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MG MGB GT V8 Factory Originals Technical - Oxygen sernsor thread

Hi All,
1994 Rover 4.2L with 14CUX EFI.
What is the correct thread for the O2 sensor bung(s) that I will need to weld to the exhaust?
Is it M12 x 1.25 ?
Where can I buy the correct size bung, other than just welding on a nut from the hardware store?
Thanks
Tony
Tony Bates

Tony, most of the O2 sensors I've run across are the same thread as the larger size sparkplugs, 14mm I thought, however Speedway Motors sells bungs in 18mm thread size. http://www.speedwaymotors.com/GmSearchResults.aspx?q=oxygen&SearchTitleDescr=True

Bill Young


Yes, M12 x 1.25 (which is an oddball size that pretty much only Rover and Nissan used.)

I don't know where to buy an M12 x 1.25 bung.

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One might think that you could switch to a regular bung and substitute a regular oxygen sensor... but the problem is that Rover used "titania" oxygen sensors instead of "zirconia" oxygen sensors, so using different threads was apparently deliberate to keep people from substituting a sensor with a different output/signal.

However, I'm not sure that titania sensors haven't sometimes been made with the regular (M18 x 1.5?) thread-size. I think I saw them once... cross-referenced to an early Toyota EFI system. (Al Wulf was asking me about this too...)

If that mystery Toyota/large-thread/titania sensor actually exists, presumably the same bung would alternatively support either Rover EFI or wide-band O2 (Megasquirt EFI or aftermarket air/fuel gauges) through a simple sensor swap.

I welded regular sensor bungs onto my exhaust earlier this summer because I'm keen to try using a wideband sensor for general tuning (someday when I can afford the electronic gauge.) I wondered whether it would be feasible to machine an adapter/insert, because one of these days I'm gonna have time/money to install Rover EFI too.

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reference info on Rover/Nissan O2 sensors: http://www.britishv8.org/Articles/Rover-14CUX-EFI.htm
Curtis

Hi Guys,
Thanks for the input, I'm always amazed at the depth of content on BritishV8.org.
It looks like I'm welding M12 nuts on the headers.
Thanks
Tony
Tony Bates

Hi tony,

I also use the RR ECM. I had to make my bungs on a lathe. Can't buy them. The bolt idea also sounds like a good option.
M Mallaby

Done,
Two M12 x 1.25 jamb nuts (thin ones) are now welded onto the down pipe, work great.
Thanks
Tony
Tony Bates

This thread was discussed between 22/08/2007 and 28/08/2007

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