Spark Plugs

[Scooterman]

Before the season I looked at all areas where we could squeeze a few bhp out of the old girl. One area I researched on here was spark plugs and I read that Denso Iridium IWF27 plugs were the ones to have, offering up to 2hp to poorly set up engines. However, I ran them at Oulton and I cooked two coils and set of points, the car also spent most of the weekend running on one cylinder and when it was on two it sounded rough. Switching back to NGK's for Croft seemed to solve the problem, does anyone know why this might be and are the Iridium plugs the ones to have? Thanks, Adam.

[Nick Roads]

I have run them with Lumenition for a few years. Strangely I was having problems at Outlon with misfiring and an engine at low revs on 1 cylinder. Swapped everything other than the driver and could not trace the problem.

No expert but do not think a spark plug can cook a coil?

[Simon Crook]

We had an issue with a bad batch Adam, engine kept going on one, sent the batch back and they replaced them and all was good, no issue after that

[Scooterman]

Thanks Simon/Nick

If the spark plug fault causes the car to run continuously on one cylinder, surely one side of the coil will be cooked? Certainly the scorch marks on the coils were consistent with that. I purchased the Denso's from ebay around 6 weeks ago, fairly sure I wont get a refund now. They cost over £20 for a pair, I bought 4 NGK's for £8. Do they make a difference? 

[naughtybear]

do you use those metal bands to fix the coil to the bracket - as we did on the orange car at Mallory last year and the plug leads were arcing down to that bracket causing scorch marks!

[Sean]

As one of the plugs in a 2cv engine fires backwards ie the spark goes from side electrode to centre, Im always suspicious of claims for special electrodes in our engines. Yellow accel coils will burn through HT boots and loves to short out through the metal fixing bands especially in high humidity and rain. It also highlights any problems with the HT lead.