I have a new Offy intake. It has a threaded hole (3/8) right below the carb and opposite the center bolt (above the heat riser). Is this for an oxygen sensor ? I just put a bolt in it to plug it up.

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"Nothing in all creation is hidden from God's sight. Everything is uncovered and laid bare before the eyes of Him to whom we must give account."

Oxygen sensors go in the exhaust stream, not the intake. Air temp sensors commonly go in the intake. You can install a hose barb in the hole if you need it for vacuum, otherwise just cap it and all is well.

O2 sensors read levels of unburned O2 which by nessesity would place them in an area after combustion, I belive a header collector would be a better choice for a O2 sensor. The threads on the intake are a National Pipe Thread (NPT) hex key plugs are availible at your hardware store. The 4b Offys a manifold should be fun Bruce Johnson

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78b4ramSnortbed/6

I think it may be for a water jacket ??? Anyway, I'm not using it. I fired it up today, open headers
I can't wait to get the mufflers on and the linkage finished !
BTW, Offy includes a set up for the carb linkage if you have a rod set up.

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"Nothing in all creation is hidden from God's sight. Everything is uncovered and laid bare before the eyes of Him to whom we must give account."