Update. Put 1000miles on it since the last 2 weeks or so. I got a little tick on the pass side again but it doesn’t sound like a cracked primary. My guess is the warped flange and the stock felpro gasket isn’t sealing. Driver side had a ting to it on high load that I could hear inside the truck with the radio off.
Today I said screw it and I was going to give it my last chance and started pulling the headers. I went to the parts store and found no rtv capable of 2000*F temps, copper is only good to 650 and the stuff I had on it was 700 intermittent and it turned to dust. Ordered this stuff on amazon for $1.66 or something insane from permatex and it’s exhaust sealer and it’s good for up to 2000*F! I got 2 3oz tubes for like $3.50 or something as an add on item and it arrived in 24hrs. I was going to use that to seal the collectors for a leak free seal.
I pulled the pass header, no cracks and no real visible signs of leaks but I knew it was around the back primary. To my shock I saw that hat might have caused or not helped it. The stock style gaskets have rivets that hold 3 layers of gaskets in alignment, MLS on the head side, then Heat shield, then graphite gasket material. The aftermarket headers have a flat flange and the rivit actually hits the flange and deforms the gasket which doesn’t seem to be helping sealing. The OEM manifolds are recessed between primaries so the rivit doesn’t affect anything. So I went to put the remflex gasket on and got the header bolted down finger tight.
Now I went to the driver side and started pulling the header. With a small dental mirror I scanned the primaries for crack and I saw one on the rear primary that looked like it was just forming. It almost looked like a crack in just the paint, I pulled the header out and saw the inside of the weld in the coating also chipped which tells me the crack is either just breaking through or is close. This is on the outer edge of the weld. So now I’m sitting there like WTF do I do. I haven’t gotten any Argon for welding yet at my new house and I haven’t setup any 220 wiring for the TIG yet. So I say screw it and threw the stuff in the back of the truck and will weld it tmrw at my rents place the next state over when I’m there for work. I threw the stock manifold on and stock gasket and bolted it all back together. I torqued down the pass side header but didn’t put the exhaust sealant on the collector bc I’m gona wait till I have the other header in and do a final seal up when I can pull the ypipe off and put the sealant on.
I finished up and started the truck and it’s very quiet. The driver side manifold u hear nothing and the pass side I can hear the engine and exhaust ticking away due to the thinner metal but no leaks (much quieter than before). I knew the remflex would work but they are a 1time use and not cheap so I wanted to make sure it was my last resort.
So I plan to do the header welding tmrw and maybe can get it all on this weekend. I personally have learned that stock gasket doesn’t work great and now that I know about the rivit thing I would not run them on any aftermarket header. Putting the remflex on would have been better first but I would have probably destroyed it taking it off so many times to fix the cracking and would have needed to buy more @ $35 each plus shipping. This is absolutely my last fix for these headers, if it decides to crack again I’m going back to stock. The $400 ish on the headers if I can get them returned would be put towards maybe a large sander I can plane the stock manifolds down to or who knows. Guys up here in CT want $$$ to deck manifolds.
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