9 replies to this topic

[Wirra]

I have just had a new set of extractors (headers) made up for my road-going 70s sports car. The car is fitted with a GM LS1 5.7ltr engine in factory tune (approx 235kW). I had intended to used exhaust wrap as the engine is a bit of a tight fit and I thought the wrap might limit heat transfer to the bodywork. I have been told the wrap will cause crystallization of the pipes.

I see the wrap used somewhat in historic racing so there might be some general interest.

What exactly is likely to occur? What steps should one take? Thanks.

[cheapracer]

Nothing will happen in the time span you will own the car, live free, go fast and stop thinking

FWIW I pour gearbox oil inside any chrome header pipes to stop "blue'ing" the external surface verifying that that also stops heat transfer (old British bike trick).

[h4887]

I have just had a new set of extractors (headers) made up for my road-going 70s sports car. The car is fitted with a GM LS1 5.7ltr engine in factory tune (approx 235kW). I had intended to used exhaust wrap as the engine is a bit of a tight fit and I thought the wrap might limit heat transfer to the bodywork. I have been told the wrap will cause crystallization of the pipes.

I see the wrap used somewhat in historic racing so there might be some general interest.

What exactly is likely to occur? What steps should one take? Thanks.

Are you saying the pipes are made of a non-crystalline material?

[McGuire]

Many header manufacturers do not recommend insulation wraps. Their brief: The wrap elevates pipe temperatures, promoting cracking, and traps moisture, greatly accelerating corrosion, especially if the vehicle is operated in hard weather where the pipes and wrap can get soaked down. I've seen cases where exhaust leaks developed in mild steel headers and when the wrap was removed, the pipe nearly fell apart with it. I've also seen cases with no apparent trouble, so environment might well be the difference.

Stainless and ceramic coatings will inhibit corrosion, but who wants to hide such pretty parts with exhaust wrap. For me, the problem with wrap is it won't look good for very long. It's essentially a fabric placed under the hood. It will tend to fray, stain, trap dirt and engine fluids along with the aforesaid moisture, and will be difficult if not impossible to clean. No matter how meticulous you are, it will start to look nasty in a year or two of regular use, though black will surely look better longer than the lighter colors. On the other hand, ceramic coatings are durable, have excellent insulating properties, and are easy to keep looking nice. Personally, unless I had a severe and specific heat issue to fight, I would avoid using exhaust wrap on a street car. My opinion.

[SteveCanyon]

+1 for ceramic coatings. Maybe not quite as good (maybe) but zero downsides and much more pretty.

[Lee Nicolle]

Ceramic coatings when done properly are very good, they stop corrosion inside and out and look good. And are fairly easy to keep clean. Though from a pure power perspective probably not quite as good. But as other have said they rust the pipes quite quickly and look crappy fairly quickly. But they hold heat.
A true story I have heard on a mildly modified big block Chev Duallie the exhaust pipes to the mufflers were also wrapped. They held so much heat the pipes sagged about 3" towing a race trailer Adelaide- Melbourne. They unwrapped them for the return trip and had to do some work to straighten them out again.
While not in favor these days the old trick of aluminium spraying works well to protect the pipes and seems to make it a bit cooler around them. I have seen a set of 30 year old extractors still useable on a restored Sprintcar, and another with a new set aluminium sprayed still look new after about 12 years. My recently aquired Cleveland ones still look good and are over 10 years old, though have been hanging on a wall for most of that!

Edited by Lee Nicolle, 28 October 2010 - 21:22.

[J. Edlund]

These days many car manufacturers use double wall pipes with an air gap insulation. Not quite as easy as wrapping the pipe with insulation, but done right it offers a long life and low heat transfer.

Another option is to wrap the pipes with insulation, and then wrap the insulation with metal foil and weld that to the pipes. Makes moisture and dirt stay away, but requires a good material in the pipes.

[Powersteer]

interesting with the double wall pipes, it can be very good to market given the right concept of todays customer selection for tuning pipes. cosmetic look on the outer wall acting as an insulator and high flowing hot pipe inside while maintaining long life. how about those wonderful looking multi-colour pipes from motorcycle tuners?

[Wirra]

I thank you all for your input. It looks like ceramic coating is the way to go.

[NeilR]

I have lost two sets of headers with wrap and will never use it on headers again.