Fitting Platinum NGK Spark plugs

13th Feb 2007
I found whilst trying to tune the dual Weber IDF carbs that my cylinders where not all firing. I tracked this down to cylinder #1 spark plug not firing. I foolishly borrowed a plug from a friend only to find out when I decided that they all needed replacing that the plug I had used was a long reach plug. Initial horror of the piston hitting the spark plug was solved by doing a cylinder head pressure test. This still was mystifying as it did not explain why I had short reach Bosch plugs in long reach cylinders. I decided that I would have to investigate the cylinder heads further . I found an old C.K vernier gauge and bent the end of the tail of it over so that it was at a right angle to the depth gauge. With the plug out on cylinder #1 I was able to hook this under the threads and measure the distance to the top thread, this came about at between 16-17mm. Clearly I had bought Mexican 040 heads with long reach spark plug threads.

I noticed that whilst the plugs were in the car that the was a high degree of petrol in the emission from the exhaust. This inferred that the plugs were not burning all the petrol in the heads. Although this was possible caused by the short plugs in the longs threads I wanted to uprate the plugs to produce a better spark and decided that I would have to telephone NGK to find the correct plug to suit my engine.

I rang NGK and asked them about the different types of plugs that would fit my long reach thread engine heads. I asked about the quad,triple, Iridium and V type plugs. I explained that I wanted more spark in the cylinder head. The tech guy told me that the quad and triple electrode plugs did not always fire to every electrode and fired randomly, he went on to say that this would not provide a larger ignition over the cylinder. He suggested The V type plugs or Iridium or Platinum would be an option however there was no V type plugs that would fit my cylinders. He eventually suggested the NGK BP5EVX which where platinum plated long reach plugs.

I telephoned around my care tuning and accessories company's to no avail and eventually tracked them down on eBay.

The spark plugs arrived one week later and I was able to fit them quite quickly, however during fitting process I broke one of the stainless spark leads that I had paid over £50 for some years earlier . I was amazed to see how poorly they where constructed and that they were not well made. I removed the metal sleeve from the rubber spark plug cover and checked the end of the lead the centre of the lead was not broken and it looked as if it had never been soldered to the metal sleeve. I re crimped the sleeve back on leaving the centre lead touching the sleeve as it was on the other leads. I replaced the rubber sleeve using washing up solution. After washing and drying the lead to remove the washing up liquid from the end I re-fitted it and fired up the engine.

The engine fired up and I instantly noticed that the fuel residue in the exhausts had disappeared. It was clear that the carburetors still needed tuning and I left this to another day.

Parts Used
4 x NGK BP5EVX Platinum Spark Plugs.