I have a 72 GS 455, but she wont start. I just drove her yesterday no problem, then i get back in to start an hour later and she doesn't fire. The engine turns just fine, but it seems as if there is no fire. I have adjusted the timing both ways to try to compensate. No fix... I just replaced the ignition coil, but it is still doing the same thing. Any tips on what i can do to fix this problem?