Re: plug

[Steve Stegmann <stegmann@domain.elided>]

Paul,

The chirping noise is made by the exhaust blowing over the holes left by 
the removal of the air injection piping.  When you plug these holes with 
short bolts you get the effect of blowing over a soda bottle.  Except 
that the "bottle" is about 1/2" dia and 1" deep, and of course the 
exhaust is moving pretty fast.  The resulting whistle occurs once on each 
exhaust stroke, is high pitched and doesn't last long.  The effect is 
sort of like "pinging" but not quite.  You can tell the difference. You 
hear it as you get on the gas. You can't hear it at idle, even standing 
next to the engine, or on steady cruse.  As you get on it or climb a hill 
you begin to hear it.  It occurs at the same time as pinging usually would.

If your engine never had air injection, chances are the holes are 
already plugged with the proper plug.  49 state versions got air 
injection in '79.  Calif got it in the early '70s.

I've ordered the plugs from the local Navistar dealer.  I'll post the 
results probably Monday after I've installed them.  The part number is 
484815C1 and they are $4.34 each! I need six, two of the holes were 
plugged and not used for the air injection, go figure.

Steve

----------------------------------------------------------------------------
Steven A. Stegmann
     _/_/_/    _/      _/_/_/ "No free man shall ever be debarred the use
   _/    _/   _/_/   _/    _/  of arms.  The strongest reason for the 
   _/        _/ _/   _/        people to retain the right to keep and bear
    _/_/    _/  _/    _/_/     arms is, as a last resort, to protect 
       _/  _/_/_//       _/    themselves against tyranny in government"
 _/    _/ _/    _/ _/    _/    
 _/_/_/  _/     _/ _/_/_/         Thomas Jefferson, June 1776
----------------------------------------------------------------------------