Which spark plugs?

Hello all,

The Rover Repair Operation Manual states that the correct set of spark plugs for my vehicle (P6 2000 TC) is the N6Y. However, the sticker under the bonnet reads N7Y only. Which one is correct? I've got a set of NGK equivalent to the N7Y fitted at the moment and I wonder if the pinking problem I am having could be related to that?
I think that N6Y's were superseded (or at least "replaced by") N7Y. I also think the early 2000TC decals did specify N6Y's, but the later models had the decal specifying N7Y's (certainly the old UK J reg 2000TC we scrapped had N7Y's on the decal)

Maybe someone could confirm/agree/partially agree/totally deny... this?


Well-Known Member
I would agree with that, the N6Y's were superceded by N7Y's for all TC variants, in the same way that V8's had the original L87Y's replaced by L92Y's, but early cars still had the underbonnet label specifying L87Y, as the labels were never changed.
Interestingly I've just checked the Champion website, and the N6Y will be a colder plug than the N7Y, a hotter plug will prevent fouling but will be more prone to pinking. So maybe they went to the N7Y to combat plug fouling on the TC. You could try a set on N6Y's and see if it improves the pinking problem, it's not going to damage the engine, so it's just the cost of the plugs.
The recommendation was changed at some stage due to plug fouling in the 2000 TC motor. If N6Y's work for you, then go with them. Since N7Y's are not working for you then N6Y's may be worth a try. What thermostat are you running? You may find that N6Y's with a 180 degree thermostat, which is a common thermostat to use in a 2000 motor may help solve the problem. You may want to try fine wire iridium plug, BPR6EIX. Some people who run high energy ignitions have reported good results with these plugs, with less plug fouling issues. The original thermostat recommendation was 170 degrees. These are hard to come by these days. On my Rover 2000 automatic, in Australia I run a 160 degree thermostat. My 2000 TC which is in upstate NY, I run at 180 degrees. I could hardly get it on the gauge at 160 degrees and the plugs tended to foul. On the 2000 automatic, if I run it at 180 degrees, I get overrun issues.

So experiment a bit, and work out what works for you motor. They all have a bit of a personality, depending on your driving style, ring and bore condition, climate, and ignition system. I like high energy coils, set up with points. I have done a lot of miles with no problems this way. However the coil that I like I can only get in Australia, the Bosch GT40. You might be able to get it in the UK, you cannot in USA, as apparently there is a trademark problem

Thanks a lot for your insights.

Interesting, I thought the N7Y would be colder then the N6Y... so it is actually the opposite! As a matter of fact, my car started pinking after I went from the N6Ys to the N7Ys.

I've heard about the iridium plugs before. Are they actually better in reducing fouling?

By the way, I don't know which thermostat is fitted in my car. How do I find out?

As for the coil, will the GT40 work alright in a ballasted system? It seems that they are 12 volts?


If you have a ballast resistor then you need a GT40 R coil. The R being for resistor.

There are a few ways to work out which thermostat you have. The first one is to take it out and it will be marked on it somewhere in C or F. The other way is to start your car up when cold. When you feel the temperature change in the top radiator tank, have a look at the temp gauge and see what it reads. This should give you a fair idea. You can also measure it with and infra red sensor type hand held thermometer.

With NGK plugs the higher the number the cooler the plugs. Most other brands the higher the number the warmer the plug.

In this case, I have commited a serious mistake. I thought that the numbers would be equivalent, so I was using BP6ES in place of N6Y, when actualy I should be using BP8ES. I guess the same would apply to the iridium plugs, I need the BPR8EIX probably.

As for the Bosch GT40R, so far I had no joy in sourcing it. Does anyone know any supplier?

If your using a very hot plug I could imagine that triggering pinking. Probably best invest in a couple of sets across the heat range and see what works for you. Then move to the iridium equivalent at next plug change.

I am quite happy to accept the notion of different plugs for different engines. They are old enough now to have developed their own individual quirks through things like where and how much gunge build up you have in the cooling system, what thermostat you are running and how effective the rad is, not to mention what sort of climatic conditions you have where you are. For similar reasons it was once common to use a differnet grade plug in the winter to the summer.


a little update:

1) Changed spark plugs - Iridum BPR8EIX (equivalent to N6Y)
2) Flushed and changed coolant
3) Retarded ignition as much as I could
4) Put BG44K to try to clean combustion chamber

The car is still pinking although all those attempts. I still haven't tried the thermostat, advance unit and the coil change.

Any other suggestions?


Going back to the original noise, you said that it only happens under load when the engine is hot. Is it showing good oil pressure when hot at idle ?
The gauge shows slightly bellow 50 when at iddle. When running it goes up a fraction.

Just thought it would be good to mention: I have noticed that one of the rubber tips on the advance pipe is cracked, so I have order a replacement.

By the way, does any of you know how to test the advance vacuum unit?


Hi Andre. To test the vacuum advance, first take the distributor cap off. Then suck hard on the small bore pipe from the inlet manifold to the advance unit. You should then be able to see the base plate of the distributor (that carries the points and capacitor) rotate to and fro. You should also be able to rotate it by hand and watch it spring back to the original position - that's the centrifugal advance. If it is sticky then simply unscrew it and take it out of the distributor. Underneath are a couple of flyweights pivoted on pegs. This arrangement should be clean and dry (not lubricated) and is likely to need a bit of a clean up. You'll disconnect the vacuum advance in the process which would then allow you to remove it if you had to change it.

Getting this right will markedly affect the performance of the engine and also its propensity for pinking. You'll need to reset the points gap, dwell and timing after.



Well-Known Member
The vacuum advance is an economy device, advancing the timing most when the throttles are closed and there is maximum suction, it will have little, if any, effect on pinking. The baseplate moves with vacuum advance, it stays still with centrifugal advance, in that case it's the rotor shaft that moves, advancing the timing that way. To check centrifugal advance you need to twist the rotor in the direction of rotation and see if it springs back.
Many thanks for the insights!

I have changed the coil to the Lucas sports one (40.000 volts) and the thermostat to the 74 degrees one. No joy...

I've tried to do the suction test. The base plate had a minimum movement. Also I noticed that there was a lot of air passing throught the pipe. I then decided to go for a drive with the pipe disconected - the pinking STOPED completelly! I guess that's because the innoperative advance was allowing the distrubutor to move more than it should?

Any thoughts on that? It is so good to be able to drive normally again without that annoying mettalic noise in my ear. However, I am a bit concerned: what are the inconveniences of driving with the vaccum unit disconected?