Lotus Elan and Lotus Elan Plus 2 Forums

On my rebuilt stock SE engine with Delortto carbs I started using NGK BP7ES plugs. After a long drive I checked the plug colour and found the centre electrode to be correct and the outer metal rim of the plug to be slightly sooty. I then did the same run using BP6ES plugs. This time the centre electrode was similar (grey/brown) but the outer rim was completely clean with no soot. Is it therefore better to stick with these plugs?
The engine idles and picks up with no hesitation so I assume the jetting, etc is fine.

BP6ES I have found best like you for a normal road twincam engine in normal mixed city / country road driving. BP7ES only really needed in a road car if doing lots of continuous high speed full throttle driving in places like German autobahns or the equivalent

cheers
Rohan

what plugs are folks using for hot (160 HP) street motors on the street and for track events? Currently using BP6ES

Eric
64 S1 Hart

Hello William

I am also now using BP6ES plugs in my tired Twin Cam and it runs a lot better than when I used BP7ES's.

My two old +2s both on Dellortos were definitely happier on BP6ES but the funny thing my current Elan with Strombergs prefers BP7ES, the BP6ES I had originally fitted becoming slightly over burnt.
I think it must be a case of fit and see.

Terry

My S4 SE with Strombergs, which has had some engine mods done by Oselli by a previous owner, came with BP5ES but kept fouling so after reviewing this forum I changed to 6's. Still was getting problems occasionally so had a regular routing of cleaning them. I met another owner at Brooklands one day and he suggested going back to 7's which is what is in the handbook.

I have been using 7's for several months now and they have been by a long way the best - no regular cleaning and engine has run fine hot and cold.



John

HampshireMush wrote:My S4 SE with Strombergs, which has had some engine mods done by Oselli by a previous owner, came with BP5ES but kept fouling so after reviewing this forum I changed to 6's. Still was getting problems occasionally so had a regular routing of cleaning them. I met another owner at Brooklands one day and he suggested going back to 7's which is what is in the handbook.

I have been using 7's for several months now and they have been by a long way the best - no regular cleaning and engine has run fine hot and cold.



John

There must have been something else at work there as BP5ES is a hotter plug than BP6 or BP7. If fouling was caused by too cold a plug then going to 6 or 7 would have made it worse. See NGK's explanation: http://www.ngk.com.au/spark-plugs/technical-information/heat-range-explanation

I wonder if there's some confusion between different makes. NGK heat range numbers run the opposite way from Champion, for example.
Champion N7Y is equivalent to NGK BP7ES (roughly), but a NGK 5 burns hotter, a Champion 5 burns colder.

Also, Stromberg engines run a bit hotter than Weber or Dellorto, explaining Terry's findings.