Are all these heat shields necessary?

Adjusted the valves on my 964 this weekend. In removing the catalytic converter, I found that I had to remove a couple of heat shields that surround it to get at the four bolts on the intake side. Naturally, most of the bolts and clips that held these shields on had turned to rusted blobs making re-installation a chore. All you 964 owners out there, is there any reason to put these things back on?

Well I'm no expert on this but I've removed the underpan and most of the sheilding from around the engine. I asked this question awhile ago to my shop and they didn't really have an answer, pro or con.

How about a little verbage on how your valve adj. went? This is a project I'd like to do on my car myself, but as yet haven't got up the nerve.

Yeah, I definately run without the underpan. It's the shields around the cat. I'm uncertain about - one end of the cat. is pretty close to the rear tire.

The valve adjust. went ok. I read through all of the old posts at this site on valve adjustments and went into it with a pretty good idea of what to expect. To get at the lower exhaust valves on a 964, you have to remove a lot of crap (sec. muffler, cat., assorted heat shields). Nearly all of the bolts that holds this stuff on had degraded to a point where they had to be snapped or ground off. This part took longer than expected.

Adjusting the valves went exactly as expected. Access to the lower valves is great (once everything is off) making them easy. The upper valves are a *****. It's all done by feel because you can NEVER really see what your doing. I'd recommend doing all the lower adjustments first until you develop the "feel". Then go on the upper. #6, all the way forward on the right side under the power steering unit took me about as long as doing all the other adjustments combined. Getting the feeler gauge into the gaps is tough, but I did find that after a while, I got better at it. Looking through some of the old posts on this, I noticed the approach some people took was to back out the adjustment screw to create a huge gap, then tighten it back down on the gauge. This would probably work, but the downside is that you'll probably find that most of your valves don't need any adjusting. In my case, out of the 12, I made an adjustment on 6 (5 seemed a bit loose and 1 a bit tight). The adjustments I made were TINY.

Looking back now, I'll certainly do it again. It took me about a day and a half but I'm sure I could cut this in half next time. Good luck.

I too removed my heat shield surrounding the cat on my SC. I was concerned about the same thing you are....seems too close to the tire....
Well, 20K later and I haven't had a problem.
mine was cracked and made an aweful clanking noise until I ripped it off. Some people might tell you that it could lead to premature tire failure due to the heat coming off of the cat. It would be interesting to use a heat gun and take readings off of both rear tires and see if thee is a major difference in tire temp or not.
hmmmmmmmmmmmm....

Cats run hot; that's what they do to clean up the exhaust. The factory put shields on top and bottom to keep heat off of the tire and any combusible material you park over (dry grass, etc.).

If the engine misfires for any reason, unburned fuel exits engine, the cat then becomes much, much hotter and, in some cases, can glow red hot overheating everything around it, including the engine.

Sherwood Lee
http://members.rennlist.org/911pcars

hot cat= toasted lower plug wires. as well as grass fires.

Lose the cat.....

I think the reason for the shields is to stop heat from transferring to flamable objects (like a pile of dry leaves in fall). I think several lawsuits were filed against GM, Ford, and Chrysler years ago because people would park their cars on a pile of flammable debris and then find their car on fire minutes later. If you're carefull all the time, taking them off probably isn't a problem for you, but you may want to re-install them when you sell the car, or make it very clear (like in writing) to a potential purchaser that these types of risks exist.

Hope this helps,

Bill Wagner

On those heat shields... I've left the cat heat shields in place, cats get very hot! The shielding I removed was the silvery backed plastic shrouds from around the heads. My feeling on the cat sheilds, is that the cat is just to close the left valve cover not to transfer heat, especially in summertime stopn'go traffic...

Sorry, I couldn't resist.

That's what HeetSheets are for; to block cat heat from the engine. If you'll notice, the factory only has cat shielding top and bottom only. The engine valve cover is fully exposed to heat from the cat. Even without a cat., exhaust heat to the engine from the HEs (on my early 911) has reached 300 deg. F.

Sherwood Lee
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