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Burnt tacho cable

Posted: Sun Nov 04, 2018 7:41 pm
by Simon Whittley
Just doing a bit of engine work on my 356 and noticed by tachometer cable plastic sheath is burnt, presumably due to heat from the exhaust.
It still works so I'm looking for suggestions on how to protect it to prevent further damage.

Re: Burnt tacho cable

Posted: Sun Nov 04, 2018 9:22 pm
by Peter Poulikakos
You could try exhaust wrap.

Re: Burnt tacho cable

Posted: Sun Nov 04, 2018 9:47 pm
by Mike Wilson
Mechanical tach? It should be held to the left side engine tray with a P clamp.

Mike

Re: Burnt tacho cable

Posted: Mon Nov 05, 2018 3:03 am
by Juha Vane
Perhaps heatshrink tube could be the cure?
The better quality ones shrink quite much and
it’s available with glue and without.
The glue version is a bit stiffer.

If heat shrink tube won’t slip over the cable ends,
you could use self vulcanising tape. When you wrap
it around something the tape bond to itself and make
a perfect seal. Available usually at antenna shops.

I used insulation tube for my full flow oil filter
hoses, it is made in several diameters and
available at speed shops. You should first
verify that cable routing is correct.
And check that the tacho cable is not
a ground cable, that you have a good gound
cable between chassis and engine.

Re: Burnt tacho cable

Posted: Mon Nov 05, 2018 10:09 am
by Paul Ahnell
Simon: I had a similar problem and my temporary fix was to wrap the burned portion in fiberglass rafter insulation and then wrap that with thin sticky backed metal tape commonly used to seal joints and cuts in sheet metal heating ducts. See attached. Used a black tie wrap to attach the cable to the valve cover latch up and out of the way of the heat. Ain't pretty but it's functional until I install my new cable.

Re: Burnt tacho cable

Posted: Mon Nov 05, 2018 1:02 pm
by Dick Weiss
There's a hole (on the shelf's edge) to mount a clamp to hold the tach cable above the valve cover; Your location isn't correct.

Re: Burnt tacho cable

Posted: Mon Nov 05, 2018 1:34 pm
by Mike Wilson
That was my point regarding the clamp. Thanks for the clarification, Dick. Sorry I don't have a picture to post.

Mike

Re: Burnt tacho cable

Posted: Mon Nov 05, 2018 2:04 pm
by Paul Ahnell
Dick: Thanks for that. I wasn't aware of a clamp, etc. Don't think I have one. I'll take a peek at the parts book to see what's required to correctly mount my new cable.

Re: Burnt tacho cable

Posted: Mon Nov 05, 2018 2:07 pm
by Brad Ripley
From what I'm reading from Simon's post is that he has the earlier version of the tach cable which as has vinyl covering over the entire length. Apparently that vinyl covering is going bad from the heat of the exhaust.

The 356C version, NLA-741-311-01, has steel braided hose over the cable where it goes by the exhaust tube under the valve cover. This is the version currently manufactured and in the photo below. The hose piece is supposed to protect the cable from the heat.

And, as Dick points out, you will need the proper clamp.

Re: Burnt tacho cable

Posted: Tue Nov 06, 2018 7:50 pm
by Tim Berardelli
Aeroquip has a product called "fire sleeve" no need to reinvent the wheel.

Re: Burnt tacho cable

Posted: Wed Nov 07, 2018 2:11 pm
by Hugo Karasawa