Besides the valve sizes, are there any other physical differences between the two heads to look at? I am looking at a motor that is supposed to have PSO heads on it. Still bolted together. Are there any numbers or characteristics in the rocker area or on the outside to tell them apart?

The roof of the intake port is as high as physically possible on the pso heads. Level with the valve cover rail.

I see it. Like this. But was hoping something a little easier to see, like inside of the valve cover area.

That's what I'm saying. The intake roof area under the valve cover should be even with the top of the valve cover rail.

My PSO'S

Those are some really nice looking heads!!

No help to the OP...... Never had a set in my hands.

Had to have valve cover spacers to clear the raised rocker gear !!

I have a prototype intake that I didn't have to use spacers on RB style blocks but with everything moved up we had to make some !!

Quite sure my custom headers want work now along with the hood as everything was moved up and a tight fit...Will find out soon as I'm about ready to install the new bullet !!

Any dyno numbers! any specs on engine!

Man! Those PSO heads are HUGE!!!

588" nitrous deal with lots of quench & softened chambers along with lower compression...900" 55mm nitrous cam,Etc,Etc !!

Made 1100ish and was strong thru out the rpm band...My engine guy who is a NHRA comp elimator record holder and many time national & divisional winner was very happy as he felt we are leaving around 150hp on the table being a built for nitrous !!

We race a Limited jet 275 radial class and should be around 4.60-4.70 range with a .040 jet @ 3250#

Are those Slawko heads?

Would imagine Self is doing his own heads, but I have seen the Slawko CNC versions and they look similar. Good stuff for sure. Slawko will have a CNC Predator program soon as well.

And what exactly does "softening the chambers" mean?

Hard to tell in a pic...If you look at the difference in color in the chamber it's where they cut a small scallop on both sides to help in use of nitrous !!

Al is right both ways...Slawko cnc'd and Kevin Self hand finished ..Rare for Self to go behind someone but Slawko has a cnc program that got us way ahead in the game !!