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What's the best place for an O2 sensor on a set of aftermarket headers?



Sorry to be such a questioner.

I have a set of smog-friendly full length Hedman's for my car that I want to install. I purchased a heated O2 sensor so position isn't a worry. I know I'll have to run an extra wire to it too. I also have the bung that I need to have welded into the header. My question is where should I have the bung placed? I'm thinking somewhere right before the collector. If it was put into the collector wouldn't it contact the pipe coming in from the cat?

Also. What suggestions do you have for somebody who's going to install headers? I think I need to buy some better plug wires and some sort of clips or something for the wires to keep them away from the headers. Any pics of your setups would be great if you have them.


Good question, and I am glad you asked. Just did this a few weeks ago, and will be doing it again soon on the big block. You want the O2 to be about 4-5" after the point in the header where all the pipes come together. So, it actually often works best to have it installed in the collector that gets welded to the rest of the exhaust. Too close to the part where the pipes come together and you don't get a good blend. Too far, and you get into that CAT.

Congrats on the heated O2 decision. That is the only way to go. It is EASY to wire. Simply find a good source of 12+ key on to one side, ground to the other, and connect the feed wire right back to the computer harness.

As far as installation, I assume this is on your 1980 model? If so, you need to jack it up high and work them in from underneath. It may or may not require removal of the starter. At the least, pull the 12+ wire loose at the battery. It is way too easy to make contact with the starter 12+ and cause some nasty sparks while you are struggling to fit them in.

You will have to play with different types of plug wires (90, 45, and straight boot) tips to see which fit best with your headers. Accel makes special shorty spark plugs that make life easier to keep the wires clear of the pipes. You can usually use the retainer bolts for the valve covers to attach to some kind of plug wire loom and hold them out off the header pipes.

In the end, you will just have to route the wires in such a way that it works best for you both visually, and saftey wise for the wires.

One last thing. Take plenty of time, and get creative as possible to make sure that you replace any bracing that was stock from the accessories back to the stock manifold bolts. Why? Well, often fellows just omit these brackets as they don't typically fit right back on. In the end, you will throw belts, crack accessory brackets, and just have a world of headaches. I often reuse the stock manifold long bolts with a sleeve and retrofit the alternator or a/c brackets with some grinder action, and a quick trip to the welder if needed. This will make your project more professional and provide many more years of trouble free running.

Good luck.

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