Does anyone know who sells them? I only see up to 3".

 

I needed a bigger one as well so I bought the rectangular piece with the threads in it that "attaches" to the exhaust pipe. Then I just found a couple good band clamps and attached it securely. I will weld it in place when I have the time and the weather. This has been on the car for two years and still no leakage. It was cheap and easy to do.

 

I'm guessing you put it on a side pipe? What would be the optimum location?

 

On my C3 I installed the bung on on my "Chambered Exhaust" pipes near where it connects to the Long tube headers. They say to have it at an angle to keep the tip dry and withing a certain number of inches of the collector. I have mine about a few inches back from the connection to the exhaust system to the headers and it works well. The hardest part is drilling a hole from above the center of the pipe while it is under the car. I am going to install another "BUNG" that is what they called it on my left side exhaust pipe at a moment this spring. I want to see that my system is working well for both sides of the engine.

I literally jacked up the passengers side and put jack stands under it. Then I started looking for a place where I could squeeze in my Right angle drill and get a hole above the center line.

This is a picture of the part I used from Holley. I just used bigger clamps and it still sealed with the gasket. This is picture of Holley's 3" set which I believe is the largest they make.
Good Luck!

 

Why not just get a bung welded on at a muffler shop?

 

Can the average muffler shop weld stainless? I guess with modern cars stainless exhaust is more common...no rush anyway, I probably won't install the fuel injection before a year or more.

 

Which fuel injection system are you going to use on your Corvette? I purchased a new Holley Stealth Sniper EFI system and love the way it works. I have mine sitting on top of an Edlebrock RPM Air Gap dual plane intake and I am lucky as that intake has no issues like other dual plane intakes can.

I bought mine because of the Holley system's abilities and software. It is a well designed system and has worked well so far. The software is amazing and will allow me to make everything work from one controller. I also like the ability to control my timing even with my MSD Billet Tach drive Distributor.

They probably make the plain round weld-on type Bungs in stainless steel and that would be better to weld onto your Stainless pipes. I would stay away from dis-similar metals being welded together. I might consider the Holley Bung I showed you earlier and find the clamps made for it. The issue would be finding band clamps that will last. For that I would go to a "Marine supply" store and see if they carry bands clamps that large. I got several 4"+ band clamps that were stainless and lasted for years. They would also be available for trucks as they use large clamps as well. You will need to be a bit resourceful here but they are out there.

 

I got the Sniper, used from a forum member. I don't have it yet.

 

If you do weld, you can put the hole in the 4-5 o-clock area and get a longer or angle cut bung and fit it over the hole so the sensor will stick straight out or slightly upwards to the inside. That'll get you more frame clearance and it'll work just fine. The warnings on placement in the pipe are not because it has to be there in the pipe but rather to not have the wire end lower than the sensor tip end.

 

Regarding the installation of the O2 bung. I was told by several sources to drill the whole at 2-2:30. You need the tip to stay dry and drip clean if needed. The higher angles ensure the EGR will last longer. The longer Bung like mines had a 3/4" ring on it to slide into the hole to line it up. Holley has on their Instructions for their EFI systems to mount the Oxygen sensor above 10* over the center-line of the tube. They want the angles to keep condensation from collecting inside the O2 and damaging it. The 10* looks more like 2:00 so be sure you have room. Here is a copy of the complete installation instructions for the Sniper Stealth EFI system I bought. It has instruction for O2 installation on page 8 that show a higher than center-line angle to keep the tip "dry" and free of condensation.

https://www.efisystempro.com/image/c...structions.pdf

I have been careful and followed their instructions so I don't have to change the O2 very often as it gets expensive. I followed their instruction carefully and have a successful installation so far. I am getting parts together to install the Timing control portion of my installation over to my Holley EFI controller. It is a well designed system and the parts seem to be made well. Once pressurized my fuel lines hold the 50+ psi for days and weeks. I have no issue with waiting for the engine to inject a start-up dose of fuel and then cranking. I am going to use the Holley EFI software to control my Water/Methanol injection system as well as the engine timing. The entire Holley EFI systems are amazing with what they can do for us. The best part is my system looks like a big Holley Dominator sitting on top of my engine, very few people can tell it is fuel injected.

Definitely use an "In-Tank" style fuel pump. You don't hear a fuel pump on my system and with a DeRale PWM electric fan control system my fans start up at 50% power and slowly speed up only if the heat increases. This makes a C3 with fuel injection much nicer to have to deal with. Getting it tweaked is somewhat challenging at times but with good support it is a breeze.

 

The sensor doesn't have to be at 90* to the pipe, especially when dealing with a 4" diameter pipe. You can easily put it in at 4 o-clock and still get the angle recommended.

 

It is all done to keep condensation from filling the O2 sensor shell. They don't last if water collects in the O2.

 

i think what he is saying is it can be offset upwards so it goes in at 4 o:clock and still points downwards. i have some angled bungs. made to tilt forward or back but can also point down. not a clamp-on though.

 

The new theory is the longer ones are better. Moisture as well as soot. Also if running leaded fuel they do not last as long if you mix any race gas in. My last set that came with a Innovative wide band were the long ones.

Nice down pipes-what do they fit?

 

Band clamp wise I would check with the diesel truck folks. They run some pretty large aftermarket exhausts.