originally the holes for the studs were a tight fit, requiring a wrench to install. every time the studs go in & out you lose a little bit of metal out of the holes. on aircraft engines they make oversize studs where the cylinder side is slightly fatter. I don't recall seeing that option on motorcycle engines though. best thing is to set the studs at the allowable top torque, with a thread locker and use anti-seize on the nuts. if you want to go with bolts on a permanent basis its best to helicoil the holes.
if I'm answering your question I assume the basic points have been addressed, such as: did you do a compression test? is it still on fire?