How much will taking out the exhaust port bump give me?

OK, grinding comes to a grinding halt!

That is fine, I have lots of time to try to find headers that fit. Or save up for custom headers...

 

The P heads don't have a bump in the exhaust like the old heads, it's more of a crater in the roof. Serves the same purpose. You want to grind a straight line from the roof of the port opening to the highest point of the crater. See the attached cutaway photo. If you do decide to reshape the exhaust valve guide, be aware that there is a water jacket around it. Old heads this area was solid and you could grind it away completely. Not with Ps. Also you may have to open up the header gasket, I did on mine. The P heads have larger openings than even a 351W.

 

This is a cool thread.
Dan

 

bmcdaniel

Thanks for tha picture! That will be a huge help when I start grinding. It is like a "map" to where I need to go for the next few weeks.

I can easily reach the red, which is what you are talking about.

What about the orange area? Will this structurally weaken the valve guide? I am not sure if I can reach that area, or if I even want to do that much work to the heads.

 

Yeah, you want to take out the red portion and streamline the left orange area. The orange area to the right of the valve, in this case, is the heat crossover for warming up the intake manifold. As long as you stay away from the water jacket you won't weaken anything. The valve guide is flat on the end, it helps some to grind down the corner for a smooth transition from the valve stem to the guide (hope that made sense).

 

What is that cavity to the right of the valve stem on the cutaway? It appears that there is something broken and just jammed back into place at the end. Does that cavity serve a purpose or go anywhere?

 

Immediately to the right of the valve is the runner for the heat crossover, this must have been one of the head's center cylinders. To the right of that is the water jacket. Not sure about that funny looking area between them. Could just be the way they cut it on a band saw, or maybe he sectioned it to get an idea how thick the casting is there.

 

Check out progress so far. Using a dremel with a stone, and two different grades of barrel sanders. Pictures do not do it justice. So far, about 3 hours into it and one head is done. Still haven't got gaskets for gasket-matching. They are on order.

Despite seeing lines in the picture, and a dimple in the back, it is smooth to the touch, and the dimple (what is left over from the "smog-bump") is just a smooth indentation.

Any other suggestions?