I have an 85 xj6 series III 4.2L with weak spark going to plugs.

What is the best distributor cap to prevent arcing to the block?

At night, with any old standard cap you can see blue arcing between the cap wall and the block.

I want to get a better quality heavy duty distributor cap to contain the high voltage and prevent leaking.

Thanks in advance,
BrightonRay

 

I have a petronix in my 85 and I love how well it performs.

 

I've had best luck using Lucas caps and rotors. High grade stuff.....at least they used to be. Haven't had to buy any in the last few years.

Cheers
DD

 

one time at a Jaguar Club Meet I was told the Blue caps are better than the Black ones.

I am not sure if that was a joke or the truth, but I was given (FREE) a Blue one to try, I installed it and frankly I never noticed any difference, other than it's been like 16 years since I installed it.

 

How are your leads? Seems strange that the spark is strong at the cap but weak at the plugs.