Grrrr.
I soaked a head in Diesel for a full week, but it wasn't coming clean very easily. So I took them to a shop and said "clean 'em, do the guides, do the seats, and surface them."
I came back the next day, and they only surfaced the heads. I asked why, and they said they need the valves to check the guides. I said I had measured them two different ways and they're loose, just do them. They were adamant that they needed the valves. So (instead of walking away like I should have), I brought them the valves the next day.
Came back to pick them up, and they said proudly "We didn't even measure them, we wiggled them, they're mint!" You suck, machine shop, you suck. They did cut the seats, but they ended up cutting them pretty deep and now there is a deep ridge around the valves hindering flow.
See the edge above the top cut on the exhaust? Ugh.
Thing is, seat cutting is referenced off the guides. If I do the guides now, the seats have to be re-cut as they will not be concentric with the guides, and then the valves go deeper into the head. Grrr.
I thanked them, paid them, took my stuff, and I'll never go back, nor will I ever recommend them to anyone else.
I recognize I'm not a professional machinist, but dang it, just do what I ask and bill me accordingly. At this rate, though, I may eventually run out of machine shops.
So, I spent a number of hours re-shaping the valve seat area in the combustion chambers to get the flow back, and figured while I'm at it, why not polish the combustion chambers?
Since I didn't have any old valves, I turned down some round stock to 0.313" and threaded one end 1/4-20, and cut out some 1/8" flat and turned them to protect the valve seats.
Research indicates possible advantages being:
More combustion heat applied to piston
More heat kept in exhaust to spool the turbo faster
Less carbon build up
Less "edges" risking pre-ignition and detonation
Could also be pipe dreams and voodoo.
I polished the piston tops as well. Because why not. My labour is free.
After a fair bit of research and debate, I likely will not hog out these heads with porting. I think the swirl ramp in the intake bowls is a good idea for low-speed throttle response, torque and fuel economy. I haven't decided if I will remove the rocker-stud boss in the intake port (done on pretty much all ported and aftermarket heads).
Of course, on one side of the fence you have "Awesome! That's the best mod you could do right there!" and on the other side you have "Dude! You just ruined those heads." Well, I did what made sense to me. We'll see if I get lucky.