12a Headers
 

Does anyone make custom 12a headers? I am looking for something to fix my current exhaust problem. Yes I know racing beat sells "great" headers. I am looking for true duel long tube headers.

Thanks

There are others out there like pacesetters but they are so thin and cheap they burn up from the heat of the exhaust. The RB SP header are dual pipe at the collector and the remaining center section is dual as well. The only place it joins is right before heading over the axle into the muffler. You could make that dual as well but there is a scavenging advantage when the tubes come together and RB has done the engineering to pretty much make it at the ideal spot. They also sell all the header tube and bends so you can make your own if you want. They key to what they make is the thickness of the tubing wall and the diameters. Its all part of the solution.

But they don't make one that comes with an o2 bung already put in it for a 12a. When I asked if they would put one in, they where surprised by the question.

Were they willing to install an o2 bung for you? If not a good machine shop can do no problem.

get the header then have a muffler shop weld in an O2 bung.

Buy an o2 bung, drill a hole, take to a place to get it welded in.

An o2 bung on the header might be too hot for the sensor, might be better to put it midway or further back.

O2 sensor
 

What they said,did this to my SE when i installed streetport exhaust,as i wanted to keep O2 sensor for fuel economy. No problems,no issues. Closer O2 is to engine,within reason,warms O2 sensor to come on line sooner(needs to be 600 degrees) and makes readings more accurate.
When installing,avoid positioning lower than horizontal to keep water/condensate from collecting in sensor.
https://cimg6.ibsrv.net/gimg/www.rx7...21033ed006.jpg

I pickup up a GlowShift AFM brand new at a local auction for really cheak ($20).

GSLSEforme - I see you have the sensor in the rear rotor header tube. Is there any advantage to one rotor or another or further back in the system so you get both rotors. Or maybe one sensor/gauge for each rotor?

Rear rotor runs slightly hotter than front,why Mazda put O2 in rear rotor position in oe exhaust manifold. OE sensor is unheated and relies on exhaust temperature to heat it to operational threshold. In the header where it is,is close enough to warm it to temp without it getting too hot.

Further back in system after exhaust is collected would be ideal,but further back in system you go the cooler exhaust gases get and O2 operation gets more inconsistent. When these cars were designed and built,heated O2 sensors were in their infancy and not commonplace.

Today they are on every car and all the way back in system to just in front of cat converter and their heaters start as soon as engine is running so they get up to temp faster to control emissions.

On a RB header built for single exhaust,the 02 sensor is placed back by where header is collected so its exposed to influence of exhaust from both rotor housings equally. On my car i'm running a full streetport system and its not collected til inside muffler at back of car.
I use the front header tube for exhaust backpressure to supply 5th& 6th port actuators. Se FI system doesn't use O2 input til ECU sees signal from 5th gear switch.With factory ECU,there would be no advantage to more than one O2 sensor as system couldn't take second O2 input.
I wanted to keep O2 sensor to allow ECU to fine tune fuel mixture to keep some fuel economy on longer drives.
On a 12A or 13B carbed car,or standalone engine management for FI you could run sensors in each tube for tuning purposes,or after collector further back in system with a heated O2 sensor.

I have built my headers and exhaust using sprinkler pipe for the past 13 years. It is about double the thickness of regular exhaust tubing but can still be bent without kinking.