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MG MGA - Spark Plug Heat Ranges/HRG Head

Greetings all,

I am trying to figure out which Champion spark plug to use with the Derrington HRG Crossflow head on my 1600 Coupe. I have been advised that the HRG head had/has a tendency to overheat and warp. Something about the poor design of the cooling ports. If that is true, then that is truly depressing to hear. If true, I was wondering if using a "hotter" or "cooler" plug might help off-set that characteristic of the head. I think it calls for a champion N5 but I'll have to double check that. Would going to an N3 or N7 provide some advantange? Thanks!
robert maupin

First of all the champion plugs are in mine and many others opinion the worst plugs in the world. That said it is of course personal choice and I like NGKs. The heat rating of a plug is how hot the tip of the plug becomes. This is important for keeping the plug clean and keeping the tip of the plug cool enough to prevent pre ignition. With that in mind the NGK 6 range is perfect for most applications. If you got pre ignition then a cooler plug could be of benefit. With NGK that would mean changing to a 7 or even an 8. Champion work opposite and would require a reduction in number to a 3 say.
If on the other hand the plugs oil up regularly a hotter plug could be of benefit say an NGK 5 or a champion 7.
The only way the plug could affect the head becoming too hot would be if detonation (pre ignition) occured thus then a cooler plug could be used although other things ought to be addressed prior to that.
Bob (robert) yes I own an MG Dwarf!

Bob and I rarely agree on anything but in this case he is absolutely correct. Champion plugs are in my opinion not worth using. NGK are the way to go. BP6ES with a point ignition and .028 plug gap. BP6ES-11 for electronic ignition and a .044 plug gap. Would be the starting point, then read plugs as Bob reccomends.
R J Brown

RJ

Why the BP6ES with a point ignition and the BP6ES-11 for electronic ignition? I would think that if you are running a radio (some of us do) that the P^6ES resistor plug would be the more desirable.

Thanks

Larry
58A (with radio)
Larry Hallanger

Robert- email Bill Spohn and ask him-
http://www.rhodo.citymax.com/HRG.html
Or he might even see this,he has experence running these heads and will know.Literature of the day says engine runs 20 degrees cooler. Then when your done,how about some pictures and your story, head # carb size & type?
gary starr

BP6ES and BP6ES-11 are the same except for plug gap(-11 means a 1.1mm gap), NGKs comes pre-gapped. With electronic ignition and an appropriate coil a wider gap will give a hotter spark, with points and a normal coil a wider gap can cause a misfire. BPR6ES and BPR6ES-11 are the resistor versions of the same plugs. For a radio you should use resistor wires, resistor plugs or both and a noise suppression condenser on the generator or alternator.
For a complete explanation of what all the letters in the NGK system mean read a catalog, it is quite informative. Remember a 5 is hotter and a 7 is cooler than a 6.
R J Brown

Robert,

I've used both NGK BPR6 and 7 ES in my (high CR and high output) engine runs fine in all weather conditions, even during summer. Don't worry and enjoy it ;-)

Alex
Alexander M

This thread was discussed between 13/11/2006 and 20/11/2006

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