516 head question

I did a compression test on my 361 and found one low cylinder, so I am getting ready to have the original 516 heads redone. Nothing fancy, perhaps change out the 1.60 exhaust valves for 1.74's. I was thinking just a 3 angle valve and a plunge cut, and then just blending out any ridges left behind. I have been doing some reading indicating you have to be careful or you can get into water on these heads. I am enclosing a picture I found showing the kind of plunge cut I am talking about. There seems to be quite a hump in the stock exhaust port right next to the intake valve. Is this where they are thin, and should I be concerned about the plunge cut?

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I have done a number of sets of 516 heads and they can be made to work pretty good. The flow characteristics are totally different than the 915 and 906 heads and if you know how to port, they can work good. You have to be careful on plunge cutting those exhaust ports because that is the area that goes into water. Any core shift and you can have a hole.