Well yeah with enough perfect insulation the engine bay temp wont rise at all and with the carb spacer the temp rise of fuel in the bowls becomes negligible

Of course insulating it that well would be quite a challenge. But every little bit counts and your not going for perfection you just need a small percentage change some places

 

Not really, it's just the angle of the picture. Here it is from the other side

 

I think we're entering fantasyland here? The heads and intake manifold are around 200 degrees after shutting the engine off, and there is an awful lot of thermal mass there, and even good insulation lets heat through over time.

 

One non insulator thing to check: timing. It may all be fine but worth checking your intial timing and, in particular, check to see if your vacuum advance is still working correctly. This can go a long way to decreasing exhaust temperatures to begin with.

 

I think he needs an IR thermometer and to do some experimenting. and fwiw Exhaust insulation has a dramatic influence on the temperature of items running around the engine bay. It isn't fantasy land - it is a requirement for the vehicles I work on, high output daily driver turbocharger application 500+ 1k 2k rwhp exhaust coating and wrapping and blankets are a must. I can perform a dyno pull on my car 600rwhp gasoline and then lay my hands on the downpipe shield right after and the engine valve cover is the temp of hot oil, not hot exhaust, but this isn't possible without insulation it would just melt everything instead

 

But how hot is it after 15 minutes?

 

Temp will depend on insulation , heating rate depends on the temps of surfaces, those in contact with.

more insulation = lower engine bay temps over time

If I plugin the equation I posted for you earlier and run it through say, excel to generate a curve showing temp over time, the max temp over time will be less and the temp increasing rate will be less as we added insulation to the conduction, convective, and radiative components of the equation. But I don't feel like doing all ofthat so lets imagine a simple example

say we have a steel bar thats been heated to 2000*F and we put it into a jar with and without insulation.
After say 20 minutes the bar with insulation will be higher temperature and the jar will be lower temperature than the one without

Insulating the bar slows down the change in temp over time
The fridge in your kitchen has some heavy insulation to keep it cool inside,
without that insulation your kitchen would be colder in a volume surrounding the fridge by some gradient T and the fridge would be warmer inside

Auto manufacturers insulate engine bays to keep heat inside for efficiency and economy, just like their engines, heat is energy not to be wasted. When that useful heat starts causing some issue the right way to think about this situation is, 'how can i re-direct that useful heat to something else?' and this is what the carb separator plate does and what exhaust wrap will start to do for it, you can also insulate many parts such asintake systems and water flow systems with plastic parts and panels and reflective surfaces and heavy thick walled exhaust tubes and heat shields that we frequently find

In reality we shouldn't really care about the heat in this case, because this is an antique preservation, reliability application, not an economy and daily driver app. So the EPA won't care and the price of fuel wont change significantly or noticeably if we discard some engine bay heat here. You could do with a cowl hood for example, just let it go. If you find some way to sink and release from the trouble'd bowl that would be fine , its why i suggested a heat sink