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Jack, I ran into the same problem just last month. On my B, I did an overhaul, but I used a Clevite kit. 3-1/8 high dome pistons, so I ended up with 123 Cubic inches too. The pistons I took out were M&W Add Power's, also 3-1/8 high dome, but the shape of the dome was just a little bit different. When I put it together, I torqued the head and when I turned it over to set the valve lash, it stopped dead. The edge of the domes hit the step on the head in each combustion chamber. I talked it over with my local IH tractor guru and his opinion was that somebody probably planed the head sometime in the past. He said he had run into it before and his solution was to just grind out enough from each combustion chamber to clear the pistons. He reccomended that I NOT take any off the pistons because they are weight-matched and I had no way to re-weigh them accurately, so there was no way to be sure they were all the same weight. I had a machinist take a little off the head in each combustion chamber, then put the head back on without the gasket, and put a piece of masking tape on the spot that was hitting to make it easier to see what was hitting together.
The head before machining. The pistons hit that right angle edge.
[IMG]http://i16.photobucket.com/albums/b16/RedDave/th_CombustionChamber2.jpg[/IMG] The pistons. They hit just on the near edge about halfway up the raised part. [IMG]http://i16.photobucket.com/albums/b16/RedDave/th_Piston3.jpg[/IMG] This is the head after the machinist took a little out with a milling machine and a slight adjustment with a die grinder. [IMG]http://i16.photobucket.com/albums/b16/RedDave/th_HeadAfterMachining3.jpg[/IMG] After enough was out, I put it back together and it has been running just fine. I don't know if the pictures will show up or not.
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