My already loud car gets really loud after about 3,000 miles (which unfortunately is every 12-18 months for me ).

The 914-6 gaskets always get "blown out" very easily. My car is so loud right now I was sure I had to weld up some muffler cracks or something, but nope, just blown out gaskets again.

Anyone else have this problem? Any solutions? I'm considering replacing both flanges with something sturdier...





-Steve

Typical. The warped and/or uneven rough flanges cause the problem all of the time. By the way what kind of a 916 rear transmission tail cover is that?

Yup, flanges are warped.....a muff shop can fix that or you can weld on new ones or if you are inclined a lot of file work. .

You can try applying a muffler paste to help seal them, i have in the past with good results.

If you do go the replacement route, go with a flange with larger surface area, and three bolts. You said, sturdier, but I considered you might have been thinking 'thicker'.

I have almost the identical setup and so far no problems. Of course now that I said that they'll blow at WCR.

As others have said most likely warped flanges. Sometimes the damage is generated by excessively tightening the bolts. Once they leak, there is a tendency to tighten even more and warping them further.

Suggestion.....Take the exhaust off the car and use a table mounted belt sander to resurface the flanges. It saves the welding. Even if you have new flanges welded on, they will warp from the welding and you will still have to resurface with the belt sander. Most shops would resurface after welding anyway so just skip the welding part....

Also I like to use the largest, thickest washers that will fit under the bolts to spread the load.

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I see you have aftermarket heat exchangers and an aftermarket muffler. This probably adds to your problem too.

What muffler gaskets are you using ? I have a 3.0 in mine with headers and a M&K muffler and I'm using the gaskets that have copper foil on both sides. Bought them from Pelican parts. Have them on my 911 also and no leaks on either car.

> By the way what kind of a 916 rear transmission tail cover is that?

Vellios


> aftermarket heat exchangers and an aftermarket muffler

Yes, B&B (I think) headers with heat, and M&K sport muffler.


> Take the exhaust off the car and use a table mounted belt sander to resurface the flanges

Thanks for the tip. I took it apart yesterday, and used a belt sander to flatten the flanges. Just by looking at the ends they did look dead flat, but when I sanded/polished the flanges, the tips did polish first. There was so little taken off I'm not sure if that was the problem, but it did make for a nice shiny surface to bolt everything back together.


> What muffler gaskets are you using ? I have a 3.0 in mine with headers and a M&K muffler and I'm using the gaskets that have copper foil on both sides. Bought them from Pelican parts.

Yup, I'm using the same ones. Just standard <73 911 muffler gaskets.

We'll see what happens. It's back to just being loud again, and hopefully it lasts, but I'm not so sure.

I wonder if the old (< 73 gaskets) aren't just up for the heat and back pressure generated by a 3.6... ?

This type of design seems to make a lot more sense:

http://www.jegs.com/p/Dynatech/Dynatech-V-...753318/10002/-1


Or like was mentioned, even if there were 3 bolts per flange like the later 911 mufflers:

https://www.sierramadrecollection.com/store.../2925_small.jpg

-Steve

Steve, in your picture it almost looks like the muffler is hitting the tranny. It also looks like you had to add some extra denting to the muffler. If the muffler is hitting the tranny perhaps the muffler can't seat to the headers properly.

3.6 should not matter if there is a seal.

If there is ANY leakage now the gasket will eventually blow out again. Must be perfectly sealed to last.

Lastly it's very important to assemble EVERYTHING loosely first. Bolt on headers loosely, then the muffler and gently snug the bolts, back to the headers and finally the final torque on the muffler bolts. If you tighten the headers firmly and force the muffler into place that could be your problem. Good luck

> Steve, in your picture it almost looks like the muffler is hitting the tranny. It also looks like you had to add some extra denting to the muffler. If the muffler is hitting the tranny perhaps the muffler can't seat to the headers properly.

Yes, the Vellios mount sticks out pretty far, and there was actually a lot of "massaging" (read: hammer) of the muffler to get it to fit. Same when I used a OE-style Dansk. It needs to be dented in as much as 1.5" to get it to fit...

-Steve

Had the same issue with the WEVO but lengthened the collector a little to solve the problem. The M&K is so small it has plenty of room to move rearward. I first bolted the extensions to the muffler and then welded them to the collector and perhaps the reason my joint fits so good.
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