| Author |
Message |
Tim Hogan (Tojo)
New member
Username: Tojo
Post Number: 1
Registered: 4-2002
| | Posted on Friday, April 12, 2002 - 9:21 am: | |
Hi all, I just discovered this site therfore this is my first post. What a great resource this forum is.
I just removed my headers to have them sent for ceramic coating. It is a mongrel of a job. Fortunately I've had some experiance with other 308's, Mondials and Dino's. I've found that removing the fwd set is easier if you can remove the alternator and the right fuel tank. If you cant get the fuel tank out for whatever reason, if you unmount your aircon from it's brackets, with plenty of cursing and manouvering you can get them out. This is particularly true of the Dino I have found.
As for the value of ceramic coating, the guy I help out working on Ferrari's has benn doing it for a 7 or 8 years now and says it's invaluable. Most coating firms claim that it will increase power by about 3%, reduces engine bay heating by 25%, and will protect metals from -375f to 1300f.
I reckon it's a great thing to do.
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Joel Ames (James)
New member
Username: James
Post Number: 31
Registered: 4-2001
| | Posted on Friday, March 15, 2002 - 9:26 am: | |
On ceramic coatings that are applied to the outside of the header, If you get caught in a rain storm, it is possible that if your header gets soaked, the ceramic will crack and fall off. This happened to me on my E-Type which came with ceramic coated headers. It really looks terrible when this happens. |
Anthony Tipton (Tonyt)
New member
Username: Tonyt
Post Number: 3
Registered: 5-2001
| | Posted on Friday, March 15, 2002 - 8:17 am: | |
To the issue of "powder coating" of headers to reduce heat dissipation from headers. I have just enough information here to draw some very misleading conclusions, and provide poor advice. Having covered my tail with caveats, let me generalize on some issues and questions posed in this thread.
I asssume that the "powder coating" being discussed are pure ceramic or a ceramic in a metal binder. There are many different ways to apply these coatings and each method has its advantages and disadvantages. But there are a few points which are common with all methods. First, the ceramic coatings are known as thermal barrier coatings. Ceramics have a very low thermal conductivity so if applied to the outside of an exhaust header less heat is conducted through the header and the surface temperature is lower. However, the exhaust gas stream will now be hotter due to a basic principle of thermodynamics, i.e., conservation of energy.
In short:
Be aware that if ceramic coatings are applied to outside of headers then downstream temperatures will rise. It may or may not be a problem.
The bond strength of these types of coatings generally do not exceed 10 ksi. The stresses at the header to coating interface are compressive at warm up and running but, become tensile during cool down. Do not ever induce rapid cool down on coated parts such as spraying cold water on the headers right after shutting engine off. Do not apply coating to inside of headers because the aforementioned interface will now be in tension during start-up and running and you have very little control over the heat up rate.
Thermal barrier coatings were developed to extend the thermal fatigue life of high temperature components but misapplication can and has resulted in the opposite effect. Uniformity of coating thickness is critical. If the coating is not uniform then the condition is the same as having thin to thick section changes in the base header which increases localized thermal stresses.
One secondary advantage of the ceramic coatings is that they also provide corrosion resistance.
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'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1685
Registered: 12-2000
| | Posted on Thursday, March 14, 2002 - 11:33 pm: | |
Magoo, to answer your question, I think its up to the owner of the car to take the risk in coating the headers. Either way, there's some insulation whichever is chosen (stock sheilds or coatings). If the shields are removed, coated and the headers crack, well, it'll be easier to locate the damage, remove and fix.
I've always felt that some insulation should help to reduce cracking (kinda like in welding, the post-heating of brittle alloy steels).
I've gathered the cracking instances have been due to poor construction of the headers (hot bends resulting in paper-thin metal on the outside of the bend, stresses at joints from the welding process, etc...) |
Jeff 77 GTB (Jbk)
Junior Member
Username: Jbk
Post Number: 64
Registered: 4-2001
| | Posted on Thursday, March 14, 2002 - 7:25 pm: | |
Thanks for the info Jerry. Do you have any photo's of the shielding you could post? I think I'm going to go ahead and strip off the bulky integral shielding and paint the manifolds with high temp manifold paint. This should look a lot better than the stained shielding that's there now. But I do think I'll fabricate some heat shields for the rubber parts in the near vicinity using some light gage stainless. Good luck with your removal and coating. Let us know how it turns out. |
Jerry W. (Tork1966)
Junior Member
Username: Tork1966
Post Number: 134
Registered: 7-2001
| | Posted on Thursday, March 14, 2002 - 6:24 pm: | |
Jeff, yes mine does have the heat shields in these areas. Thanks for the heads up about the possible cracking of the headers. I will keep you posted. Jerry. |
David Jones (Dave)
Junior Member
Username: Dave
Post Number: 76
Registered: 4-2001
| | Posted on Thursday, March 14, 2002 - 8:59 am: | |
Now would also be a good time to order a new gasket set for it, as well as new nuts/washers.
