Bung on top of crossover pipe Y

I’m replacing my left exhaust manifold gasket. Anybody know what this “bung with a bolt in it” is for?
See photo.
Also what is the bedt tool to loosen the upper left (driver side) of the 4 nuts attaching the crossover pipe to the exhaust manifold? It squarely blocked by the oxygen sensor! I’m thinking of using a 17mm crow foot because a 17mm socket won’t fit over the nut without removing the oxygen sensor - which I can’t remove.

What is the best tool to remove the oxygen sensor (if I have to remove it)? It points toward the side of the vehicle and a longer sensor socket won’t fit over the sensor. Is it 13/16” or 20mm or 21mm?

Quote:

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Originally Posted by Ed81DMC

I’m replacing my left exhaust manifold gasket. Anybody know what this “bung with a bolt in it” is for?
See photo.
Also what is the bedt tool to loosen the upper left (driver side) of the 4 nuts attaching the crossover pipe to the exhaust manifold? It squarely blocked by the oxygen sensor! I’m thinking of using a 17mm crow foot because a 17mm socket won’t fit over the nut without removing the oxygen sensor - which I can’t remove.

What is the best tool to remove the oxygen sensor (if I have to remove it)? It points toward the side of the vehicle and a longer sensor socket won’t fit over the sensor. Is it 13/16” or 20mm or 21mm?

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Photo of the bung on top of the crossover Y pipe Attached

its removable so that you can insert a pipe and using a gas analyzer tool you can read the AFR or CO (mixture).

there is one on each side so that you can read each bank.

I found the top bolt on the driver's side was easiest to get at with a combination wrench from above. Even then it wasn't easy.

Cheers
Steven

Oxygen Sensor is 13/16". Best tool to remove it is an oxygen sensor socket and/or an open end wrench, right after heating the bung with an acetylene torch.

If you don't have an acetylene torch or even a turbo torch, run the engine to get things hot and then try to remove the sensor. Obvious warnings - wear gloves, don't touch the hot pipes, etc.

Hot is good but you really have to get it red hot to have the full effect. The only way to get it red hot is with an Oxy-Acet torch.