Exhaust Air Injection Plugs - Again!

[jlandry@domain.elided (John A. Landry)]

Binder Buddies (hey... maybe the next Christmas craze?)...

Ya know those plugs some of you have been installing in your cylinder heads
to block off the air injection ports in the exhaust?  Well, can someone
please describe these to me?

Here's why I ask... I have a set of 392 heads that had these ports blocked
off with sure as heck looks to me like regular old 1/4" NPT pipe plugs.
When I was removing them the other day, they seemed to only be screwed in
about two or three threads at best.  Not a very secure fit and it looked as
though they might have been leaking a bit.  I thought maybe they were added
after the engine left the factory, but they had evidence of IH red paint
still on them, so I'm wondering if they were or wren't there from the
factory.

I seem to recall some discussions on the list about how the proper Navastar
plugs have a special thread taper and they screw in deep enough to almost
completely fill the hole in the cylinder head.

I called the local Navastar dealer, and they don't stock the plug for me to
look at.  It's special order and about $4.00 each.  I'm not about to
special order the plugs if they're the same ones I already have.  BTW, I
dug up Navastar part number 484815-C1 from past Digest archives.

Thanks,

John L.
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