Header wrap or Jet Hot or ceramic coating
 

Have you wrapped or coated your exhaust manifold / header? What was the result? The product manufacturers boast of lower under hood temperatures and increased power.

Re: Header wrap or Jet Hot or ceramic coating
 

The wrap keeps the exhaust gas hot and for some reason this helps the engine performance. I think it helps with the scavenging somehow. Perhaps preventing a standing wave in the exhaust that reflects the pressure wave back up to the exhaust valve. Or it could be the hotter exhaust gas is less dense and flows easier. I don't know. The secondary effect is keeping the engine compartment cooler but I don't think that is the primary objective.

Re: Header wrap or Jet Hot or ceramic coating
 

I have wrapped headers and pipes before and never noticed an increase in performance. Definity helps with heat.

For a standard Model A I don't see the cost and effort paying off.

Maybe as NK mentions about gas flow, in high HP engines it could help with the exhaust gases.

Re: Header wrap or Jet Hot or ceramic coating
 

You want the manifold to cool. Wrapping it might lower temperatures under the hood, but might cause unexpected heat issues. They warp now!

Re: Header wrap or Jet Hot or ceramic coating
 

The exhaust wrap can trap moisture. If you do wrap it make sure you do not park it with the wrap wet.

I learned that lesson the hard way on an old Jeep I had

Re: Header wrap or Jet Hot or ceramic coating
 

Waiting for someone who has ceramic coated a manifold ! IF you could seal off all of the heat would you now get carburetor icing ? I had an inline 6 that the heat riser was rusted stuck and at times the icing would choke the carburetor, stuck along the road and opened the hood and watched the ice melt, resumed my trip after a couple minutes. I eventually free up the valve and no more issues!

Re: Header wrap or Jet Hot or ceramic coating
 

The stock Model-A engine uses too large of an exhaust valve to really improve scavenging by wrapping. If you want to improve scavenging, then consider using a set of step-headers that are wrapped, ...but again, for the size of the intake valve and the volumetric efficiency you can get, you really don't have a need to scavenge.

Lowering underhood temps can most greatly be improved by using engine pans which will force most of the frontal air going thru the radiator to exit out the hood louvers and some out beside the transmission.

Re: Header wrap or Jet Hot or ceramic coating
 

Mike in Milwaukee, You are correct that you don't want to run the cast iron manifolds hotter. I don't think anyone will wrap the cast iron manifold, but I could be wrong. I think the discussion is about wrapping the tube type headers. They don't have the warping problem that the cast iron manifolds do.

I don't think anyone will notice any performance improvement by wrapping the headers. That is unless you are building a racing engine.

Re: Header wrap or Jet Hot or ceramic coating
 

I have 2 A's, 1 with an original manifold and 1 with a ceramic coated one. If I idle them for the same amount of time the ceramic one is definitely slower to heat up. Once they are both at running Temps I'm not sure if there's a huge difference.

Re: Header wrap or Jet Hot or ceramic coating
 

As a follow-on to Brent's comment I'll add that I just added engine pans to my late '31 68C earlier this week after driving without them for more than a year. I realized an INSTANT drop in heat coming into the cabin...it was like night and day....far more evident than the under carpet insulation I added last spring. Had I realized how effective the engine pans are at reducing cabin heat I would have installed them long ago.

Re: Header wrap or Jet Hot or ceramic coating
 

Thank you all for relating your experiences.
As the Wretched Roadster
1. has her engine pans in place, and
2. I don't want to increase the probability of warping the exhaust manifold by wrapping it, and
3. ceramic coating's benefit is only apparent when first heating up, therefore
4. I will do nothing. This will not increase the weight of the vehicle, nor cost money, nor take time. Whew. Now I can focus on the many other things calling out to me.

Re: Header wrap or Jet Hot or ceramic coating
 

Wraping usually causes problems over time, warping, cracking.
Ceramic coatings definitely keeps things cooler under the hood plus the added protection
against rust. And it looks great.