TR2/3/3A Using header wrap on a street car?

[karls59tr]

I have read that wrapping a header actually damages the the steel on the header pipes because they don't get a chance to cool and the wrap does not really do anything to keep under hood temperatures down. I have the metal heat shields under the SU's to keep the heat away from them. So do I need to bother installing the header wrap? I am running an alternator and the front header exhaust pipe is really close to it so I may just wrap that area to protect it if does help keep the heat away in some way.

 

[Hamish Racing]

Karl
I wrapped my headers. Despite the horror stories. I think it affected poor quality mild steel from the 1970’s.
l have a stainless system now that will see me out.!!

i also made an alternator heat shield and covered the Ali with exhaust wrap material

no issues to date.

 

[karls59tr]

Karl
I wrapped my headers. Despite the horror stories. I think it affected poor quality mild steel from the 1970’s.
l have a stainless system now that will see me out.!!

i also made an alternator heat shield and covered the Ali with exhaust wrap material

no issues to date.
View attachment 97574View attachment 97575

I like that heat shield for the alternator. I think I'll make a similar one.

 

[mctriumph]

The only negative on header wrap(IMHO) is IF fuel is spilled on them at temp, instant fire.
So no drippy SU's allowed.
Mad dog

 

[JHaydon]

Lots of road cars had wrapped exhausts from the factory back in the day (I'm talking 1930s-50s, using different materials and construction). Yes, thermal wrap does help considerably in keeping underhood (and above-exhaust) temperatures down. I've run with and without on the racecar. Unwrapped nearly set the fiberglass bodywork on fire. The wrapped exhaust didn't even soften the adhesive on the decals.

My understanding is that the #1 problem is that a heavy, tight wrap will restrict the tubes from expanding as they get hot, which creates stresses. I also agree with Hamish, the problem is likely to be more acute with low-quality steel. I don't know if wrapping a tube that has had a few heat cycles might be better or worse, or if an already corroded pipe might be more susceptible.

There are now looser-fitting "sleeves" on the market that are supposed to allow the tubes to expand and contract happily (and presumably "breathe" if any moisture gets in). There are also spray sealants that you can apply to keep spilled fluids from soaking into the weave. Or you could double-up with a metal heat shield or aluminized blanket over the manifold. (I sell all of these products if you can't find a source.)

 

[TR6Quebec]

Wrapping the headers can be divisive. Focusing on wrapping the area near your alternator for protection sounds like a practical approach.