400EX Head studs will pull the threads loose in the cylinder anytime
that the cylinder gets too hot breaking down the aluminum. There are
several causes of this including overheating of the cylinder during
resleaving and poor matching of fuel octane to the engine.
These heavy duty studs cannot be used if the cylinder was drilled and
tapped for Helicoils or drilled and tapped for any other oversize studs
with a differant thread diameter and pitch.
need to first drill and tap the cylinder to accept the new studs.
course thread. Drill holes with a 3/8 inch bit. It is always best to have a
machine shop do this procedure in a vertical mill to ensure proper
sure to hone cylinder after studs are installed.
the new studs using Permatex sleeve retainer on the threads.
sure to install to the correct height.
studs must be the correct distance out of the top of the cylinder.
Stock vs. Heavy duty