Never know when you will drop one and not be able to find it...
I think I got mine from T Rut. |
Richelson (Richelson)
Member
Username: Richelson
Post Number: 600
Registered: 12-2001
| | Posted on Thursday, March 14, 2002 - 8:54 am: | |
That would make sense. If not, how does it dissipate the heat more efficiently? |
magoo (Magoo)
Intermediate Member
Username: Magoo
Post Number: 2131
Registered: 2-2001
| | Posted on Thursday, March 14, 2002 - 8:49 am: | |
Also Guys, Another thought. There has been a history of these headers cracking. We came to the conclusion that it was excessive heat but could never pin it down. Does this coating hold the heat in and could it cause the headers to heat up and possibly crack? It was mentioned as a extra heavy duty coating. Just a caution. How do you guys feel about it? |
Richelson (Richelson)
Member
Username: Richelson
Post Number: 597
Registered: 12-2001
| | Posted on Thursday, March 14, 2002 - 8:47 am: | |
I didn't know you could do it with the engine in and not having to jack up the engine any. |
David Jones (Dave)
Junior Member
Username: Dave
Post Number: 75
Registered: 4-2001
| | Posted on Thursday, March 14, 2002 - 8:45 am: | |
I have done this too many times Jerry...
It seems to get easier every time.
I put the rear up on jack stands, take off the tires and wheel wells.
Take off bottom shield, release emergency brake and then remove E-brake pivot point bolt.
Unbolt header from muffler and head, have ale, beer, or something else refreshing, and wipe blood from knuckles...
This is all from memory, I may have forgotten a step or 3...
I have a set of headers I purchased from Steve M. and had them coated by HPC.
They did their Extreme hi-temp coating inside and out.
I was a little skeptical at first about the heat reduction claims.
But It has worked great, no problems running them without the stock heat shields in place. |
Jeff 77 GTB (Jbk)
Junior Member
Username: Jbk
Post Number: 63
Registered: 4-2001
| | Posted on Thursday, March 14, 2002 - 6:20 am: | |
Jerry, if you're going to powder coat the manifold, I assume the bulky integral heat shielding on the manifold has been removed, correct? Is there any other heat shielding in place to protect the nearby parts? I'm considering doing the same with my manifolds and am concerned about excess heat on the starter, the fuel hoses on the crossover pipe, and the coolant hoses. Does yours have any separate heat shielding in these areas? |
Jerry W. (Tork1966)
Junior Member
Username: Tork1966
Post Number: 133
Registered: 7-2001
| | Posted on Thursday, March 14, 2002 - 6:15 am: | |
Bret, I mean the one near the trunk...would that be the sinistra bank? |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1679
Registered: 12-2000
| | Posted on Thursday, March 14, 2002 - 12:16 am: | |
I found with my GT4 to unbolt the four main mounting bolts, unbolt the shift-shaft yoke bolt, the top engine-brace and raise the engine slightly with a floor jack and push it forward in the engine bay. This gives you enough room to slide the rear manifold out, in between the frame and the diff case.
I may have forgotten a few other items to remove/unbolt, but you'll quickly find that out...
The front manifold can come out with the engine still in, but, it helps to have the passenger's side gas tank out (for room to pull out through the wheelwell). |
BretM (Bretm)
Intermediate Member
Username: Bretm
Post Number: 1988
Registered: 2-2001
| | Posted on Wednesday, March 13, 2002 - 7:50 pm: | |
By rear do you mean sinistra or destra bank, the one near the passenger compartment or the one near the trunk? I'm rear like near the trunk. To be honest I wasn't able to get it out without moving the engine around, and I tried for quite awhile to get it. I had to pull the engine like an inch before I could work out the header. I'm not sure though, with different heat shielding it might come out in place. It seems to me this is the biggest a$$hole design possibly in the entire world. It was just barely getting hung up with the engine in place which is why I say if the shielding is a touch differnent it might come out. |
Jerry W. (Tork1966)
Junior Member
Username: Tork1966
Post Number: 132
Registered: 7-2001
| | Posted on Wednesday, March 13, 2002 - 7:06 pm: | |
Does anyone have any helpful tips, hints or suggestions on how to remove the rear header on a carbed 308? It looks to be a real task. I currently do not have any of the engine apart. My powder coat guy has offered to coat my header at no charge to try out a new extra heavy duty coating that he just got in. Thanks Jerry. |