Lotus Elan

Spark plug recommendation for cold starting problem

PostPost by: JohnMorin » Sun Mar 03, 2024 11:46 am

Hi

What are people's thoughts on the best spark plug for road use on a mildly tweaked twin cam, just a gas flowed head and running on Dellortos. At the moment I have Champion RN7YCC, which is what I used to use in the 70's and 80's, I had a small supply left over from then. The car is difficult to start when cold taking many turns of the key before it fires up, starts first time when warm though. I had a bad experience with NGK on my driving school car where although they were the recommended plug they wouldn't last 12,000 miles which was the recommended change interval, fitting the Champions sorted the problem.

I'm using Shell V Power petrol at the moment and my starting procedure is full choke and no throttle.

Ideas anyone?

Thanks

John
1969 Elan S4 FHC, purchased in 1978, now with a big valve engine.
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PostPost by: nmauduit » Sun Mar 03, 2024 2:21 pm

if all else is in good condition I would suppose the cold start difficulties are here attributed to sparks getting somewhat clogged from not being able to self-clean during operation: a hotter plug (higher number for Champion) would go in that direction.

For my S4 I run NGK spark plugs: I use a hotter set for street and a colder set for track days. Before returning to open roads I swap the plugs immediately as if one is not careful to rev the engine enough they may foul quickly (e.g. in congested traffic). nb: with NGK a hotter spark is a lower number (I use 7 for track and 6 for street). With clean plugs the car would start the same, but a difference may result of the type of previous use.

There are of course other possible causes of poor starting (esp. empty fuel bowl after a long period of rest - since I have now installed an electrical fuel pump I prime the carbs before starting and give a single press of the pedal, but before I would open the carbs to fill manually the bowls so as to avoid running the starter till they are primed).
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PostPost by: mark030358 » Sun Mar 03, 2024 3:12 pm

Hi,
I would think you need an electric pump to prime the carbs, as if left the fuel evaporates. I fitted because it would almost flatten the battery before it fired.

cheers
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PostPost by: JohnMorin » Sun Mar 03, 2024 4:14 pm

Thanks

I should have mentioned I do have an electric pump (Huco puller) and you can hear it prime the carbs when the ignition is switched on, I wait for that to finish before attempting to start.

John
1969 Elan S4 FHC, purchased in 1978, now with a big valve engine.
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PostPost by: 512BB » Sun Mar 03, 2024 8:53 pm

'my starting procedure is full choke and no throttle'

In over 40 years of driving Elans, I have never once used the choke to start, and that is with cars fitted with both Weber, but mainly Dellorto carbs, including in winter, when a Sprint was my every day car way back when.

Three or four presses of the loud pedal from cold, when it fires, slight blips of the pedal and away she goes.

Why don't you try that John.

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PostPost by: englishmaninwales » Sun Mar 03, 2024 11:27 pm

I can remember my father rescuing us with our stranded Lotus Cortina in 1966 following my mother trying to cold start it using the choke! His words are in my ears every time I start my Elan!
Last edited by englishmaninwales on Sun Mar 03, 2024 11:31 pm, edited 1 time in total.
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PostPost by: englishmaninwales » Sun Mar 03, 2024 11:30 pm

Double post
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PostPost by: TonyA » Sun Mar 03, 2024 11:58 pm

I wasted a year struggling with cold srarting on my plus2 S130. Then I did four things: installed a modern starter motor, (I recommend Wosp), changed the spark plugs from NGK BP7ES to hotter (= better self cleaning without thrashing) BP6ES, sorted out the oil leaks on the inner edges of the cam cover that got into the plugs and finally, I mustered the courage to use the choke. !

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PostPost by: rgh0 » Mon Mar 04, 2024 2:05 am

If you like Champion then use N9Y for road use the 7's are too cold and really for track use or continuous high speed driving

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PostPost by: Dellortofan » Thu Mar 07, 2024 3:28 pm

I go with the current OE manufacturers, even vw have gone to NGK.
Always seemed to be good for a wider range.
bosch nowadays are low quality. Russia and India made?!
A petrol transit we used as a towbarge misfired and stopped. 3 of the 4 champion plugs had snapped through the insulator.
I've not seen any for sale for ages.
Even plug quality with accuracy has moved on.
The cold start method of pumping mentioned is decades proven.
Less choke =less bore wear.
Why F. Inj engines last longer.
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PostPost by: Lotus54 » Thu Mar 07, 2024 3:39 pm

I would argue that using ‘choke’ (actually enrichener) for a minute when starting would result in a lot easier life on bore/rings that blasting a bunch of raw fuel down the cylinder.

Getting idle mixture right and still having good progression can be a little challenging for earlier DCOEs (well, in my experience anyway). So idling could dirty up the sparking plugs.

All the suggestions of a bit hotter one seem good to me, even the manual recommends so for the federal cars. I like to take a look and see how they are working in my particular engine/application. On my dirt bikes, I almost always run hotter than recemmended, since I run at idle/off idle a LOT and rarely run them hard (I do not ride fast anymore). This has worked really well for me, and the porcelain shows a nice temperature.

The ‘IX’ NGKs work well for me in other applications. I only recently got another Twincam car, and it has been decades since I owned one and do not remember now what I used. I do remember not having the greatest results from Champion back then and better with NGK.
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