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Bored&Stroked · 05-22-2025, 07:18 PM

Actually, you do not want the O2 bungs close to the block - ideally they should be about 3 feet back from the block and installed so the sensor will be at a 10:00 or 2:00 o'clock angle when installed.

But, since the flathead has internal exhaust passages (about 8" in length), then you can move the O2 bungs a bit closer (like 6" from the end of the tubular headers). What you need to make sure is that there are NO exhaust leaks in the system - as they can pull oxygen in and ruin the readings.

The other sensors that are installed right next to the block are EGT (exhaust gas temperature) sensors. I weld those little bungs (1/8" BPT) as close to the block as I can (the angle does not matter). I like to have one on the rear cylinder and one on the center (mixed) cylinder. These really only work with tubular headers - probably not really viable with stock manifolds.

When I setup a flathead exhaust system I put both EGT and O2 bungs in - so I have both to tune with. The O2 sensors are the most valuable, but it isn't a bad thing to see how the EGTs are reading - especially on a high-output blown engine.

05-22-2025, 07:18 PM	#20
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,910	Re: Edelbrock Slingshot air flow imbalance Actually, you do not want the O2 bungs close to the block - ideally they should be about 3 feet back from the block and installed so the sensor will be at a 10:00 or 2:00 o'clock angle when installed. But, since the flathead has internal exhaust passages (about 8" in length), then you can move the O2 bungs a bit closer (like 6" from the end of the tubular headers). What you need to make sure is that there are NO exhaust leaks in the system - as they can pull oxygen in and ruin the readings. The other sensors that are installed right next to the block are EGT (exhaust gas temperature) sensors. I weld those little bungs (1/8" BPT) as close to the block as I can (the angle does not matter). I like to have one on the rear cylinder and one on the center (mixed) cylinder. These really only work with tubular headers - probably not really viable with stock manifolds. When I setup a flathead exhaust system I put both EGT and O2 bungs in - so I have both to tune with. The O2 sensors are the most valuable, but it isn't a bad thing to see how the EGTs are reading - especially on a high-output blown engine.