If you haven’t disturbed the camshaft and crank, I can’t see there being a problem with cam timing. If you start with valve 1 fully open set tappet clearance on valve8, then follow the rule of 9. Not much to go wrong. Have you got the ignition timing set 180deg out? A very quick way to tell is to swap over leads 2 and3. If it was wrong it should start and run on 2 cylinders. However sometimes it’s just the rings aren’t bedded in yet and it may need a tow start first time. I used to replace rings quite often on the race car- sometimes it needed a tow start sometimes not but it would always start on the handle after that.
Alan Fairless