ketel

Gang,

Due to a nasty rattle I removed the thin metal shield that lies between the secondary muffler and that tinfoil covered protective cover where the left bank valve cover/plug wires lies. Now that the thin metal heat shield (I assume it is a heat shield) is gone, can I just leave it off or will heat from the secondary muffler cause damage to the tinfoil materials and possibly the valve cover?

Thanks all.

ketel

Duck

Was it attached to the secondary muffler? I am trying to think of what heat shield is there except that is part of the muffler.

Jim Howley

I just replaced my secondary with a G-Pipe, and I didn't have a seperate heatshield either.

doruiacovescu

I would keep that. At high speed the secondary muffler becomes veryyyyyy hot.

ketel

It is a thin curved rectangular metal pan that's about 6" x 20" and curves around the right hand side of the secondary muffler. It is a separate pan but is secured to the secondary muffly by four bolts/fasteners.

ketel

tbennett017

I can't picture what you're referring to. My secondary has a "layer" spot welded to it that conforms to its shape, and is pretty permanently attached....

The other shield is part of the engine 'box' and is attached to the frame via 10mm bolts...

ketel

Does this photo help? It resides BETWEEN the secondary muffler and the tinfoil backed material that protects the left bank valve covers. The shield is held onto the secondary muffler with 4 10mm bolts.

crg53

I have never seen one of those, mine is like what TBennett017 said, spot welded to the muffler.



PS I hope you guys mean 6 m/m bolts, 10 m/m wrench size.

ketel

Yes, 10 m/m wrench.

Perhaps this is an '89-only config? Hard to believe but it's possible.

Either way, I don't want the car bursting into flames because of heat coming off the secondary muffler igniting or melting something, so I will probably have to get down under there again and re-attach it unless I get a strong vote from someone on this board to just leave the dang thing off. I prefer leaving off these heat shields as they just add weight, block air from properly cooling things, trap excess heat and add nothing to performance. In this case, perhaps might be better to leave it on. Thoughts?

ketel

xeps

As mentioned by the others, mine is also welded. Does your muffler have a date stamp on it? If I recall correctly, it should be clearly printed on the bottom of the the secondary.

I would put the shield back on, and see if it can be adjusted to stop the rattle.

I had similar rattles coming from the heatshields on my catalytic converter. Unfortunately several welds were broken, so there was no solid remedy short of welding it back together. While I waited for a cat bypass to arrive, I used the highest temp silicone gasket maker I could find to temporarily stop the rattling.

tbennett017

or maybe cut/spring washers under the bolts to help stop rattling/loosening.

Heat is a big deal, and I'd put it on... IMHO.

CT944

i'm a big fan of air flow, so if your engine tray is removed, i'd remove all those shields and just ensure all the spark plug wires are at least 1 inch from any exhaust pipes. i have a cat bypass and primary bypass and all heat shields and engine tray has been removed.

ketel

Yes, engine tray was removed years ago. The belief was that the engine tray did little to improve aerodynamics under the vehicle but what it *did* do was trap heat there and was believed to fry the valve guides in other 964s.

With this secondary muffler shield removed there is still that tinfoil covered heavy cardboard-like material that appears to be a heat shield or sound deadening panel of some sort that sits between the secondary muffler and the valve covers/plug wires. I hope that is the sufficient buffering you are referring to.

Since there seems to be a difference of opinion on this board, I will split the difference and try to go without the shield for a week or so and see if I notice anything difference wrt engine temps, etc. I might even pop the car back up on my floor jack to have a look. If I notice any heat-related warping or other damage, I will put the shield back on. Fair compromise?

ketel

CT944

Here's my motor. Been like this for years. I did make sure the spark plug wires were not touching any of the exhaust material. I had to use some wire ties to be 100% sure, but so far there have been no issues.

C24FUN

It looks to me like you're confusing the CAT with the Secondary. That heat shield in your picture goes between the CAT and the left side cylinder heads attaching to the mounting points on the CAT.You can see the mounting points in the engine picture in the last post. Probably a good idea to keep it if you want your plug wires to last.

Hope that helps!

Jim