Re: stripped spark plug thread

[frankr]

1954 25hp does not have an o-ring around the upper bearing. Check the vacuum passage between the bearing and intake manifold. It is supposed to suck any leakage back down to the intake. May be plugged up. I believe it is a mighty small hole at the bearing.

I’ve installed many Heli-Coils in heads with no problem. But I’ll defer to other opinions. BTW, you better have a mighty accurate torque wrench if you are going to tighten the plugs to 20. Just a tad more will strip them, especially if the threads are worn. This is one place I will bend and tighten them by feel.