On going learning saga.. installed a HEI distribitor on my 235 engine. Previously installed a new starter and got it to start with a rough idle and backfire. Ran for about five minutes than shut it off and week later installed new HEI. Now that the new distribitor and coil and in place it cranks but does not start. Occassional pop and backfire. Where to start troublshooting? Would it at least start even if the timing is off ? Thanks, Scott