George Lendich wrote:
 >
 > Lyn,
 > Given we use slightly different descriptions for things, what is

Teflon

 > covered hook-up wire. Sounds good and cheap - do you over lap the

wire at

 > the joint. I'm a great believer in silicone as well.
 > George (down under)

I got the stuff at North American Aviation salvage years ago. It had a

fabric

cover over a Teflon, or Kapton insulator. I pull off the cloth sleeve.

The

conductor is tinned copper wire about 18 gauge. The diameter is just a

bit

bigger than the thickness of the stock compression "O" ring. After use,

the

insulator has nearly hydraulic locked in the groove.

The corners of the (now square) insulator are just barely rounded. The
silicone fills in whatever volume is left in the groove. I put the joint

near

the intake so there is no question about a compression leak. There is

only a

butt joint with a little dab of silicone over the joint. Other materials
might work just as well. The wire insulator material may make little
difference so long as it will hydraulic in the groove. Or bulk "O" ring
material might work as well. I was thinking about a piece of solid

copper

wire, but the stock "O" ring and the aircraft wire is all I can vouch

for.

Lynn E. Hanover

I was wondering about the solid copper wire too. Years ago as I recall the
double A fuel dragster engines used that instead of head gaskets.
The thing I wonder about is corrosion between the dissimilar metals over

time.

An 8 second dragster engine is one thing and aircraft engine is another.

Paul Lamar

 Lynn

 I wouldn't use silicone alone, but copper wire in Teflon sounds mighty
interesting. I figure that will be about as strong as you would get.
BTW how much silicone did you say you used - just enough for the join or a
little all around.
Sounds like there wouldn't be much room to fill and I wouldn't want to
stress the seal groove area.

Paul.
 I can't see how the copper wire would be touching the aluminium, it's
covered with Teflon.

George (down under)

It might work for awhile. Long term is what we are interested in. 
Teflon encapsulated silicone O-rings have been used in this application for years.
The problem with just teflon over a solid copper wire is teflon cold flows.
In other words you need something springy inside it to make it work.
Creavey has  teflon tubing with what looks like a tiny screen door spring inside
it for max temps of 800 F. 

Also somebody building engines all the time might
try solid aluminum wire. The problem with all these ideas is... nobody has
tested them for long term. It would take ten years to find out if it
really worked for our application. Race engines get overhauled with
regularity.

Paul Lamar
 
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