Header Bolts for a 340

The end studs holes are drilled into the head coolant passages. If the studs come out and the coolant has not been drained below that level it will come out. If you remove these studs use Teflon tape or another sealant to prevent leaks on the end bolt holes on both heads.

Some aftermarket heads may not be drilled through to coolant but it is always best to check first.