As above, I have just had a full head rebuild put the head on with new gp A gasket ,bolts etc and i managed to get the timing mark wrong on the crank pully. When i turned it over it locked up,so i checked and re-alined timing ,and when i spun the engine over i did a compression test and i have a lost all compression on number 4, so i have fucked a valve or 2. So as the engine has not ran can i use the gasket again?