Found out today that there is a reason why Nissan chose to place heat shields on the exhaust side of the engine compartment.

 

Was doing some routine maintenance & cleaning under the hood and moved a nylon vacuum line I had routed poorly near the heat shield that protects the brake master cylinder area, and .... it crumbled like a 4000 year old scroll from king tuts tomb.  Checked the line and it had turned very hard and brittle on the unprotected side of the heat shield closest to the exhaust manifold.  On the other side of the heat shield, it was fine.  The rubber section of the line was fine.

 

Fortunately, I had coiled some excess & tucked it behind the MC so was able to cut it back & reconnect to the rubber section of the line.  I will extend the rubber section so that the nylon line is far enough away on the other side of the heat shield.  The nylon line has been in there about 4 years.

 

I always thought that the shield mainly kept the fluid in the MC from cooking, but it probably protects the plastic reservoirs as well.

 

(the nylon vacuum line came with and connects the Autometer Boost / Vacuum gauge that I installed where the clock was)

 

Maybe I will swap in the turbo motor one day to get some use out of the boost side of the vacuum gauge....

I have some of that foil covered bubble wrap hanging and placed in strategic spots in the engine bay.  My HEI module swap was getting kind of hot (I mounted it on the fenderwell, line-of-sight to the exhaust manifold) so I hung some insulation from the edge of the manifold just to test.  It works well, reflective and insulating, and the base materials have a temperature rating of about 230 F.  It's still there.

I knew those were there for a reason. 

When I put my header on I had to trim around the middle runners to get it to fit, glad I did.

 

interesting... i pulled all my heat shields when i put on the header thinking that it would run a lot cooler in that area w/out the big cast iron lump. 

i'm pretty sure i kept stuff from sitting over the headers, but i'll have to check my hose routing again though...

Nice headers and mod to the heat shield.

 

The small heat shield that protects the pcv hose is important as well.  Without it, the hose will get cooked.

Had a friend who did that, he put the shield back on.

my pcv hose was cooked when i got the car in stock trim - with the heat shields in place. i bought a new one and wrapped it in foil faced hose insulation and it seems to be doing fine.

i'll have to keep an eye on it though, as the cooking may be an issue over time. in general, the engine bay seems a bit cooler with the ceramic coated header vs. the stock manifold - this is just anecdotal from my working on it, no measurements taken...