Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Plus 4 cooling issue

I agree with Paul that if the heat is contained around the manifold, it will also be held in the head, around the exhaust ports in particular.
The 2L Duratec has the cat under the wing, and the wing gets very hot above the cat. That's why I fitted an insulting jacket around my cat to keep the wing cooler. It may be possible to fit a second heat shield over the top of your cat (with space between) to prevent heat radiating upwards. Having the inlet pipe directly over the top will increase air temp significantly, and the narrow bore looks quite restrictive.

A cast iron manifold will possibly suffer cracks due to repeated heat cycles affecting the microstructure and what is known as "growth of cast iron" then occurs.
Not much effect occurs below 400 degrees C but it increases as temperature rises above this.
With stainless steel manifolds it is not such a problem though, which is one reason why they are preferred for high output racing etc..(see the headers glowing in some Youtube videos!).
Keeping the heat IN the cast iron will enable the growth to be occurring so insulating a cast iron manifold is not really a long term method.
Ceramic coating does not have a huge insulation effect but does reduce radiant heat out into the engine bay thus of benefit.
Protecting sensitive components/areas is probably the best solution as it removes the insulation effect on the cast iron.
Hence the suggestion to insulate the air inlet system or even re-route it if practicable to both improve cold air intake and reduced heating of that air.
Perhaps a heat shield to shroud the manifolds(s) with ducted air to purge the air away would help?
DaveW's suggestion for insulating the cat will also have the benefit of getting it up to effective working temperature a bit quicker too.
It's a bit of a compromise between insulation and shielding to keep heat where it's of benefit and shield areas away from it if it's detrimental.
Each car/engine set up will require a bit of thought to achieve these two things.
For my Plus8 I have to consider shielding the manifolds and creating an airflow to purge the hot air, and getting a supply of cool air to the filter as possibilities as under bonnet area does get warm! If the filter box reaches 40 deg C in cool ambient temps then it's worth trying some simple shielding etc..
The car does not overheat though the fan does kick in when on stop and the heat builds near the fan switch.
In the end, how much actual effect on performance will this have? It won't be a huge amount with the standard cast manifold and exhaust.
If I was going into competition then its a route to consider seriously as every little increase will benefit cumulatively with other tweaks (engine mods/weight/mapping/aerodynamics etc.).

I'm really not sure how much the hot air from the cat. affects the intake pipe above it, as, although it will get the hot air, it is drawing fresh cold air in directly from the nose of the car, and this will actually cool the pipework so the air going into the engine will not actually be traveling slow enough to get that hot, slightly warmed over, maybe, and obviously not as dense as completely cold air, but I doubt it is measurable from the driving seat. A simple aluminium shield above the cat. would also help, of course.

I came in a bit late on this topic but I have a cat that is a long way from the engine, under the running board in fact, plus I have exhaust wrap, despite Chunky's misgivings. Because the cat is so far from the engine it was decided to use wrap to get it up to temperature as soon as possible, and keep it there.

Despite all that there are times when the under bonnet area still gets very hot. I have had it so hot that the bonnet catches were almost to hot to touch. The engine temperature itself is usually 90 to 95 degrees, sometimes rising to nearly 100 degrees. Intake air temperature rises to over 40 degrees acording to the Omex logging software.

With an OBD 2 reader such as Torque you should be able to read the intake air temperature.

As promised, here's a few notes on my attempts to reduce under-bonnet heat. The manifold is wrapped in Kevlar-backed insulation (avoid the cheap E-Bay stuff. I got mine from a Company called Agriemach - no connection) held with stainless jubilee-style strips. Not aesthetically very pleasing but should obviate the problems which have been mentioned connected to tightly-wound manifold wrapping. Belt and braces I used light alloy expanding ducting (roughly 3.5 inch od very cheap from diy stores -- it's used to exhaust cooker hoods) on the air inlet pipe which I had previously noted was getting hot. I sealed the ends with 90mm id adhesive-lined heat shrink. Probably many sources but I got mine from Rev Tec (no connection). Went for a stimulating 40-mile blast today and I'm convinced the underbonnet temp is far lower and the bonnet stays, held by clips along the bonnet hinge, were hardly warm. Previously they almost burned my fingers.
pip pip

One more pic

That looks really good. Do let us know if you think it has worked and improved things, and maybe increased power too, after you have done some long runs and had time to properly evaluate it.