I have a 94 Ford Ranger w/ the 4.0 V6.  The heat shield came loose from the catalytic converter about a week ago.  I have been meaning to go after it w/ some JB Weld, but never got around to it.

The girlfriend was driving the truck last night and when she came home she said "How important is that heat shield thing?  I was driving and heard a noise that sounded like it fell off and skidded on the ground.

Me: Did you stop and pick it up?

Her: No, should I have?

So heres the question.  If I don't have the heat shield on the cat. converter, am I going to ruin the cat. converter?  If so, how quick will it go?  

I checked w/ a auto parts store and you cant buy just the heat shield, you have to get a whole new converter which I don't want to do.  If I was to jimmy-rig it and make my own heat shielf for it, what should I make it out of?  Aluminum, tin....????

Driving without the heatshield is not gonna ruin the converter. The heat sheild is just to protect the bottom of the vehicle from the heat in the converter. I'd rig something up with tin. Screw buying a new converter.

I'm no mechanic but I think the heat shield is only there to prevent the hot CC from catching leaves and things on fire when you park over them. It probably also protects it from road debris that kicks up.

Slacker is right.  It's really NBD to be missing it, unless you have a habit of parking your truck in tall dry grass!  The shield on every vehicle I've ever had has eventually come lose, a big hose clamp around it is a good way to stop the rattleing, but then you don't have to worry about that!

I don't know much, but this I know.

It will NOT damage the inside of the convertor or take anything away from it doing its job.

If the truck is running fine,not too lean or too rich the chances of you starting a fire in tall dry grass is very very small.

had she touched it she quite likley would have suffered some burns unless you had a set of pliers in the truck (who doesnt?)

All I know is the 280Z's that had cats on them had a floor temp light to make sure you didn't start the car ablaze from an overheating cat. [devil]

Just buy a dynomax high flow cat, and a muffler while you're at it, and have 'em welded up.

I would go to a automotive salvage yard(aka junk yard, such as Pick-A-Part) and take one off another vehicle similiar to yours.

In case you were not assured before you have no problem.  Most heat shields are put on trucks to keep from causing fire when off road or in a field of tall grass.  My converter cover was loose so I bolted it back on, but other shields on the Y-pipe that just face the ground and are not near anything I have just taken off when they start to rattle.  

Cats are purposely made to get hot to promote the burning of hydrocarbons. The hotter the better. The heat shield is to protect external things (ex:floor pans) from the heat of the cat, not vise-versa.

FYI, A cat uses some elements as catalyst (pallidium and other crap) to turn harmful polluting compounds (Nox, CO, Hydrocarbons) into more benign elements or compounds.

The catylitic elements take a N from the NOx Nitrogen Oxide Compounds, forming N2 (Nitrogen is diatomic like Oxygen) and O2.
2NO => N2 + 2O2

These now free O2's combine with Carbon Monoxide to form Carbon Dioxide.
2CO + O2 => 2CO2