The frontmost bolt of my exhaust manifold keeps backing itself out, despite swapping it with different grades of bolts. Loktite probably wouldn't withstand the heat, and wouldn't a split washer just expand and contract with the rest of the metal and eventually back out anyway? Any ideas?

 

i recently did swapped my manifold out for a better one and never had issues......
are you sure your torque-ing them down enough??, may be a dumn question but i figured i'd ask

 

try a lock washer. it wouldnt suprise me if it worked

 

This might sounds crazy but it works. Put a little dab of super glue on the end of the bolt it really does work suprised me.

 

CA glue will break down in the heat, as will most grades of LocTite.

Use LocTite #272 - it's formulated for exhaust heat. And, make sure the little "dish-shaped" washer under the screw head has been replaced - it's there for a reason (the tension it provides will not only help to retain the screw, but it will also allow some expansion room for the different expansion rates between aluminum and iron.)

Torque to, I believe, 19-21 pound-feet.