Cheramic Coating On Headers, Good Or Bad..?

Not sure how it works or holds up over time, but you figure thousands of exhaust parts are coated daily across the world and I have never heard bad stories or reasons not to coat them...

 

The OP is correct in that stainless steel has a significantly higher coefficient of expansion than mild steel. I have seen these coatings on stainless flake off after some time first hand. That being said I would still coat them anyway, but I would use the black coating as it seems to be more resilient than the silver stuff.

 

Good - I have a silver ceramic coating on my stainless STi headers and it's survived flawlessly for thousands of miles, all summer all winter. I put the same stuff on my 355 headers, inside and out.

 

Ceramic coating is fine, no probs at all, and lasts well. HOWEVER... ceramic coating on it's own APPEARS to be insufficient to prevent the alternator in a 355 from getting too much heat. I think that time will tell, and maybe alternator heat shields are the easy solution. I think it was jetfixr who had one made out of the inconel used in the rear section of a jet engine!

I'm told that replacement headers in the same design as OEM but made of stainless (not mild steel) and made well (not by Mr Blobby the welder) are in the pipeline. Included in this design are full heatshields. By same design I mean 4-2-1, not 4-1. The rationale is that 355s are low enough on torque as it is, and losing any of it is not the best option. The 4-1 headers I had on my car gave me an extra 20hp, but at the cost of low down power. Anyway, the new ones are apparently designed for longevity and quality rather than outright performance - the 4-2-1 design adds a few $$$ however. I know nothing more than that, but will share anything I find out.

 

Um, factory headers are stainless already, its the wall thickness of the stainless that is changed with the after market ones (thicker=more reliable).

Anyone noticed how the pipes on a 550/575 get longer as the car gets driven hard. the expansion is amazing!

 

Search for and read through the thousands of posts on the Fabspeed Group Buy thread. You will also see pictures of my Not-So-Fabspeeds after maybe 40 hours of use. Uncoated and unwrapped as an experiment.

Coating, wrapping or preferably both is an absolute. For both radiated heat and technical (scavenging) reasons. With these headers naked you WILL cook the alternator and as well many other expensive trinkets in the immediate area.....motor mounts, AC compressor, etc etc etc. Coating will be far less expensive than the baked trinkets.

Think of it this way......why are the OEM manifolds shielded????

Read the thread and you may think twice about the Fabspeeds. When I bought mine I immediately picked up on a problem as I was unwrapping them and that problem alone should have made me immediately realize that these are NOT an "engineered performance solution" but rather a mass run of mandrel bent bright and shiny bobbles that will attract hungry enthusiasts looking for a suitable OEM replacement.

The problem........on the manifold collars they did not relieve enough material so that you can get a socket or in the least a box-end wrench on the mounting nuts. This is a HUGE oversight and makes in-car installation a pain in the backside like you can't imagine.

We design and fabricate mild steel headers every day for EVERY make of car and performance head that you can imagine and the FIRST consideration is the dimensioning and relieving on the collar to allow for tool clearance. Fabspeed didn't even take into consideration this first BASIC step which would lead me to believe that they had never even tested these headers for technical performance (installation) and actual engine testing for dyno performance results.

Maybe I should be as forward to post a picture of the headers laying on my used parts heap beside my Tella-Tubi silencer.

If you put any header into the engine bay of the 355 you need to shield many trinkets and I would recommend this even if the headers are coated or wrapped or both. I would not recommend a naked header and particularly if you are doing so only because you love the wonderful shiny appearance because it ain't going to stay that way anyway. I'm now running our own custom designed wrapped mild steel headers which in all rights are disposable each year when I yank the engine out. This is predetermined, calculated and acceptable to me. They aren't pretty and this too is acceptable since they are FUNCTIONAL and I place function before form in the engine bay of my 355.

Read the previously mentioned thread and then choose carefully. Good luck!

 

FYI. I you look in many of the Hod Rod parts catalogs there are several companies that make inexpensive (< $50.00)alternator/starter "blankets" comprised of a mylarized-heat resistant flexible material which has a velcro closure on it to adjust for size. In addition, they come with several stainless steel "wire ties" to wrap around the "blanket" to ensure it won't come off. They are supposedly resistant to aproximately 650 F. I used them on my 308s and 328 (euros), which also come with non-insulated OEM headers, along with the factory heat shield. In these cars, the alternators are even closer to the exhaust headers - No heat problems. I am planning on doing the same to my F355 when I perform my next 30K Major, re-builld my alternator, etc........ Might be worth a try.

