I30tMikeD

iTrader: (8)

I am taking off my Cattman headers and putting back on the stock manifolds. I am wondering how important it is to put the heat shields back on. I know it can't be good for under hood temps, but I am going to have a turbo under the hood soon as well and that will be creating plenty of heat anyhow.

Any thoughts on how important it is to pu the heat shields back on?

optimus310

iTrader: (1)

I don't think the front one is so important, but the rear one has almost no ventilation, and is very close to other engine components. You should atleast wrap it on some header wrap.
BTW: TURBO!!!!!!!

I30tMikeD

iTrader: (8)

Yhea, I bought the turbo stuff Neal had for sale after he wrecked his car. It will be a few months before I have everything installed. Still need a few parts to finish off the kit. Already sold the Headers, JWT ECU, and MEVI. Going back to stock until I can install the turbo

http://forums.maxima.org/showthread.php?t=352710

NmexMAX

iTrader: (22)

As far as putting the heat shields back on, it shouldn't be much worse than with the headers, as Dave B stated that the cast iron stock manifolds retain heat instead of emmiting it like as the headers would do.

Stephen Max

iTrader: (59)

If you are running an intake pipe over the front header, you definitely want to have the heat shield in place.

I30tMikeD

iTrader: (8)

Good thinking Stephen. I will be running my intercooler piping right above it, although it is the hot side. The front head shield would be the easy one to put back on anyhow. It is the rear one I was worried about.

Stephen Max

iTrader: (59)

Yeah, that one was a b!tch to take off when I did the header install. If for any reason you are going to remove your intake manifold, that would be the time to put it back on, since (I think) it will be easier to access the heat shield mounting bolt holes in the top of the header from above.

Dave B

I wouldn't worry about the shields. The headers give off a ton more heat than the cast iron manifolds. My front manifold heatshield fell off years ago.

I30tMikeD

iTrader: (8)

Intake manifold has been off for a week now, car has not been driven for a while. I am going to try and remove the headers using that approach.

Any tips on removal? I don't have much expierence with header removal/install since they were put on while my motor was out over the summer. I am hoping that having the manifold off will do the trick and I won't have to remove or unbolt the cross member.

deezo

iTrader: (3)

Mike,

While you wait for the Spring to come, send the pipes out for Jethot coating.

http://www.jet-hot.com/pages/headercoatings.html

Stephen Max

iTrader: (59)

I seriously doubt you will be able to get to all of the header nuts if you don't remove the rear engine mount bracket. I'd go ahead and pull it off. It might take 30 minutes to do, but it will save you a lot of aggravation. Also remove the steering rack cover. Having the IM off will make getting at the upper nuts and the egr tube a lot easier.

stephenlc

iTrader: (1)

get the headers ceramic coated if you don't drive your car and that way you don't have to worry.

SPiG

iTrader: (7)

for ceramic coating

http://www.swaintech.com/race.html

MrEous

iTrader: (11)

Can someone explain to me how one metal would emit more heat than another? It was said that the cast iron would emit less heat than stainless steel. How is this?

Cast iron is known to be a better heat conductor than stainless steel...cast iron is also thicker giving it more 'thermal momentum'. (thus making it hotter, longer)

Just curious really...I am no physicist.

-maybe I can get my friend with thermal couplers to do an experiment. My headers vs his heat shielded stock headers.

NmexMAX

iTrader: (22)

Heat capacity, specific heat etc.

Imobejoas

iTrader: (1)

I took thermodynamics before, but that was like four years ago. I think I forgot everything... Heat conduction and heat transfer are two different things. This can be seen in CPU hsf combos. A good one will have a copper base because it transfers heat from the die really well. It is then melded together with aluminum because it dissapates heat better than copper.

So taking this concept into stainless steel and iron. Iron can probably soak up that heat better, and so it will act as insulation so thereby emitting less heat. The steal can probably dissapate it better so would emit more heat.

Stephen Max

iTrader: (59)

I wish I wasn't so busy at work, since this is a subject that I would love to talk about.

But consider that there are two scenarios. One is the steady state situation such as during cruising or driving in which power output from the engine is fairly low, and the other is a transient situation where you are making maximum power but over a fairly short time.

In the steady state scenario only the thermal conductivity of the material matters. For a given exhaust gas temperature, the header made out of the more thermally resistive material will have a cooler surface temperature.

In the transient case the material specific heat and mass of material (density and thickness) come into play. In this case the header with a higher heat capacity will have a surface temperature that will heat up slower, although the final temperature is still determined by the conductivity and the time constant of heat transfer relative to heat input duration.

2 Da Max

iTrader: (2)

paint your heat shield red

Broaner

iTrader: (10)

Very nice info.

I would leave it on because cooling the exhaust is not a good thing, the rusty iron manifold looks like @ss, and it will heat up the charged piping. The manifold and steering rack heat sheilds are the only ones I still have on my car. All the rest are totally useless in N/A applications.

I30tMikeD

iTrader: (8)

Got the headers off today. Was able to do it without removing the rear engine mount bracket or the steering rack cover. Only thing that was off was the intake manifold.

MrEous

iTrader: (11)

When we installed my headers we were able to do it all without removing anything but the Intake Manifold. Some tight places for sure.

It's harder getting the stock header bolts off/on than the aftermarkets due to bulkiness.