Sparking Plugs

[B.P.Bird]

What sparking plugs are Members using in their Ace Bristols ? I had some Champion Z9Y, but this is what happened to them:





The other five had started down the same road with the porcelain coming uncrimped from the metal base:





I have found NGK tend to wet too easily on start up so I have gone back to some old, but serviced, KLG TENL100:





However I have very few KLG left on the shelf and a permanent solution is needed. The best 'plugs I ever used were KLG PTENL80, the P signifying platinum - anything like this available nowadays ?

[AC Ace Bristol]

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Barrie

I run BEX333 on NGK C7HSA and have since  2002 when I found it impossible to locate stock of K-L-G  TEN L  80 or  K-L-G  Ten L 100's .
I Have a dozen or so second hand ones ,which came with BEX when I imported her from Seattle in Sept 2000, not sure how  or where to get them tested.


Never had a problem with the NGK7's ,  ( C8s are a  colderplug )   However I know a fair few racing will warm up and change temperature range plugs according to conditions.


In  the 1970's  I  used to experience heat range  problems and serious fouling of plugs with both  the Lotus Twin Cam and the  all steel  1800 Cosworth BDB especially in heavy traffic in London.


Not sure if my comments help,    Barrie  my S/H K-L-Gs are available  to you if they could be servicable .

Keith

[Jim A]

It looks like your plug wrench is one with vinyl tape wrapped around a swivel or u-joint.
I wonder if every Bristol engine owner has one.

[B.P.Bird]

Keith,
Thank you I will explore the NGK C7HSA and C8HSA and their iridium equivalents CR7HIX and CR8HIX. Thanks for the offer of the used PTENL80, however, even when pressure tested satisfactorily, used plugs often do not perform well.
Jim,
Not sure if your comment is tongue in cheek - this is the standard Bristol plug spanner, supplied by A.C. with every Bristol engined car and, yes, the UJ is taped up which gives it a little stiffness and makes finding the plug 'ole easier (the more raffish amongst the audience will realise that this sentence reads better if the word 'plug' is omitted......)
Barrie

[AC Ace Bristol]

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Barrie

 About 8 or 9 years ago I considered  testing the NGK Iridium 1X equivelent to the   NGK  CR7HSA,  but with such a difference in price decided to stay put and check / replace all six plugs more regularly.  BEX333 has compression ratio of 10.2 : 1  occassionaly on steep mountianous  gradiants have  experienced Pinking , then I've manually retarded the ignition which has solved the problem.
The NGK C7HSA have shown very little wear and the gap seldom needs much attention.

I believe NGK plugs were discussed in depth on our Forum some 7, 8 or 9 years ago, Could be worth checking back in the Forum Archives,

If you do go the Iridium route, Can you please post  a report. ..

Has anyone else used the  NGK range of   Iridium plugs ?

Keith
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[B.P.Bird]

Keith,
Yes the discussion you refer to is still on the Forum:

https://www.acownersclub.co.uk/forum/index.php?topic=1227.msg11398#msg11398

The references to fitting longer reach plugs should be regarded with great suspicion, but the rest of the information is useful. So far as iridium tipped sparking plugs are concerned they do give a noticeable improvement in performance on the standard EFi 302 engine used in our Mk. IV CRS and I think that is a generally accepted view amongst owners. It is on that basis that I elected to try NGK CR7HIX: Expensive at £50 for a Bristol engine set and their increased life is hardly relevant in our old cars, but if they work as well as in the 302 it will be worth it. The increased life seems to be universally endorsed by users, but the performance advantage gives rise to more diverse opinions. NGK do claim improvements, but not large increases in power and this is as one would expect.
One depressing facet of all this is the limited choice we face in the area of sparking plugs. The two manufacturers who innovated and improved over many decades and who both produced excellent plugs in general and in particular plugs that worked well in the Bristol are no longer available - Lodge and KLG. As you see from this thread only one manufacturer has been suggested.
I will let you know how it goes
Barrie

[AC Ace Bristol]

.
Barrie

As our spark plugs are same size as those fitted to  modern high performance motor bikes,  Could be worth while investigating availability and suitability.