 

Absolutely correct! Even with coating the alternator is GUARANTEED to bake and die. That will be a $1040.00 lesson (parts only) whereas you can apply a $20.00 blanket / shield and drive with a clear worry-free mind. There are many inexpensive "blankets" and "insulating boxes" out there. Funny enough....the best place to find this stuff is in fact in hot rod magazines. These guys have been doing this stuff for decades! Us exotic owners to a certain extent think that the exotic manufacturers would have covered off such issues since we are paying a big buck for a well-engineered machine........BUZZZZZ.....wrong answer! You make one change to an exotic you better be looking for the collateral issues that you will effect as a direct result of your change.

Here's a cool site: http://www.heatshieldproducts.com/

Buy, apply, drive!

 

Air gap is the key with heatshielding, wrapping some blanket material is far from the optimum, Jetfixr shows good thinking process with his.

 

Oh, and black is a great 'radiating' colour, silver reflective, I know my choice for headers.

 

I realize that it seems counter-intuitive, but if you have a reflective wrapped-object which minimizes ABSORBED heat from an external source, it will remain cooler than if not wrapped. I also realize that wrapping causes the alternators own internal heat to be retained, but it does have its own cooling fan and this increase in heat is minimal in comparison to the amount of heat which it absorbs from the exhaust headers. I used a laser-aimed infrared "thermometer" to measure the temperature of the alternator of my 1989 328 GTB (euro, with non-wrapped factory headers) after 10 min. of idle. Yes, I know its a 328, not an F355, and there is no airflow around the alternator, but it was the best semi-quantitative experiment that I could think of at the time. Off the top of my head, I found an approximate 65 F DECREASE in the body temperature of the alternator that was wrapped and factory shielded vs. the alternator that just had the factory shield. I'll check my notes when I get home and re-post if this figure is incorrect.

 

Brian:

IMHO the best color(s) for a coated header would be: black EXTERNAL to keep heat IN the headers and silver INTERNAL to keep heat from being absorbed when the exhaust gases pass through the header pipes. I realize that this is probably not possible, so I would pick black to keep the heat in the headers. I would rather "heat-soak" them, then the surrounding engine parts. ...just my 2 cents worth. But, hey, I'm NOT an thermal engineer.

 

Your 65 degree C must be nearly spot on!!!! Don't dig through all those abandoned notes tonight. The difference in alternator casing temp was a delta of 59 degrees C on my 355. My experiment set up was with naked headers (no coating no wrapping) and I shot the alternator with the thermal gun from under the car and half way up the casing on the outboard side. It's a pretty tricky area to get at. Nonetheless, I then install my homemade thermal shield box which provides a very nice air space around the casing and once again brought the car up to "fan cut-in temp" and re-measured the casing temp at the very same place. The difference of 59 degrees cooler just blew my mind. I had to check it 3 times to make sure of what I was getting and then redoing the math. That 59 - 65 degrees is the difference between life and death for your alternator.

My homemade heat shield box was constructed from the heat shield insulating material affixed to the underneath of the OEM muffler heat shield. When I install my GruppeM air box it comes with a heat shield to replace the OEM so all of the OEM shield material got either sawed up or cut up and found a new life in many places of my engine bay! Now that's what I call recycling!!!! Always remember, save a tree, eat a beaver!

 

Shield the alternator! here's mine, titanium sheet to reflect heat, and a high temp fabric insulation on the underside facing the alternator.

Although in reality if it does fail due to heat, it's about $30 or less in parts to rebuild. The biggest reason to shield is to not get stranded on the road!
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A picture is worth a thousand words but please forgive the poor photography. Like most of my highschool girlfriends, it's not much of a "looker" but it gets the job done! The homemade alternator survival box......
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Let's back up the technical train here for a moment. $30.00 will replace a voltage regulator and rectifier bridge. Excessive heat will melt the varnish on your stator windings and break down the insulation leading to complete unit failure. A $1040.00 touch from your friends at Ricambi.

 

True...now I don't have any experience with alternator failures (luckily), but I was thinking the heat would cook the regulator and rectifier causing a failure before more significant damage is done.

 

The proof is in the pudding. (my Grandmother always use to say this but I have no idea what it means).....
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Ceramic coatings' coefficient of expansion may be adjusted to fit the substrate.

 

Thanks, Wiley. I've heard that too. I read that the coating manufacturer can adjust the amount of crystalline ceramic component in the mixture according to the expected temperature exposure and the application material. Is this consistent with your understanding?

 

Yes, and particle size distribution too.

 

Back when I fabricated on Indycar teams and such, all exhausts were silver ceramic, made a HUGE difference underbody along with the stainless sandwich shields mounted WITH airspace. When they failed holes appeared very soon after in the carbon bodies......or the electronics died.....


But that's why I'm back here having my ploughman's lunch and a pint, cheers!

 

Otherwise know as....the Trojan effect.

 

....you're pretty good, Bob!! Although, I don't think there would be much call for an "infidel" doing stand-up comedy in the UAE.