----- Original Message -----
From: "Dave Massey" <105671.471@compuserve.com>
To: "StevesTR" <StevesTR@veroquest.com>
Cc: <triumphs@autox.team.net>
Sent: Sunday, June 27, 2004 5:58 PM
Subject: TR6 Spark Plug Issue
> Message text written by "StevesTR"
> >Any spark experts out there? I am left guessing on this one: Everything
> on this TR6 is rebuilt, there are no vacuum leaks that I can find. If I
> put in a new set of spark plugs, my 74 TR6 will run perfectly for about
> 500 or so miles. After that it starts missing at low RPM when under
> load. <
>
> Have you checked the gap. The TR6 plugs should be gapped to .025 which is
> quite a bit tighter than what is typical of modern cars and you plugs may
> come factory gapped at .040 or greater. The TR6 coil does not put out
> enough voltage for that gap under all conditions (Under load at low RPM's,
> for example).
>
> I had similar problems and found my plug gaps were on the order of .035.
> Reseting the gap cured all problems.
>
> Dave Massey
> 71 TR6
Steve, Dave and others-
If you are running the Crane ignition box and a Sport coil, the plug gap
should be somewhere around .035", not the stock .025". Ignition wires may be
the culprit here. Check your wires, you should get around 7000 Ohms per
lineal foot of resistance as a rule of thumb. There are many wires
distributed out there that do not have enough resistance to give good
performance. Check the ignition wire routing to be sure there are no crossed
wires. Also check your dizzy cap and rotor for premature wear. You may want
to check the resistance of a new set of plugs to the old ones that you are
replacing. If the resistance is different, there is something going on with
the heat cycling that is changing the plug's resistance. If that are the
same, then the problem lies elsewhere. When was the last time you retorqued
the intake and exhaust manifolds? You may have a lean condition attributing
to your problem.
I have run Champion plugs gapped at .035" in my TR6 with a Crane
ignition & Sport coil for many miles without a problem. Good luck and let us
know what you find...
Tim Hutchisen
80 TR7 Spider (now for sale) will be Concoursed at VTR 2004
71 TR6 staying home
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