Sooty No2 plug, Mk3 Spitfire

[1969Mk3Spitfire]

I’ve just removed the plugs and found that No2 cylinder is sooty. The other three all look fine. Plugs are NKG BP6ES. All gaps were fine.

I’ve recently noticed that choke/high idle feels a bit rough, hot engine idle is smooth. May or may not be relevant. Car otherwise seems to accelerate and run smoothly.

Found my 40+ year old Gunsons cylinder pressure tester in the loft and just about assured myself that cylinder pressure is ok before the aged rubber seal fell apart (one for the “I need a new one” list).

Also, adjusted the tappets but only a small tweak required on one or two of them, no real issues.

Any ideas? 

What are generally considered to be the best plugs for this revvy little engine?

 

[johny]

First try swopping plugs around then, if the same, swop over leads to see if the problems there... Unlikely to be mixture related as would affect more than one. 

[Pete Lewis]

there is a post about plug failures and NGK are one manufacturer that stopped glazing the centre insulator these take on waste fuel deposits from carb fueling 

and can cause misfires , there is no way of knowing if you have glazed or not  fuel injection doesnt need this protection so in modern cars its not a problem will try to search the plug posting 

many say bosch W78 or such are better  but  i always say make sure with our low HT coil voltages never fit plugs wit an R in the suffix  or you are looking for a problem to  emerge 

[Pete Lewis]

 

[NonMember]

19 minutes ago, Pete Lewis said:

there is a post about plug failures and NGK are one manufacturer that stopped glazing the centre insulator

This is particularly a problem on cars that run a bit rich (or only do short journeys). Strangely, my GT6 still suffers after being properly tuned, but neither the Vitesse nor the Spitifire have any problem with plug fouling. They even run happily on plugs the GT6 just won't tolerate.

[1969Mk3Spitfire]

I've put the miscreant plug into a different cylinder and I'll go for a ride just as soon as the drive is no longer blocked by the Disbeliever of the house.

Thanks for posting background links, Pete, but, as you wrote in one of the threads "after a few pages I lost the will to live".

There seems to be a lot of contradictory comments.

On a cross reference site, there's no mention of Bosch W78.  Google also suggests that it's hard to find.

Now very confused.......................

[daverclasper]

On 07/09/2021 at 10:22, johny said:

Unlikely to be mixture related as would affect more than one. 

Just interested. Could lower compression on say one cylinder, alter the burn/combustion?. I'm thinking, less bang, more unburnt fuel, showing a sootier plug?.

Dave

Edited September 8, 2021 by daverclasper

[johny]

yes theyve been checked in this case but if there were low compression it could make a big difference in the combustion performance of the cylinders affected...,

[Pete Lewis]

see reply in the dizzy thread  if the cam spindle is worn the gap at the points varies as it rotates  all dizzy need a squirt of oil down the base plate as the top bushes wear and are not engine pumped lubricated its a hands on service joby 

give the shaft a good shove if it moves its stuffed 

Pete

[sulzerman]

I bought a set of Bosch W78 plugs from the Green sparkplug company

https://www.gsparkplug.com/

 

[Pete Lewis]

2 hours ago, Mathew said:

Bosch W78 plugs from the Green sparkplug 

 

W78 again out of stock    the parts finder suggests WR78    that goes against all my experiences with any plug with an R in the suffix  on our limited HT 

Pete