Just an  idea, nothing ventured ,nothing gained.

Keith

[TTM]

Good evening,

In my limited experience, Iridum spark plugs improve idle stability and quietness and engine smoothness at any load, though that was with an engine quite a bit more modern than the Bristol engine. I am really curious about what you will find Barrie as when I refreshed the ignition set up on the Ace I wondered if I should not also try some "exotic" plugs over the NGK C7HSA.

On a side note, would there be any advantage to have the spark plug tip clearly protrude into the combustion chamber like on most modern engines instead of sitting a few mm below the hole?

[B.P.Bird]

Progress report: I fitted the NGK CR7HIX and ran 40 miles so far. As I said previously the NGK C7HSA and C8HSA tended to wet on start up. The iridium tipped version has not done this so that is the first advantage. There is a noticeable improvement in gaining revs above 3,000 rpm and a noticeable improvement in torque below this figure. Of course these are subjective opinions and back to back stopwatch tests would paint the true picture. Nevertheless I think the improvements are real and this is the second advantage. The third point may or may not be an advantage, but it is real - the exhaust note has changed, noticeably a sharper rasp. I had a chat with Tim Green at The Green Spark Plug Company,

http://www.gsparkplug.com/ignition/spark-plugs

and he had heard reports from several owners of different cars that the iridium plugs had altered their exhaust note. More importantly he solved the mystery of what had caused the Champion sparking plug failures which started this thread. The Champion Z9Y should not be fitted to the Bristol engine. This is a low performance plug which will not stand higher compression ratios.
With regard to the question from Thomas about the shrouded position of the sparking plug electrodes, in the Bristol, I can only say that is a deliberate part of the design. I wonder if it came from Bristol Aero Engine practice or was it also part of the original BMW design ? We have all seen the the great increase in power from the Bristol engine in what passes for Historic Racing nowadays, perhaps they have unshrrouded the sparking plug, does anyone know ?
For what its worth I intend to leave the sparking plug where Bristol put it.

[TTM]

Good morning,
 
I followed in Barrie's footsteps and fitted a set of NGK CR7HIX in replacement of the NGK C7HSA. After a 60 mile drive, I can say that the results are consistent with my past experience with Iridium plugs of another brand on a quite different, all alloy engine. The engine runs a little more smoothly, sounds a little quieter and seems to have a little more mid range. The engine also reacts a little more swiftly to small throttle inputs. Although this is of course all a bit subjective, I would think that the gains in overall refinement are worth it. I must add that I use a twin point distributor and I am tempted to think that it is probably making better use of such modern spark plugs than the original single point Lucas distributor would...?

[AC Ace Bristol]

Barrie

Had a long chat with Mark Morgan at The Bentley Drivers Club meeting at Silverstone yesterday.

Note he has upgraded  to irridium plugs and confirmed that His Ace Bristol (BEX284) is running smoother and more responsive, also noted the engine/ exhaust note has changed,  Mind you it is still many decibels quieter than many road going Ace Bristols, could be down to the larger than nornal silencer keeping the passenger seat and floorpan  warm.

Keith
 

[B.P.Bird]

Keith & Thomas,
I have now done a fair amount of starting and stopping and enthusiastic running with the CR7HIX and can say that my first favourable impressions have been continued. LM 5000 is more prone to plug wetting than the standard 100D2, having bigger jets and bigger throttle bodies. They were, after all, only interested in flat out running at le Mans and Goodwood, however with the iridium 'plugs even slow driving in traffic and start ups from cold have not caused any sparking plug removals for cleaning - a clear road and some rpm is all that is needed to clear the old things throat. This has never been the case before, once a 'plug had wetted it had to be removed for cleaning; no amount of thrashing would get it to work.

[TTM]

Barrie,

Well done, and thank you for sharing with us in the first place about this worthwhile upgrade.
I am also quite pleased with the subtle improvements those plugs have brought on my 100D2 engine, even if it is probably closer to standard spec than yours.