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MG MGB GT V8 Factory Originals Technical - Spark plugs

I'd like to get some information about spark-plugs including what are the symptoms typically of worn plugs or incorrectly set gaps or incorrect plugs. Also the different types and ratings of spark-plugs available.
Marc

Hi Marc,

Typically too cool a rating will foul, too hot a rating will burn. Excessive gap due to wear or erosion can cause poor starting or HT breakdown elsewhere in the system. I found I had to keep a new set in the car as every now and again, much less than the recommended 10k change intervals, which are themselves pretty conservative, it wouldn't start from cold. As this was usually when I needed to be elsewhere I put the new ones in and away we went, the plugs I took out were always in perfect physical condition. Not too long ago it happened when I had some time to diagnose just what was happening and I found that although I could get a timing light to flash when clipped onto the coil lead it didn't on any of the plug leads. Fitted the spare cap and again off we went. The old cap looked just fine - no cracking or tracking, but I'm wondering if that had been the problem all along - a marginal cap breaking down as the plugs got a little harder to fire. Time will tell.
Paul Hunt

What is a good standard plug to use? Im running a 3.5L w/ 9.75 CR pistons, BGT V8 induction, hugger headers, points dizzy. Any suggestions?
Jake

Marc
http://www.splitfire.com/plugtips.htm
Paul
Paul

Anyone ever heard of pressure relief spark plugs? It seems a bit far-fetched to me.
http://www.prepsparkplugs.com/frames.htm
Marc

Marc - sounds OK in theory, but from the description they are a 'one-shot' device in that if you *do* get enough over-pressure to cause pressure relief the plugs are scrap.
Paul Hunt

Yes I noticed the one shot aspect. It seems to me that they are modifying standard plugs in some way.
Marc

Perhaps the overpressure relief is to prevent hydrostatic lock, in which case replacing the plugs is a little less expensive than replacing the con rods and pistons.
George B.

This thread was discussed between 26/08/2003 and 28/08/2003

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