Is it clacking and making valve train noises when it runs like this? I had some heads done on a 440 years ago and the head guy put some crappy guides in it that would seize up when cold and hold the damn valves from moving!!! Clack on for about 30-45 seconds and they'd start to let go!!! I wasn't happy to say the least but he did fix it for nothing. Just asking from experience and your "head work" comment.