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New SS Exhaust on sale on ebay

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From a March 2009 Randy Forbes post
"I do not recommend wrapping your exhaust (assuming tubular headers) with an insulating wrap. A thermal barrier coating, applied inside and outside is a much better solution, and the headers will last A LOT longer.

The wrap may show immediate benefits, but it will soak up water (leading to rust) and will also fatigue the metal by subjecting it to intense heat that it cannot dissipate. Your wrapped pipes will live a much shorter life."

I guess I won't be wrapping my manifold or pipes.
 
RestoreThemAll said:
The ebay price for SS was no more than the regular mild steel. So I can't lose. If I don't like shiny I can always paint it black.
If I had to go full price you've convinced me that mild steel would be just fine.

Bob, did you wrap your exhaust manifold? Or any part of the exhaust system? Mine is not installed yet so its a good time to consider it.
The vendor that you recommended silicone paint has wrap to.
"This stuff works really well: https://www.designengineering.com/ca...licone-coating"
Click to expand...

I wrapped the down pipes, but not the manifold (I think ceramic coating may be better for this, but the wrap might work as good if not better). No downsides as far as I can see and, although I haven't measured it I have to believe it keeps underbonnet temps down (the exhaust is pistol hot--I don't remember it being that hot before the wrapping). DEI also has stainless 'tie wraps' for securing the wrap, and I painted the wrap with the silicone spray.

Just occurred to me that if you wrapped the downpipes and the mufflers it might be as good at keeping driver's side temps down as undercarpet insulation (of course, the wrap would get shredded the first time you high-centered the muffler).
 
John Turney said:
Sounds like a Healey.
Click to expand...

Yup - I had a mild steel exhaust on it prior to installing and there's a negligible difference in sound - perhaps it's my brain playing tricks on me, but I feel like there's a slightly throatier tone to the new exhaust, but that could be the dollars I spent on it talking! :greedy_dollars:
 
RestoreThemAll said:
From a March 2009 Randy Forbes post
"I do not recommend wrapping your exhaust (assuming tubular headers) with an insulating wrap. A thermal barrier coating, applied inside and outside is a much better solution, and the headers will last A LOT longer.

The wrap may show immediate benefits, but it will soak up water (leading to rust) and will also fatigue the metal by subjecting it to intense heat that it cannot dissipate. Your wrapped pipes will live a much shorter life."


I guess I won't be wrapping my manifold or pipes.
Click to expand...

I guess I won't be wrapping my manifold or pipes.

GOOD:
:iagree:
 
Keoke said:
I guess I won't be wrapping my manifold or pipes.

GOOD:
:iagree:
Click to expand...


I usually defer to Randy, but my experience differs. I wrapped my BJ8's downpipes years ago and have not experienced those problems. For starters, I sprayed the wrap with the DEI silicone coating--good stuff--and the wrap is all but waterproof. The pipes get pretty hot, even with the wrap, so any water that gets past the coating is quickly boiled off. Can't speak to the fatigue issue but I probably have at least 30K miles with the wrap with no issues. IIRC, I had the pipes off at about 10-15K miles and saw no evidence of fatigue.

Agree the coating is the ideal solution; when I rebuild the engine I will probably get the coating on the iron manifold but, unless I see serious signs of metal fatigue I'll stick with the wrap on the downpipes.
 
I did some internet 'research' on the topic, and the concerns seem to be threefold:

1) The wrap will absorb moisture and cause rusting. I discount this because a) exhausts are hot; water doesn't hang around long and b) apply the silicone coating and it's a non-issue
2) The wrap will cause uneven expansion/contraction of the metal. Possible, due to the fact that overlapped areas would contain heat greater than the non-overlapped areas, though I doubt that the expansion would be that localized due to steel/iron's relatively good ability to conduct heat fairly evenly. It's not like the metal surfaces are being rapidly heated and cooled.
3) 'Super heating' of the metal will cause fatigue. This has merit, IMO, but I've seen unwrapped tubular exhausts fail regularly with no wrap (the tubular exhaust manifold on the otherwise robust Jeep I6 engine is one well-known example)

There's a lot of anecdotal evidence of the 'I wrapped my exhaust and it cracked, therefore wrap is bad' variety. There may be some merit but, as a statistician would say, 'correlation does not imply causation.' My opinion is that exhaust components are more likely to crack due to vibration than anything.
 
On collector cars that sit the wrapped exhaust does not get hot enough to burn off the moisture collected in the wrapping. If the car is kept dry and you take extra precautions, sure you can make it last. But to just wrap and go I would not expect it to not rust a steel system.
 
I tried wrapping a set of mild steel headers once and will not do it again. I race, so therefore I run at much higher revs with a lot of full throttle time compared to a street driven car. I didn't have an EGT gauge at the time so I don't know what the temps were but I suspect I was a bit lean at higher revs so could have been 1500 degrees or more.
My headers failed by the end of one race season (6-8 races and about 5000 miles street diving)- I had a crack. When I removed and unwrapped them I found large "blisters" (as much as 1" in dia.) all over the tubes, places where the tube walls were reduced in thickness by 1/2 or more. I didn't take any pictures unfortunately. I replaced them without wrap in 2005 and these still have no signs of problems.
I know my experience is 'anecdotal' but I am still convinced that the wrap was the cause of the failure. There was no sign of rust as others have said, the heat cooks the moisture out when it's running. However, for an occasionally driven street driven car I would worry about moisture during all the time the car sits in the garage. I also tend to agree that ss would be better able to withstand the high temps. the wrap will cause.
Just my expreience, yours may vary.
Dave
 
red57 said:
I tried wrapping a set of mild steel headers once and will not do it again. I race, so therefore I run at much higher revs with a lot of full throttle time compared to a street driven car. I didn't have an EGT gauge at the time so I don't know what the temps were but I suspect I was a bit lean at higher revs so could have been 1500 degrees or more.
My headers failed by the end of one race season (6-8 races and about 5000 miles street diving)- I had a crack. When I removed and unwrapped them I found large "blisters" (as much as 1" in dia.) all over the tubes, places where the tube walls were reduced in thickness by 1/2 or more. I didn't take any pictures unfortunately. I replaced them without wrap in 2005 and these still have no signs of problems.
I know my experience is 'anecdotal' but I am still convinced that the wrap was the cause of the failure. There was no sign of rust as others have said, the heat cooks the moisture out when it's running. However, for an occasionally driven street driven car I would worry about moisture during all the time the car sits in the garage. I also tend to agree that ss would be better able to withstand the high temps. the wrap will cause.
Just my expreience, yours may vary.
Dave
Click to expand...

Good to know; I will be sure to check my downpipes when I rebuild the engine (or sooner if I need to replace the exhaust). I drive my car 4-5K miles a year, but it's mostly highway/backroad cruising.

On another note, if you were to just ceramic coat the outside of the tubes you would, theoretically, get similar problems. Looks like coating inside and out is the best option.
 
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