Plug fouling

[jono]

My newly built TC keeps fouling plug 3 and occasionally plug 4 on cold starting.

It is running wasted spark ignition. The plugs are new NGK BP7ES and it has new silicone leads.

If I pull a lead and let it fire at the top of the plug it cures it and the engine runs and revs up beautifully which makes me think that the engine is intrinsically good (as should be expected). The ignition produces a nice fat spark.

I have not driven it yet so don't know the position on or during a good hot run. This appears to have developed since I set up the dellortos. When it is not fouled the engine does run very well with a lovely idle and the carbs do appear to be properly set up.

The cams are QED 360 and properly dialled in with vernier pulleys. The carbs were re jetted and choked according to the QED spec sheet for this state of tune.

What is the problem? Should I change to a different plug?

Cheers

Jon

[fatboyoz]

Jon,
My standard S4 with webers used to do the same thing. Cured it by changing to BP6ES.
Regards,
Colin.

[Mazzini]

Try BP6's they're better for day to day use, 7's are a bit hard, better for spirited fast road or track use.

[innesw]

My newly built TC keeps fouling plug 3 and occasionally plug 4
I have not driven it yet

Agra engineering who built my TC and rebuild many TCs every year say that if your just idling and adjusting the engine static in the garage then most TCs will foul up the 'plugs soonish when running on idle, without a good long drive.

However as its just 'plugs 3 and occasionally 4 you might need to make a slight adjustment with the balance.
They say a good long run usually sorts it out or will tell you if you need a slight change.
My car was very similar when I first got it going, living in Dundee I was lucky enough to pop round, put a set of fresh 'plugs in and they tuned the dellortos just that little bit extra. Now running perfect .

I use BP7ES NGK's aswell.

Innes
p.s. my balance issue was caused by me as I put air filters on the carbs but it was setup just on the trumpets.

[Mazzini]

Lots of threads on this forum regarding plugs, make a cup of tea and have a read, here's one to get you started - lotus-twincam-f39/plug-advice-please-t17686.html

[elanman999]

Jon,
As others have said try changing to a 6 grade of plug. Also try pumping the throttle less before starting. In this warmish weather my cars would only need half a pump.
Cheers
John

[jono]

Thanks guys,

The consensus seems to be a change to BPE6 plugs - I will try that.

Just for information what is the recommended starting procedure for twin dellortos?

Cheers

Jon

[terryp]

Use the choke - if old type pump jets - (vertical outlet)

As for webers - 1 to 3 pumps depending on weather - if new type pump jets - (horizontal outlet)

I've also always used BP6ES's

Terry

[foxoles]

On my '73 Europa Special with Dellortos starting procedure was 2 pumps of the throttle and then ignition.

[jono]

Thanks again chaps.

will report back with outcome.

Jon

[jono]

Thank for all your comments guys.

Re starting procedure - I have an electric fuel pump. Should I be switching the ignition on then pumping then starting or pumping first then ignition then start?

Jon

[PeterK]

Ignition on, so that fuel pump runs and fills float bowl.
When fuel pump stops 'ticking', bowl is full.
Pump throttle
Start car
Drive off with huge grin on face

[billwill]

Unless you have Dellortos carbs with downward pointing accellerator pump jets.

On those use the "Choke" don't pump as the fuel can get back into the trumpets and airbox.

The later jets pump sideways, down the throats towards the engine inlet valves.