Fergus,
The air injector thread size is 14mm x 1.5mm.
This is true for both 1600 and 2000 air injection
plug threads.
I do NOT recommend running a tap into the head,
as it is too easy to remove what little thread
are left.
Best way to "restore" the threads is to use an
old injector plug itself, and with a small jewelers
triangle file cut a couple of slots across the
threads. This will help clean and straighten the
exist threads in the head. Also known as thread
chasing.
On the plugs I make up they have a double step
at the bottom. This prevents the "coke bottle"
effect of just having a plug in there.
Tom
P.S. On the drill size to clean out the old carbon,
it was a 29/64" drill size. Only twist the drill
by hand, do not use a electric drill to "clean the
injection port" as it may remove the aluminum from
the head.
PPS: If anyone is after a set of aluminum plugs that
are specific to the roadster, I'll be able to make a
few sets up in the next two weeks... then it is back
to a "real job". $23.50 for the plugs & priority ship.
email me DIRECT for more information: twalter@austin.rr.com
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