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Crossover corrosion.

429 Views 13 Replies 7 Participants Last post by  56pan
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I'll try to post pictures of what I found today on my exh. crossover. My boost press. had gone from 13 psi to 8 psi at WOT and was slowly decreasing. I noticed I was rolling the coal also at WOT. Checked fuel pressure with a gauge taped to the windshield at WOT and it dropped to about 1 psi. From what I understand this is sufficient at WOT. Checked all the ducting from the compressor outlet through the intercooler to the intake and was sure there were no leaks. Finally noticed when I got under the truck with it idling I could feel an exh. leak below the driver's side manifold. Took the crossover off and the pictures tell the story. I had wrapped the crossover with header thermal wrap about 8 yrs. ago when I put the mandrel bent one piece on the truck. I remembered there was a discussion concerning wrapping the crossover on either this forum or one of the others several years ago, but I couldn't find that again. The gist of it was that there was a disagreement about the thermal wrap on the crossover. Most said it was a good idea, but the detractors said it would cause the pipe to corrode. Which the attached pictures reflect and the detractors had a good point. I put on a new 2 piece Diamond Eye crossover today after giving it 3 coats of VHT and then wrapping it with new thermal header insulation. I'm a retired airline mechanic and on the Boeing, Douglas and Airbus ships, the GE, Rolls Royce and Pratt and Whitney large turbofan engines all have thermal blankets on the turbine sections. To maintain efficiency is what I understood, not for cowling protection I've also seen large Caterpillar diesel generator sets with blankets on the exhaust feeding the turbine of the turbocharger. If it's good enough for those engineers, it's good enough for me. Just my opinion and worth what you're paying for it. At my age, if the crossover corrodes through again, I'll be long gone.

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That's some quality Swiss Cheese you found
I thought VHT was only heat resistant to 900*?
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Good information. Thanks for posting your findings.
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I didn't paint the one in the picture when I put it in, Dually. Painted the replacement with the header paint in hopes that it would slow down the cancer.
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You could try the ceramic coating Twisted Steel Performance offers. It might live longer under there.
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ttI'll stay with the header paint, I guess. I'm in NC and very little salt ever gets put on the road in my area.
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And yet your crossover looks like termites attacked it. You wrapped the last one and it rusted through, so you are doing it again? I would have it ceramic coated or forget about wrapping it.
Yes. Exhaust wrap will cause exhaust pipe to rust out. I have seen wrapped headers that looked like your crossover.
IMO unless using your truck in competition or squeezing every bit of power out of the engine. Exhaust wrap is not needed. You may be better served by a Turbo blanket. Which reduces under hood temps and increases turbo efficiency. Without rotting the exhaust pipe.
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This is a common discussion with my V8 performance crowd. general consensus is to have them ceramic coated from new. It will not only preserve the x-over indefinitely but reduce surround temps. I ceramic coated my headers in the late 90s. I'm still running the same headers today.

"Wrap does work better at keeping the heat in the manifold. This is undeniable."

From the article in the link and I agree with the author. In 47 yrs., I never once saw the turbine section of any gas turbine aircraft engine with ceramic coating on the hot section. If it was as good as thermal blankets the ceramic coating would have been used. I imagine the 3 coats of VHT paint I put on the new crossover will delay the rust through more than 8 yrs., which is about how long the first wrapped crossover lasted. As said in my post, at my age I don't give much of a s&*t how long it lasts this time as I'll be planted before it rusts through again. Just a thing with me and efficiency and why the turbine housing has a blanket, both exh. manifolds have blankets, the crossover is wrapped with thermal insulation and I put an intercooler on the truck. Don't want to turn this into a pi$$ing contest, but thermal wrap does a better job of insulating the heat than ceramic coating. And, yeah, it won't last as long.
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Not wanting to beat a dead horse, but turbine aircraft exhausts are stainless steel, and when wrapped, tend to dry out quickly during use, including taxiing, so are dry when parked. A car or truck on the other hand, get driven in the rain and parked with the wrap wet.
Stainless used on aircraft engines doesn't have much of a corrosion problem. Anyhow, I'll deal with the crossover corrosion whenever I have to again. I figure it's an expendable item.
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You answered yourself.... use a 304 or 316 stainless steel crossover
no more problems
And where would I get that, Alex?
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