I've got a '73 FL, on the rear cylinder the exhaust stud keeps backing out of the cylinder head. I even tried putting a regular exhaust bolt in the head. But that two eventually backed it self out. What is the best way to get the studs or bolts to stay in the head, to maintain a tight seal for the exhaust?

 

Put the stud in the head(not the bolt, a STUD) with red loctite, then tighten down your nut. Also make sure your exhaust is supported well, you should be able to back off your nut that holds the flange up to the head without the flange pulling away from the head. if it does, you will have to modify or adjust your hangers for the exhaust.

 

if it still does it then id helicoil the heads then install a stud. the helicoil is going to be steel and stronger, an old harley mech. did this to his and never had a problem.

 

d_slat has it right, make sure that the exhaust fits flush without tightening the nut. The exhaust bolts were never intended to support the weight of the pipes.

 

I still have Allen bolts going into the heads on my Lowrider and don't have a problem but they are Helicoiled in which is more solid than just the 5/16" Alum stock threads.

 

Sorry I don't have pics, but an old fix was to use a longer Allen bolt in place of the stud and add a lock nut. I'll try to explain ...... The allen bolt needs to be long enough to be able to add a jamb nut. Remove the stud or bolt from the head. On the new allen bolt, thread on a nut all the way to the head of the bolt. Position the pipe and thread the bolt through the pipe into the head and tighten (with loctite). There should be space now between the nut and the exhaust pipe flange. Now, while holding the allen bolt with a hex key, tighten the jamb nut against the exhaust pipe. Mission accomplished.