From my conversation that I had today..... The V bands are all mild steel. They were mild steel until an undetermined time which they are now chrome plated. Mine are chrome plated. These bands were not chrome plated. So all SS headers V bands are mild steel, the tubing is stainless. The V bands are now chrome plated, back then they were not. This was my understanding.
Over the past couple weeks I have spent some time with Mike from TA on the phone. .... We need to eliminate this as a leak possibility. TA has been very receptive and helpful in this manner and thought I would pass along this information. .
Make sure to thank Nick .. as i bet he had alot to do with TA helping you out
I have Poston SS Headers with the stock crossover pipe. The fitment has never thrilled me. I was ready to spring for some TA Headers but I'm glad I didn't now.
I've thought of putting a flex pipe just below the driver side flange. To me it seems the best place to put it since it would relieve the stress put on the headers from the crossover pipe elongating when heated. I think they flex a little side to side better than lengthwise but I may be wrong.
I think if I had the TA's I'd do the same thing and if they were too wide I'd cut some off the male slip joint and when things were aligned weld it up.
Every other car I've owned since 99 has had flexpipes in the exhaust, German and Japanese. Thoughts?
I don't come here often, but I've been watching this thread. Seeing the picture in post 121 brings this thought to me. The V-bands themselves aren't meant to do 100% of the sealing. It's near impossible to keep that surface 100% flat when welding it on. And because stainless grows so much it's hard to keep things like that lined up. Testing it at room temp will give completely different results vs. 900 degrees. The best way to seal stainless tubes (other than welding) is to have a tube inside a tube type joint. On a V-band, some come with a little locator ridge that is meant to keep the two flanges aligned, but because the fit is usually sloppy they can't do much sealing. I don't like that style I like the simple flat flanges. With the flat flanges you can let the tube pass completely through the first flange and part way into the second.
locator left, flat right.
Here is an exagerated view of how the flat flanges should be used. The arrow indicates the direction of exhaust flow. Notice the first tube passes through into the second flange. Ideally the fit between the OD of the tube should be tight to the ID of the flanges. Two things happen here.
The first tube is usually hotter than the second flange, so it expands and seals that way. This is also how slip joints from Burns and SPD are designed to work. They sell complete slip on collectors that work just fine in turbo applications.
The second, more minor thing, is exhaust gasses have to pass back upstream to make it out of the flange.
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I have been expressing and explaining your points that you present above. I have always questioned the position of my vband in relation with the "tube" metal stock that should insert into the female portion inside the header. I didnt have any real quality pictures till recently to share. You can see the lack of metal tube that was not entering the drivers header due to the angle of the tube. The new crossover should be even across and allowed to enter the header to help sealing. I think this is where the noise was apparent. By the time a gasket was used, there was literally no metal tube going into the drivers header. View attachment 296855