O2 Bung placement positions

Would you add two bungs for o2 sensors in each manifold or would you only add one sensor. Seems like two would test both banks of carburation. Another option, would you install the bungs further back in the exhaust system? Analyzing the a/f with a machine will give fairly exacting results.

Does the size of the bung matter? I just bought one for my GTO for an upcoming dyno day and they did not seem to indicate the need for one on each side of the engine for all 8 cylinders.


I would use two fairly close to the join where the manifolds meet, if you are running standard twin carbs thats going to give you a relatively accurate reading for each carb.

unless I can get a convincing reason otherwise, I will soon further modify my 420G system by removing the tiny front mixer that joins the downpipes pipes, (back to large twin SS mufflers, and straight thru SS rear pipes), and replace them with twin 9" muffled hotdog style

This will completely separate each manifold thru to tailpipe.

intention is to get 2 bungs, one in each front downpipe, and at least 1 wideband O2 sensor

The tiny mixer must be there for a reason, such as back pressure, but I am hoping that the ability to measrue both mani outputs on a tri carb vehicle will outweigh any negative effects of not mixing…all opinions welcome

Not sure about removing the cross over, I would be inclined to leave it in place, does it help with scavenging?

I dont know, probably, its only about 8" long and 6" wide, and to me seems restrictive.

It needs replacement in any case, due to age, so I have to decide

I have sen a 420G set up identical to how I thought to do mine

Some Jags had dual mufflers as an option as I understand, such as XK120/150

Well, Jaguar spent quite a few $$$$s worth of engineering, to optimize exhaust layout for the cars street performance envelope: if you have better data, supporting the change, go for it!

The size of the bung is not important.

Placement should probably be no less than three feet from the exhaust port, otherwise the sensor may be overheated. There ought to be some guidance on that on the Innovate LC-1 website.

kind regards

I installed two bungs in my pipes, they are just above the bends where the downpipes turn towards the rear and go under the cabin. I can reach the sensors from the engine bay. I originally had 2 bungs and one sensor, with a plug in the other, but after a few months of switching it back and forth I just installed a second sensor and gauge, so I have real time view of both pipes. It’s made a huge difference in how well the car runs being able to fine tune each carb. The Mk2 has no mixer it’s just two independent pipes so no comment on that.

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What brand of a/f meters are you using?