MG MGB and MGB GT Tech Talk
Just changed mine out. Yes, its 430am. They were all gapped like SUPER big. the store said they get gapped to .024 I think, and the ones i pulled were gapped .056
Could be the cause of intermittent sputter-tastic action!
Yes, could be.
BP6ES NGK or N9Y Champion gapped to .025 for stock '72, .032 w/electronic ignition.
RS
Plugs designed to work with newer electronic ignition systems will have a gap of .050 or better. unfortunetly the electronic ignition systems in our cars, allison and pertronix will not put out enough voltage to make them effecient. Platumum plugs make things worse. stick with the N9Y or the BP6ES and use a quality set of wires.
Christian, gaps get larger as the plugs are used due to erosion of the tip and strap but also due to the energy of the spark (guess on this second part).
I've pulled plugs out of other (non-MG) cars of mine which were normally gapped around .035 to find they were at .050 or greater after 40k or more miles.
The Lucas coils put out 20,000 volts at their maximum. This is when everything is working perfectly. I have a GM based HEI distributor, made my Davis Unified Ignition, that puts out 50,000 volts and is triggered by a reluctor in the base of the distributor. The manufacturer recommends that the gap be set to .050. They make the coil themselves as well as the pickup module. I've never suffered a problem starting the car or while running it with BP7ES plugs, one range cooler to cope with the supercharger. RAY
I havd run RN9-Y and Nippondenso plugs in my 72B. I have an Accel super coil and am using std dist and points. Other than burning up a cap and rotor every other year, no problems. I have experimented with gaps from .026 all the way to .045 with no discernable difference in performance. This coil is rated at 50K volts. Had to go to this setup when I went to a 45DCOE Weber carb.
The HEI cap and rotor, from Davis Unified Ignitions, are made to a much higher standard and have lasted over 7 years of hard use. They even use Nylon screws on their rotors to prevent possible grounding of the spark to the advance assembly. RAY
I just bought a 1977 MGB 2 weeks ago. The previous owner installed the Crane Fireball XR3000 electronic ignition system and NGK BP6ES plugs with new spark plug wires. There is also a Weber carb installed. Yesterday I took the car for a decent ride (over 40 miles highway one-way) and found I had trouble restarting the car. Since everything seems to be in good order, I pulled the plugs and checked for fouling and gap. The gap was .080. This thread has been helpful, but I am still a little unsure of two main points:
1- Should I gap these plugs at .035 or .045, rather than the .025 gap recommended for non-electronic ignition, and
2- Should I go back to the N9YC plug.
Just to let you know, I ended up changing the plugs, using NGK BPR6EGP (Platinum) with a .045 gap and my little baby roared to life like a hungry lion.
