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Re: Return of the unleaded thread

To: egilk@oslonett.no
Subject: Re: Return of the unleaded thread
From: bc620@scn.org (Ernest G. Janzen)
Date: Thu, 26 Oct 1995 08:27:47 -0700
Cc: triumphs@autox.team.net
>
>In article <199510241528.IAA23887@scn.org>,
>bc620@scn.org (Ernest G. Janzen) wrote:
>> Perhaps; however burnt exhaust valves are most often caused by setting the
>> exhaust valve clearance too tight or by too lean a fuel mixture. 
>
>I check/reset the clearances once a year - they should be OK.
>Regretfully, I never made a note of which way the clearances went,
>however. I distinctly remember *some* of them increasing due to rocker
>shaft wear. 
>

The recommendation I get from the "experts" is to set the valves on the 
loose side (increased clearance). That may not give maximum power but 
should be best for valve life - at least that makes sense to me.

>> A lean a fuel mixture may give good fuel economy but too lean a mixture
>> allows a lot of supper heated Oxygen to flow past a hot exhaust valve
>> burning the valve.
>
>Yes. But my PI system is definitely on the rich side. It registers
>rich when set up according to spec, and becomes even richer when
>engine vacuum decreases due to wear. 
>

You are fortunate in having a PI system, unfortunately they didn't import 
them to the US. (I didn't note your location originally and made the 
erroneously assumption that you had a carburetored system the way most of 
us in the US do.  Assumptions always seem to lead me to errors.)  I like 
your ideas of installing an oxygen sensor.  I wonder how hard is would be 
to install a PI system on my '74 TR6.

>
>But it is very easy to install an oxygen sensor (lambda sond) in the
>exhaust system to get a rich/lean indication brought to the dash.
>Just drill a hole and weld a nut over it as high up (i.e. hot) in 
>the exhaust system as possible. A standard unheated g.p. Bosch sensor
>may then be screwed right in. The voltage from the sensor (0 to 1V)
>will then indicate the rich/lean, with approx. 0.7V corresponding
>to stoichiometric.
>
>The information I've got indicate that the sensor will be very sensitive,
>and really only will be useful for indicating rich/lean. 
>
>I will be installing such a device real soon now, and can report my
>experiences later...
>
>Egil
>
>-- 
>Email: egilk@oslonett.no  Voice: +47 22523641/92022780 Fax: +47 22525899
>Snail: Egil Kvaleberg, Husebybakken 14A, 0379 Oslo, Norway
>URL:   http://www.oslonett.no/home/egilk/
>
>
Thanks for the information.  I look forward to your report on your 
experiences.

Ernest Janzen

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