my brother used some of this wrap on an old jeep he is restoring. he said you can brush your arm against the exhaust pipe while the engine is running and it wont burn you. He used a black color wrap and it looks real nice. I'm probably going to do that when I get this point of my amphi repairs. their web sight is www.thermotec.com . I'm not sure if the wrap would be the proper product to put around the muffler, or if it would be better to use one of their other products. I figure i'll ask themotec when I get to that stage.
That makes no sense to us, would just trap heat, Amphicar is designed that heat is pushed out through the louvres above the muffler. A popular option here is a ceramic coating called Zircotec that really helps keeps temperatures down,
Muffler systems, and catalytic converters in particular, are often heat shielded for the very purpose of reducing radiant heat transfer to surrounding objects. That shield looks like it would serve the same purpose.
The paint on the underside of my engine hood directly over the muffler is blistered in spots and I was concerned about the color coat above so I wrapped the muffler and pipes. Better but the hood still gets quite hot. I may give that shield a try.
Zircotec is a spray on ceramic coating that you put on manifold (headers) it works much better than you expect. Wrapping the muffler also helps. Amphicar is all about stopping heat radiating in engine bay, very different situation to normal cars where shields are used to protect stuff in the airflow underneath. Wrong ignition timing can make the engine run much hotter than normal so always check that.
Fan pulls air through rad at block level and throws it around transmission which is important to cool down. That area should be sealed as air then rises and goes in the other direction and comes out through louvres so what should be hottest air (around muffler) gets out quickly. That's why car can overheat if back seat removed, the hot muffler air is then pulled down around carb. Transmission temp is important, at highway speeds it builds slowly to around 80c. Modern lube like Amsoil is fine at that and higher but not old dyno oil. Double lip oil seals in transmission go hard because of heat as much as anything else. Engine overheating should never be a problem. Fuel vaporisation is due to ethernol and gasses in modern fuel, these days need to insulate lines and ideally isolate carb from manifold heat, especially on 1147 where it's part of exhaust as well. Run fuel line direct from pump to carb - shortest route, not around front of engine, that was done to cool them in Triumph application. My dad and the Germans have done lots of measurements about this, short answer is Amphicar got it right first time. It's also important that radiator cowling is in place with correct rubber seals to back panel.
When one of my muffler systems was first built the shop moved the muffler too close to the firewall and it badly blistered the paint there. I had it rebuilt, moving it back to the correct position and repainted the firewall in that area. I suspect that the shield in the photo would move more heat against the firewall again and cause a similar problem. The factory system of getting the heat out through the vents seems like the best way to me.