Just a NOTE, Tracy Smith dropped a valve at our RJ friends meeting at Byhalia in Sept. He broke the int valve head off on #2 cylinder about 1/2" up from the head. Luckly it went up into the valve pocket and didn't do a lot of damage to the head just a couple valve seats and some welding in the pocket. It didn't even punch a hole thru the piston, but beat it up pretty good. They were also Ferrea valves. I built the 388 short blk. but didn't install the heads. He was too tight on the valve to piston clearance. 6 holes was barely tapping the piston with the intake. I personally would not recommend less than .060 on the int. and no less than .100 on the ex valves. He says he checked the ex and they were around .080. Rocker geomertry was good according to him. He had .017 steel shim gaskets on a 48 CC head with flattop pistons, it's now costing him about $600.00 to put it back together, with .050 MLS gaskets. The short blk is a dirt cheap build, i mean less than $1,000.00 with cast steel crank, SIR rods and Hypereutectic pistons. Still in a 2950 lb Camero it ran best of 6.29 @ 108 MPH, with 1.27 60 ft times. (cam is special and i won't talk about it)
I'm not saying this was your problem, but i am saying that there may be a problem with some Ferrea valves.
Just making a point.
Zip.