Spark plugs, spark plugs, spar......

[jpmf]

Is it just me or am I doing something wrong?

Spark plugs don't seem to last the proverbial. Replaced Champions RY12YC, that had hardly done 1000 miles, to Autolite AP85 and they have hardly done 500. Pig to start, running on 5 or 6 with no power on acceleration but you could feel the surge as other cylinders tried to join in the craic.

It ran great when I first fitted the Autolites and then slowly got worse so I replaced any that were sooted up due to inactivity (3 no.) with some old NGK BP5S I had in the boot, we now have 8 at the party. And I also went back to my old leads which were replaced when I fitted headers (could be leads).

I'm setting the gap at 35 thou, is this too much or not enough? Am I doing something else to 'cook' the plugs, too lean, too rich? Any that were not black were showing a hint of brown, and there is a mix on either side and not all on one bank.

I now have two new sets of plugs, Denso W14pru V groove (very smart!) and Bosch 125TR6, any suggestions on which ones I should try and destroy first?

And I've also had an issue with the vac advance canister not living up to expectations (even though it's new). I am now coming directly off the back of the carb, constant manifold vac, but it still won't 'wake up' so I have to dive in with a small allen key and adjust it until it works and then adjust again for correct advance. Does this need lube?

[Keith]

Technical section, technical section, technical section......

Here's a good thread on plugs:

http://www.joc.org.uk/phpBB2/viewtopic.php?f=4&t=20201" onclick="window.open(this.href);return false;

[alanB]

Could be carb or ignition problems ?

I'd be inclinded to keep trying the easy swaps:

Maybe a weak spark ? Have you a spare coil to try ? Possibly a ballast resistor being excessively resistive ?

Clean out the air filter ?

Sticky choke ? Maybe some carb cleaner ?

I do a lot of short runs in the Interceptor and find a mix of 12s and 14s works for me

[Philip Lochner]

Could be carb or ignition problems ?

I put my money on excessively rich running. There is nothing that kills plugs quicker than over fuelling.

If you still have the Carter Thermoquad, chances are that those two little X-rings in the carb has gone causing fuel to spill over from the float chambers into the carb primary barrels. I'm using suitably sized regular O-rings without trouble.

[jpmf]

Could be carb or ignition problems ?

I put my money on excessively rich running. There is nothing that kills plugs quicker than over fuelling.

If you still have the Carter Thermoquad, chances are that those two little X-rings in the carb has gone causing fuel to spill over from the float chambers into the carb primary barrels. I'm using suitably sized regular O-rings without trouble.

Philip,

I will look at that as I get a lot of spitting back through the carb, and the car surges as I accelerate as more cylinders fire which suggests that the excess fuel is getting burnt, and the plugs come to life.

[Philip Lochner]

as I get a lot of spitting back through the carb, and the car surges as I accelerate as more cylinders fire which suggests that the excess fuel is getting burnt, and the plugs come to life.

That also sounds like unstable ignition, so don't ignore ignition related causes.

[jpmf]

as I get a lot of spitting back through the carb, and the car surges as I accelerate as more cylinders fire which suggests that the excess fuel is getting burnt, and the plugs come to life.

That also sounds like unstable ignition, so don't ignore ignition related causes.

I haven't ruled out ignition, but will investigate all options, thanks.