This is from an earlier post of mine:
The worst aftermarket heads i have seen were a set af Canfield sbc heads. The chambers were 3ccs oversize, the heads were warped .013", and the valves seated so badly light shined into the chamber was visible in the ports. Shortly after those heads I worked on a pair of bbc race heads. These heads were each warped over .014". I have also fixed Dart, AFR, World Products, Brodix, and Ford Motorsports heads. The defects i found were: guides too tight, valve guides not concentric to the seats, valve seats too wide, too narrow, and damaged by chipped cutter blades, seats contacting the valve face too far off the inside or outside, broken keepers, lubricant not present on valve stems, and more. My point is that ALL of these problems somehow got past quality control checks and made it into consumer hands.
The thing is this: Any of these heads would probably made decent power in spite of the problems because of the fact they are horsepower producing heads. A rough idle caused by leaky valve wouldn't be that noticable with a radical cam. But eventually a valve would stick or eventually burn or a head gasket would leak. I have seen each of these happen on heads that were bolted on. One head in particular was a bbc Dart head. The source where the head was bought from was advised that the valve seats didn't look right. The buyer was told to use them anyway. After little use on the drag strip, a valve head broke off from flexing as it tried to seat on an off-center seat. All I am saying is that if you spend $1500-$2000 or more on a set of heads, it would be wise to have them checked out by a good machinist. We do that for our
customers (while they watch) and they are more than happy to see that we found a problem before it cost them a lot more money in the long run.
After your previous experience, I'm sure you would rather check things our first............