Another trick that some people might not be aware of......
On used stamped steel valve covers, same applies for oil pans and timing covers too, the bolt holes will dimple out when load spreaders are not used. You can turn them over, support them on a 2x4 or something like that, then use a small ball peene hammer to flatten the dimples back out. This allows the gasket to seal w/o getting spread apart by the dimple in the cover.
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