----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----
Hey Jason: I am not an expert, but in my opinion the problem/s with exhaust
stacks not fitting is two fold.
First, cylinder repairs are made over the
lifetime of these airplanes/engines. When the exhaust has been leaking on a
cylinder, the exhaust port gets worn down. If this is repaired by grinding it
flat, it changes the geometry between the stacks in a front to back condition.
Depending on which cylinder/s have been repaired in this manner, you can have
several different positions that the individual stack can end up in. It is
possible to make up for some of this through using different combinations of
gaskets, but one can still end up with internal stresses on the pipe, which may
or may not cause cracking.
Second, the pipes can be made from different
drawings. If the drawings are not EXACTLY the same, and if
there are even minor differences in the assembly fixture/s then the exhaust pipe
could end up being slightly different.
I know of a situation with the Alon stacks where an
individual made a 3 degree mistake which caused several sets of stacks to be
made incorrectly.
I believe the beads are caused by the exhaust gas
temperature melting the finish/paint on the outside of the stack. When it cools,
you end up with the bead/s.
Lynn Nelsen
============================================================================== To leave this forum go to: http://ercoupers.com/lists.htm Search the archives on http://escribe.com/aviation/coupers-tech/
