they’ll all over the place, nothing lined up. Between the seats and valve job there weren’t two valves that came out at the same height. Not all machine shops are created equal.