[TR] TR3 coil question

[Kinderlehrer]

Hi Andrew,

My understanding is that the TR3 uses a non-ballasted 3.5 ohm coil, but
that's stock. But, if you are frying coils, I would suspect the voltage
regulator. You don't say if you have a generator or upgraded to an
alternator, but in either case, I would guess that if the voltage isn't
being controlled, it could result in an excess of power, particularly at
high revs, and the symptoms you are experiencing.

Just my guess,

Bob

 

From: Triumphs [mailto:triumphs-bounces at autox.team.net] On Behalf Of Andrew
Uprichard
Sent: Thursday, September 17, 2015 1:41 PM
To: triumphs at autox.team.net
Subject: [TR] TR3 coil question

 

I recently finished the restoration of a '57 small-mouth with a number of
upgrades / modifications including oversize pistons, ported head, lightened
flywheel, SU HS6 carbs with long intake manifold, and a 1,2,3 distributor.

 

The car runs great, but I seem to be frying coils, usually after pushing the
revs.

 

The first time it happened, I called 1,2,3 and they reminded me I had to use
a coil with more than 1.0 (and ideally more than 1.5) ohms resistance and no
external ballast.  I tried a regular Lucas coil and all was well until I
took the car to a rolling road yesterday and we ran it up to 5500 rpm.  (By
the way, the carburetion was fine  throughout the rev range, so I don't
think this is a fuel issue).  The car performed well on the dyno, but on the
way home started to backfire on acceleration, the same symptoms I have had
twice before and have been "cured" by replacing the coil.

 

This time I have ordered a Bosch Blue, 3.5 ohm coil, as recommended by
1,2,3.

 

If it happens again, I think I will revert to a standard points or Pertronix
set-up and see how the car runs, but I was wondering if anyone had had a
similar experience or might have any suggestions.

 

Andrew Uprichard

 

P.S.  The one thing we did observe at the rolling road was there was too
much advance:  around 10 degrees at idle and 35 degrees (25 added by the
!,2,3 distributor) at 4000 rpm. Although the car wasn't pinging, it did
flatten out around 4500 where one might have expected more power.  I can't
see how too much advance could be a culprit, but I am open to any thoughts.

 

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