Wrapped headers

[anonymous-user]

Hot weather again so under bonnet temperatures on my Monaro are higher than I would like. It’s always been a problem but I keep forgetting to do anything about it. One option is to get the headers wrapped or coated but the latter is a faff and can take ages.

Heard mixed reviews on whether wrapping exhaust headers is a good idea on a road car. Any practical experience or advice?

Thanks.

[anonymous-user]

wormus said:

Hot weather again so under bonnet temperatures on my Monaro are higher than I would like. It’s always been a problem but I keep forgetting to do anything about it. One option is to get the headers wrapped or coated but the latter is a faff and can take ages.

Heard mixed reviews on whether wrapping exhaust headers is a good idea on a road car. Any practical experience or advice?

Thanks.

Wrapped or coated headers can reduce local radiative heat problems, but won't make much difference on general under-bonnet air temps. The real solution is to make sure the hot air can get out, and that it can be replaced by cool air coming in somewhere. In certain cases, specific "chimneys" have been used to vent hot air off the exh manifolds and cats up and out the bonnet. In that case, the exhaust line is usually encased in a heat shield and the top of that shield vented up and out a suitable bonnet vent

[anonymous-user]

Note the four small rectangular chimneys

[anonymous-user]

Max_Torque said:

Note the four small rectangular chimneys

Clever, thanks. Any further details on the design? Are those simple tin heat shields that sit above the headers? I guess the chimney collects the heat and vents through louvres in the bonnet?

[anonymous-user]

Pericoloso said:

Are those "chimneys" an Aston part or added later ?

Std/OE parts

The header and cat assy'd are clad in the usual metalic (sand filled) formed heat shield material, and have the chimney stuck on top. When the bonnet is shut, hot air thermo-syphons up the chimneys off the mani/cats and out the bonnet vents and cold air is pulled in a matching set of holes in the engine undertray that align with the lower skirt of the downpipe cladding.

Stopping after a good thrash in a hot climate, you could easily grill bacon on the bonnet vents!

[anonymous-user]

ETA:

iirc, the chimneys were not carried on to any other Aston vehicle beyond the original Vanquish, as testing proved they were not actually needed. They were put in place on that car as a "just in case" because there was a concern raised about heat soak damaging the bonding glue used for the aluminium chassis. However, later test and measurement proved that the ally chassis was actually just as good at conducting away engine bay heat, so the actual bond temperature was effectively low enough to not be a concern.


( that's my memory of it, but bear in mind it's nearly 20 years ago now, so i might be wrong..... ;-) )

[anonymous-user]

Ok, thanks. So what seems like a cheap solution is in fact a rubbish idea so I’ll stay clear. I want to get a new intake fabricated so I might get a pair of heat shields added at the same time along with bonnet louvres.