Are the heat shields on the stock F355 headers welded on or bolted on?
Not just welded, but welded and crimped all around, in between and encircling each exhaust gas sampling port.
jm3's got it, crimped all the way around and spot welded every few inches along the seam, not alot of fun to remove.
Yes, crimped and spot welded all the way around, not fun to remove. Also packed with insulation (probably asbestos...Italy doesn't care if it causes cancer) that is always broken down and powdery. A nasty mess to deal with. Someone with ALOT of time could probably remove them fairly nice, but I bet they'd look like hammered hell trying to reuse them.
That's what it looks like from the top side. I guess that's not all bad. Is it possible for debris to get trapped in/on them at all? (Chasing rattle coming from that zone.)
Thanks to all for the education. Now the tough question - without removing the header, is there a decent way to inspect for such a thing?
Without removing the header it would be really tough to tell if any debris got inside the header. The heat shields can be removed , intact, however, as it is done by a few companies that specialize in rebuilding the headers and they always re-install the original heat shields. The white insulation material is fiberglass packing. It has great heat resistance and is used in motorcycle muffler packing. If you think that you hear a rattle from the header area then perhaps your header has failed......as the headers can be removed while the motor is still installed in the car it might be worth an afternoon to remove the suspect header and closely examine if, removing the heat shield if necessary.
Thanks. I'm chasing a funky issue since its shaping up not to be the bypass valve or a cat. I'll probably be in for some fun diagnosing.
+1. It is possible for the header tube to fail, and the edges of the failure point could be touching or rattling against the shields. Have not personally seen it, but could picture that happening. Can you see the insulation material working its way out from under the shields? (basically being blow out?) If so, then you have classic header failure and that is the source of the noise.
