What spark plugs do you fit in your 1500cc Dolomite?

[Richard the old one]

Yesterday I looked in edition 2 of the Official Triumph Dolomite Handbook that came with the car to see what new spark plugs I should purchase. This document gave the plug type as being Champion N9Y so I purchased a set of NGK BP6ES.

It was only when I came to put them away that I discovered in the past I have fitted NGK BP5ES so I have been investigating.

I found an edition 6 of the Official Triumph Dolomite Handbook and this gives the plugs as being Champion N12Y. This is also the type indicated in the 1984 edition of the Official Triumph Dolomite parts catalogue for 1976b onwards cars.

When I looked at the various Haynes manuals that I have the 1984 edition states it should be a N12Y but more interestingly in a 1978 edition it states that up to engine number 25083 it should be a N9Y and after that it should be the N12Y

I also looked on the NGK web site and this gives the BP5ES as being the spark plug that is applicable for a 1976 to 1980 1500 dolomite.

I do not know and can’t find what the difference is between a BP5ES and a BP6ES. Can anyone advise as a matter of interest.

[Mad Mart]

This may be of use Richard...

[dollyman]

Back in the day Richard i would fit what was in stock and never had a problem. I have three Triumphs and all have the BP6ES in them One is slightly hotter than the BP5ES.

Tony.

[Richard the old one]

Many thanks for the quick responses.

[GTS290N]

I know that 5 is hotter than 6.
But what does hotter mean?
What is it that is hotter?

[SiC]

These pages explain it reasonably well:
https://www.ngk.com.au/technical_info/heat-range/
https://www.denso.com/global/en/product ... heatrange/

[SiC]

I believe a cooler plug can help when using fuel with higher ethanol content too.

[soe8m]

As with myself, better too hot than too cool.

Jeroen