One more about spark plugs

[dorchester]

I've read lot of advice and posts in this forum and still I can't make my mind about because nobody looks fully agreeing.
Here is my wish: finding the best spark plug for my early 1968 P5B coupé.
Never mind the price when it's a question of reliability, efficiency, durability and performance.

As I've found a garage able to adjust my SU carbs (I've seen a TR6 and a MGA in progress in it) I need to put everything on my side.

I like NGK brand.
So my question is: which is the best up-to-date and P5B compliant?

- BP5HS warmer
- BP6HS cooler

- or iridium ones like BPR6HIX or the like
Thank you for your wise advice and explanation if any.

[Phil Nottingham]

There is no difference between early and late P5B engines unless low compression heads have been fitted and in that case the warmer (hotter) plugs may be useful as fitted to early engines

What was and still is but more so is the fuel ie octane number, lead content and ethanol content plus driving style eg pootling around or high speed touring for the 2 extremes.

As such there is only one answer that suits your engine and driving style! 

I have used the warmer plugs specified by Rover from 1969 for approx. 80k miles. Never bothered with expensive fancy plugs as the standard lasts well over 12000 miles without bother. I have used unleaded for 14 years and E10 for 2

I used NGK's for years but the last lot I bought for our P4 and the Mini were rubbish and I now use Bosch W8BC and Champion L92YC is that equivalent = NGK BP5HS Unipart GSP 437

[lagain]

I could not get on with NGK in my P5b.
For years I have only used Unipart GSP 531
I find they suit her very well.

When refitting spark plugs always fit them carefully by hand, never use a plug spanner until you are certain that they are in correctly.

[dorchester]

Thank you both.
So no fancy then: I've ordered NGK BP5HS.

I like cruising without useless acceleration but if needed, no change in the heads AFAIAA, I'm filling up with 98 octane 5% ethanol (the best we could find here) and I've just bought NGK plugs from a reliable retailer who has already provided me with the electronic dizzy and the good NGK coil.
I've heard of Chinese NGK bad copies but I think the ones I've ordered are coming from a good source because of the pic of each box which is written in Japanese. Besides the price is decent but not at all the cheapest one.
Regarding the refitting it'll be done by the garage which will take in charge the SU carbs adjustment.
I'm crossing fingers and the rest...

%%

[lagain]

I think that I remember now what the problem was with the NGK plugs, the gap was 50 thou rather than the correct 25 thou, so it meant adjusting the electrode, which was not very satisfactory as the electrode was then at an angle.
Back in the day when a P5b was being serviced, the Rover dealer would have only used Lucas and Unipart.
The correct Unipart GSP 531 spark plug, with a 25 thou gap, is available from Roverpart of London, who list on ebay.

[dorchester]

Thank you but out of the mainland it's another story to find out any part or components.
I'm living in France and as you may know unfortunately silly custom taxes added to increasing shipping expenses are acting as a deterrent...
you can double the bill...