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MG MG Y Type - Hotter spark plugs

The NGK equivalent to the standard Champion L.10.S (or L.82.C) is B6HS. Fouling of “Standard Heat Range Plugs” is a common problem with unleaded fuels – especially driving “around town” & cold starts.

I adjusted the float correctly and changed the needle for a leaner type. Even then, the mixture was too rich, even with jet all the way to the top. After a few hundred miles, the plugs were fouled at the gap with much black carbon deposits. The engine started hesitating.

In identical spark plug types, the difference from one full heat range to the next is the ability to remove 70°C to 100°C from the combustion chamber. For NGK, the lower the number, the hotter the plug.

So I swapped my B6HS for B5HS and the problem is clearly much more under control. The tip is now much cleaner and brownish, as it should be. Engine temperature (which was unusually cool) is more normal and performance is a bit snappier too.
Gilles Bachand

I just wondered if you get a little puff of smoke after a down hill run on closed or low throttle. Also have you checked the compression on all cylinders. I think it should be I think about 150lbs with the carb fully open. My engine has a CR of 8.5 and is 170lbs. I once had a situation like this on just 2 cylinders and later found broken rings, although it could just have been worn rings, also worn valve guides may be the problem. Its just a thought.

Best of luck Bryan
B Mellem

My compression is a steady 140 on all cylinders and I never get a puff of smoke when operating. Only a small one at startup if it has been sitting for a week.
Gilles Bachand

Could be its petroleum refined from Alberta shale oil, you should try Brent crude its a much superior blend. Bring a can over next time you visit. Bryan
B Mellem

Joking aside Gilles, I did have a little problem on the YA where the choke didn't always return the jet correctly and found the little return coil spring had lost its tension. This indeed gave a varaible rich mixture. Bryan
B Mellem

The NGK website in Australia gives a very good explanation on why hotter plugs are required for unleaded fuels. I have fitted "B5HS" for several years, rather than the L10 equivalent of "B6HS".

My YT also runs "lean" needles that are mounted 0.025" out from the dashpot to lean off the mixture even more.

And it does not run hot in traffic, climbing mountains, towing a trailer or on the highway. I have an electric temperature gauge mounted just below the thermostat, so know how "happy" the engine is all the time.

The change to hotter plugs is well worth the money spent.
A L SLATTERY

I have 2 sets of NGK plugs. If I were to be doing a lot of city driving, I would use the B6HS. As I live in a rural area and 95% of my driving is on the h'way type of roads, I use the B9HS plug. I think the decision to use any products of this nature, such as oil, gas, plugs, etc. should depend on factors like how the car is used, and the nature of the climate conditions.

George
George Raham [TD4224]

Bryan,

Sorry to burst your bubble, but the oil from Alberta is not from shale. Its from sand - a big and expensive difference.

Its the Yanks that are planning to extract oil from shale.

Gord Clark
Rockburn, Qué.
Gordon A Clark

This thread was discussed between 14/06/2012 and 12/08/2012

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