On Tue, 10 Oct 2006 10:49:15 -0500, "Jim Burns"
wrote:

How are your engine monitor probe leads and wiring harnesses secured? Adel
clamps on the rocker box covers? Tie wrapped to your ignition leads? Tie
wrapped to the intake tubes? Adel clamps to the lower case/sump bolts?

I'm interested to hear about your installations. What you like and dislike
about the install location of the wiring harnesses and any problems
resulting from heat and or ignition or alternator interference. Do you have
service loops to allow you to swap probes or do you disconnect/reconnect
probes when you have a problem?

sig snip

This might get a little long, apologies in advance.

Tie-wraps really aren't the thing to use forward of the firewall.
Limited usage on wire bundles is OK, but waxed lacing cord works much
better in the long run.

A tie-wrap WILL eat into engine mounts, intake tubes, baffles, engine
cases etc. etc. over time. The life of the tie-wrap is pretty much
directly related to temp, if they are away from exhaust/cylinders,
they hold up OK on wiring, but waxed cord lasts the life of the
engine+.

Adel clamps and Koroseal lacing are the best way to go for securing
everything else. It takes a little practice to get the hang of tying
off Koroseal-stretch it too tight, it will break, too loose and things
move around. Koro seal withstands engine oil/petroleum products quite
well, and can stand most under-cowl temps, but too close to an exhaust
stack will cook it.

Depending on the engine type (I'm assuming we are talking AzTruck,
with intake and exhaust both on the same side of the cylinder), wire
runs need to be adapted to what you've got with regard to
intake/exhaust configuration, position of CHT wells on the cylinders,
baffle/cowling configuration etc. Bottom line is keep the wires secure
and as far away from the e-stacks as possible/practical

I would personally stay the heck away from spark plug gasket-type CHT
probes if possible. Regular spark plug maintenance takes it toll on
them.

You need to look your exhaust over and plot a course for EGT probe
positions. They need to be the same distance from the head, but often
can be rotated around the stack to a good spot to get to your wiring,
allow access for other maintenance, etc.

Often, cylinder head-located wiring runs are possible both outboard
(in relation to the crankshaft) and inboard of the rocker box. There
are typically bosses/threaded holes that might be used for baffle
attachment. Using an Adel on the outboard side is pretty
straightforward. Using them on the inboard side requires sourcing
fully threaded coarse thread bolts to extend beyond the "back" side of
the boss, using a lock washer and plain nut to secure the clamp.
Again, proximity to the e-stacks is an issue. Rocker box screws are a
last resort, they work in a pinch, but IMHO not too well.

Have used regular Adels on intake pipes, but on an Aztec they might be
pretty close to the e-stacks. I useta have a pile of clamps (might be
Piper, might be Lycoming, sorry, been too long) that had a relief to
clear a primer line, the ones for injector lines have a bigger relief.
They work extremely well for securing wiring to the intake pipes.

As you indicated, sump bolts.studs work well as an attach point to run
Adels/wires along the lower "inside" of a Lycoming. Just be careful to
replace any lock washers removed with new, maybe throw a thin washer
in here and there, and re- tighten any engine fasteners removed
carefully. BTW, if your stash of Adels have -3 holes in them and you
need to put a -4 bolt/stud through it clamp that sucker in a vise and
run a Uni-bit through it and don't worry about. BTDT again, and again,
and again, never had a problem.

Have never personally experienced any electrical interference issues
(call it EMI/whatever) with analyzers and alternator wiring, but that
doesn't mean that it couldn't happen. If I was doing the work myself,
I'd probably dummy up the runs along the alternator wiring with some
tie-wraps and do a ground run with the analyzer powered up and watch
the numbers.

I'd probably tentatively shoot for EGT on the outside bottom of the
cylinder heads and CHT along the sump and out the intakes, but you're
a lot closer to an Aztec engine installation than I am.

I'm not big on service loops or doubled-up wiring forward of a
firewall (unless it's darn close to the firewall, and not much else),
it's more crap in the way to get chafed/cooked/cut/boogered up during
service. I wouldn't screw around with probe swapping either-probes are
too cheap and labor (and the potential to screw up a "good" probe
trying to find a "bad" one. Keep new or proven serviceable spares (one
of each type installed), then once you install it, you can leave
it-worst case, you just swapped a probe out of your stock from a
serviceable one from your engine.

Running CHT's & EGT's (and Tanis heaters, for that matter) is just
like re-plumbing or re-wiring a standard engine install. It's kind of
a Zen deal. Once you seen what works and what doesn't work, you just
get a feel for it. Just don't get ticked if your master wiring plan
gets change by somebody that walks up and says "Um, wouldn't it make
sense to run those wires on the inside of that thingie there".

For the most part wires need to be SECURE from the firewall to the
point they transition to the engine (with a sort of "loop" or extra
material to allow the engine to shake) and then secure until they get
to the probe.

The bottom side of the cylinder will get awfully crowded with intake,
exhaust, spark plug, CHT probes, EGT probes, not too mention the
lovely little rod that ties the baffles together, just keep it as
"clean" and simple as possible.

Hope at least a little of this helps;

TC