401 Ignition Coil

[dezelsky]

I recently had the misfortune of a failed ignition coil in my 401
(whilst travelling on the M25, of course). After the car was
recovered, as it was a Sunday I was unable to get a direct replacement
(Lucas B12 or suitable replica), but I did manage to scrounge a Lucas
Sports Coil as fitted to an Aceca Bristol, which seems to work
perfectly well. I have tried to verify the compatibility of the sports
coil as a replacement to the standard, but have been unable to find a
definitive answer. There are comments on other make sites suggesting
that the Lucas sports coil should not be used as a replacement to the
standard item. Does anyone on the forum have any thoughts on this? Is
the sports-coil likely to damage other parts of the ignition system or
is it actually a better alternative to the B12?

Paul

[brianjgkidd]

> > I fitted a high energy coil to my 405 a few years ago, with beneficial results - never any problem with misfiring. However, this type of coil may need to have a ballast resistor fitted, which reduces voltage to the coil of about 7 volts, lessening wear of contact points, etc.. But this may require the fitting of a modified starter solenoid to allow the ballast resistor to be by-passed to ensure full battery voltage to the coil during starter motor operation. This momentary voltage overload is acceptable, but continued operation without the protection of the ballast resistor is likely to lead to damage to the coil.

Regards,

Brian Kidd> > > > >

[Ashley James]

I thought I'd posted this but I'd caution against using sports coils
on old ignition systems with dynamo charging circuits. First they
take an amp or two more from an overworked dynamo and this might be
make or break on a cold night home in dark and rain, and the rise
time is much faster and this often causes arcing elsewhere than the
plug.

Mart, my business partner is an electronics engineer and he tells me
standard one is okay to 12-15000 rpm on a Bristol, so hopefully enough
for yours.

www.vintagemotorspares.co.uk for a cheap Lucas original.

Ash

[brianjgkidd]

> > Well, my 405 is fitted with an alternator. But there is no question in my mind of the benefits of the high energy coil - at least in my experience, including some quite arduous continental tours to Italy, where the ignition system performed perfectly, and never with a hint of a misfire.

Regards,

Brian Kidd> > > > >

[Richard]

Originally Posted by brianjgkidd

> > Well, my 405 is fitted with an alternator.

I would be interested to know which alternator you have fitted and what other modifications it required.
I have been considering replacing the dynamo on my 405 with an alternator but have postponed it for the present as not being worth the effort.
Richard

[brianjgkidd]

> My 405 is still positive earth, and has been been fitted for over 30 years with a Lucas 11AC alternator; in that time I have had one alternator failure, a seized rear bearing requiring me to spend 4 days in Orvieto (oh dear!) while it was fixed. My alternator installation has a Lucas 4TR voltage controller, a field isolating relay, a warning light contoller and an ammeter. These ancillary components should not be diifficult to source, but I found it difficult to source a suitable 11AC alternator for my son's early E-type Jaguar. In the end, we changed the polarity, and fitted a modern lightweight Nippondenso alternator.

If you want to fit a modern alternator, then you will have to change to a negative earth system - not difficult though you would need to check for any polarity sensitive components on your car. Other than that, packaging is likely to be the only issue - but certainly no problem on my installation.

Regards,

Brian Kidd> > > > > >

[brianjgkidd]

> I think we're going to have to agree to disagree on this one. I ran a Bristol 400 for
10 years with an entirely conventional ignition system - lovely car but, unless everything was on top line with the ignition system, it was prone to misfiring.

When I purchased a 405 30(!) years ago it was fitted with a Mobelec electonic system which, whilst this overcame the misfiring problem, was not entirely reliable. Moreover, when I started classic car rallying such a system would clearly be frowned on by the rally scrutineers as non-original. So back to the conventional coil/CB system. But, once again, unless everything in the ignition system was A1, the occasional misfiring was possible. However, 8 years ago, on fitting a high energy coil with a ceramic ballast resistor - end of problems; never a misfire, reduced wear/pitting of the contact breaker points, absolutely no arcing at rotor arm. I set the plug gaps at ."025; cold starting is always excellent.

Each to his own, I suppose.

Regards,

Brian Kidd> > > > > >

[Bellerophon]

Most of the problems which seen to crop up are because the cars have worn
and are not to their original specification that they left the works in, and
instead of correcting the faults people change the set up. (several members
have been caught out by electronic ignition going dead on then and there was
nothing that they could do to get the car going)
I bought my 401 car in 1962, it had a sports coil fitted, and at the time I
raced and rallied the car and never had a problem with the ignition until 1995
when the coil failed when it became warm. I fitted a new sports coil and
have been running well ever since. (with no detrimental effects).
However, the question I ask is how many members look after their
distributor? That is clean it and all the wires, check and lubricate the balance weights
etc.
The thing you should remember is that the car was on the top line when it
left the works, and if it has been looked after it still should be, so you do
not need to modify it to make it run correctly.
My regards,
Bellerophon