Spark plug keeps failing

[andyamf]

hello,
i have a spitfire with a 2.5 six, i didn't build the engine but i know it was used for hill climbs so i assume it is in a higher state of tune, with triple twin choke webers.
it idles well, and accelerates smoothly.
the problem is since i put the engine in the number 1 spark plug keeps failing.
the car is driven once a week or so, and is never thrashed, just driven normally.
any ideas?
thanks in advance
andy

[Steve Cureton]

How often does it fail and what make of plug is it? If it's a Champion then try any other brand.

[Clive]

possibly it may have "harder" (is that the right term?) plugs. Try NGK BP6ES (def NOT RES version)
In what way is it failing? sooting/oiling up??

[andyamf]

it is running ngk bp6es, i also tried the champion ones.
when it fails it missfires, plug looks the same colour as the rest.

[Nick Jones]

Are they very black and sooty?  Having this issue with NGK BP6ES in 2.5PI and the problem seems to be overfuelling and the resulting wet carbon deposits causing the insulator to become conducting.  Have killed two plugs (new) so far and they look just the same as the others.....  Could try going to BP5ES (hotter) which will reduce fouling but could cause trouble with detonation (not at all good) at full chat.

Pics might help...

Nick

[Glenn]

I had a similar problem on my PI, and the advice I got was to change to Denso plugs.  They are cheaper too!

[GTRoger]

cliftyhanger wrote:

possibly it may have "harder" (is that the right term?) plugs. Try NGK BP6ES (def NOT RES version)
In what way is it failing? sooting/oiling up??

What's wrong with BPR6ES?  :-/

[James]

BPR just have a resistor in them— I have to use them in my car because of all the electrickery it has on it. Shouldn't make a difference on a normal car.

[TRTOM2498]

I run NGK BP6ES in my TR6 PI without any issues.  Accelerates cleanly from 1000-6000rpm, and done several thousand miles on them.

As per Nick, a picture would help here.

Cheers

[GTRoger]

jcarruthers wrote:

BPR just have a resistor in them— I have to use them in my car because of all the electrickery it has on it. Shouldn't make a difference on a normal car.

Exactly! That's why I'm wondering why they shouldn't be used. It's exactly the same plug, only having the resistor as an extra.  

[Dicky Blighter]

Sure it's the plug failing and not the lead?
Easy to check by swapping a couple of leads over

[andyamf]

yes, number one was spitting back through the carb, changed plug 1 and 2 then 2 started doing it.
def the plug, anyway have found a local place who do ngk's at 1.15 quid, will buy a set, and keep on troubleshooting

[Velocita Rosso]

Id be interested in how its failing.(and why no.1 all the time)
If its failing on the spark because of oiling etc then I would consider internals problems
However is it failing because of ceramic cracking eg heat and quick cooling cos of it being near air inlet or is it being knocked or caught etc?

[Toledo Man]

I swear by NGKs myself. All my cars have been running on them without any issues.