when you pay cheap you get cheap. those places are the reasion i got into doing my own heads. could not get a good valve job any where and then could not get good guide work.
frist you have to bronze wall the guides not replaace them with new cast iron guides if you want to run on unleaded gas. and dont even think about knerling it lasts about as long as it takes to talk about it.
then you have to do a good valve job that means holding seat runout to .001 or less not the .003 or more the factory says. and the valves should run no more then.0005 out. and yes you have to grind new valves.
if you get one of those cheap heads set it up and pour kerosene in the ports and see if it comes past the valves if it does you did not get a good valve job.
i did that and took the head back and the shop told me they will saet in when you run it a while. that was 20 years ago and i have been doing heads ever since.
