Spark plugs for a Lwt?

[LarryH57]

I have used NGK spark plugs on my Lwt for years but with Powerspark electronic ignition fitted which is best, as I have always avoided those with an R in the title which I understand is R for resister or resisted? But what does that do for the ignition?

So BP5ES or BPR5ES?

[fv1609]

Larry it depends whether you have resistive leads or not. People often fight shy of having resistance in the ignition system for fear of losing HT voltage. But the current of the HT is very low & the voltage drop of having resistive plugs or resistive leads or screw on resistors is negligible.

The effect of having resistance is to help reduce erosion on the sparking plug electrodes & the rotor arm/distributor poles. Apart from that resistance helps reduce radio frequency interference. I don't know if the law has changed or faded into oblivion but it used to be a legal requirement to incorporate resistance into the ignition HT system.