exhaust manifold heat shields

[mmdog85]

in the process of rebuilding l 98 and i need some info has anyone ran this engine without the heat shields, mine are beat up i was thinking about powder coating them and the manifolds any sugestions would be appreciated thanks

 

[Redbob]

The heat shields reduce underhood heat, make the sparkplug wires and plastic parts live much longer, and it's very doubtful GM wouldn't have put them there if they weren't needed. You do want nice shiny aluminum-colored shields that will have a low rate of radiative heat transfer ("low emissivity").

If you're thinking about powder-coating yours, or the manifols, think again: powdercoat won't hold up to the temperatures these parts see, especially not on the manifolds!
Regards,
R

 

[mmdog85]

thanks for your help Red i thought the same the shields are there for a good reason . Im wondering if a good heat resistant paint will clean the shields and manifolds up or just buy new shields

 

[Corvette-Pilot]

thanks for your help Red i thought the same the shields are there for a good reason . Im wondering if a good heat resistant paint will clean the shields and manifolds up or just buy new shields

What about the spray paint used to repaint the BBQ?
I would think flames are as hot as you are likely to see (hopeful not).

Just an idea?

 

[Redbob]

thanks for your help Red i thought the same the shields are there for a good reason . Im wondering if a good heat resistant paint will clean the shields and manifolds up or just buy new shields

Ah, the light dawns! Now I understand!
Yes, a good aluminum-content high-heat paint would be an excellent solution.
NOT black bar-b-que grill paint!
You want the high heat reflectivity of the aluminum coating.

 

[ArtZR1991]

Actually, you can powder coat if you wish. It is commonly done on race engines, where the manifolds get red hot. Even a shiny aluminum should hold up fine. I had it on my 383 stroker for 15,000 miles and they were perfect. The trick on manifolds, if you want to gain something a bit more than just looks, is to have the inside of the mainfold powder coated. The shiney, smooth interior keeps the heat in the exhaust gases, and lowers the underhood temps quite a bit, Jet Hot Coatings is a good source. They have several shops around the US, are quick and cheap. They do a lot of automotive work, and also do a lot of Navy work, powder coating gas turbine parts, among other things.

By the way, if you powder coat, be careful to tape pver gasket surfaces prior to the coating. They will thus not be coated. The stuff is so slick that gaskets will not seal well. In addition, if any welding is required to reinstall afterwards, cover that surface as well, as powder coating cannot be welded.

Another very good idea is to powdercoat the intake manifold inside and out. It really resists heat coming from the oil gallery lifter area, and helps performance. Just be careful to not coat the gasket areas (water, carb, etc). But it really looks good.. forever. Here is a pic of my 383 with about 3 years on the powder coat, and no polishing or cleaning other than soap and water.

,
or try this page for other pics
http://www.cobra65.org/hardcore99.htm

Cost to do this is in the couple hundred range, and takes about a week, with shipping. I guess you can tell, I am a great fan of Jet Hot. Of course, powder coating of exhaust is normal for Cobras, but it should really be considered for it's performance enhancements as well.

Regards,


PS Edit....
The pure aftermarket small block Bow tie 383 in the links above was built about 15 years ago, though the pics are in 2000. The car was a very successful bracket racer, and a lot of the build up issues are discussed on that link. It is so similar to the L98 you might enjoy reading about it. There is a lot about cam selection, ignition, machining, oil control (blueprinting the pump), and valves, etc. The guy that built this engine was in Ohio in the mid '80's and he was a master of the small block Chevy. After retirement, that engine did a super job as a street/show engine for many years. It is now back out of retirement, and with a new road race suspension (rather than the drag suspension) is road racing out west. If nothing happens to it, I hope to have it back in a couple years.

Hope the write up is of some help to you with your L98.

Obviously, I think more of powder coating than the other posters, especially versus paint, but I agree wholeheartedly that you really do need the heat shields, especially in a modern, crowded engine compartment like the C4.

Again, regards,

 

[Redbob]

!

The shiney, smooth interior keeps the heat in the exhaust gases, and lowers the underhood temps quite a bit, Jet Hot Coatings is a good source.

Not to put too fine a point on it, but if the coating you're talking about comes from Jet Hot (or HP Coatings), it's not "powder coat", it's a flame-sprayed ceramic coating, something ENTIRELY different.
Kinda like the difference between latex house paint and the heat resistant tiles used on the space shuttle...
Powder coats absolutely will not work on exhaust manifolds or anything that see more than perhaps 350 - 400F.

Needless to say, the Jet Hot coatings work just great anywhere in the engine compartment, especially as you suggested inside the manifolds - keeping the heat INSIDE an exhaust manifold or header makes it last far longer, since you avoid the loss of strength that steel or iron experience when they see exhaust gas temperatures.

But Jet Hot coating your heat shields is just plain overkill, and way more expense than you need.
Unless of course money is no object, in which case - fire away

 

[ArtZR1991]

I see you point Bob, but I wiould point out that the term "powder coat" is used to generally mean both types. So you are right that I would be referring to the ceramic based type, as opposed to the other varieties.

As to cost, again we agree that the shields by themselves would probably not be worth it, however, if one were coating the more important pieces, such as the manifolds, the smaller shields are essentially free (when I had mine done a few years ago, I had some smaller pieces just "thrown in").

As a whole package, the expenditure is rather small, and the benefits great, including performance, heat reduction (including the shields), and a lifetime of good looks without deteriorating. Its a good bargin relative to other things you could spend a similar amount on, but only if you are doing the manifolds.

So I think we agree?