I just changed out the head gasket on my 87 Cherokee 4.0 which blew from over heating. Now that it's all back together I seem to have a misfire. I've checked the firing order, timing, vacuum lines and plugs. I noticed that #2 cylinder plug was fouled black while all the others looked normal. Could this be an indication of a valve problem or is there something more simple that I can look for? Also, I'm not to sure about the vacuum lines, can anyone tell me where I can get a legible diagram?

Any suggestions/input appreciated.

 

could be a valve problem, I would check compression, Also a old school trick is to hold a napkin or something up to the exhaust while running, if it trys to "get sucked up" the exhaust, then it is probably a valve issue.