Coating = Snake oil One major benefit of headers is to wick heat away from the engine, unlike cast manifolds. This stuff just keeps the heat in the engine and exhaust pipes. If you read carefully, the only selling points they have in that article are things like: Race teams use it... Big deal! Reduces heat so your engine paint lasts longer... Again, big deal! Keeps underhood temps lower... Why is that a benefit??? You can touch the exhaust pipes with the engine running... Why??? It also claims that your engine oil and tranny fluid last longer with coated headers. Sorry, but I have to disagree here... Your headers will only heat your engine so much from radiant heat, and it is surely less than keeping the heat in the headers (and therefore head) and letting the entire long block heat soak. The reason your car gets hot under the hood is because it is dissapating heat. That is a GOOD thing! When headers wick heat away from the heads: You can run lower octane fuel. You can run higher compression. You can run more timing. Pick your poison. Your engine also runs cooler and doesn't work the radiator as hard. With more heat in the exhaust, the gas velocity in the pipes is faster, which in theory adds torque, but only if your pipes are TOO BIG to begin with. Think about this: Exhaust gasses SHRINK as they cool, which in turn means you get better flow out of a smaller (and lighter) exhaust pipe as the system progresses back. If you keep the heat in the pipes, you are pushing expanded gas through pipes and causing restriction at the muffler (race cars don't use mufflers), and if you have average exhaust pipe diameter, you limit your flow at higher rpm in order to gain a minute bit of torque. If you feel you need the extra bit of torque, why not use a smaller pipe in front of the muffler? That way you gain from throttle response and lost weight... It's supposed to be hot under the hood. Headers are supposed to dissipate heat. Headers, being steel, last longer when they can dissipate heat. Dave
I just had my headers Jet Hot coated but I was looking for something pretty My other two cars have stainless steel header paint from eastwood.
It makes a difference if you don't have cold air induction and have to get the intake air from under the hood. My Jet-Hot coated headers dropped the tube temperature from 500* to about 300*. It's easier on the plug wires and nice when you don't have to wait for a 1/2 hour cool-down to pull your plugs. Oh yeah, like Thomas said, they look nice, too.
I don't want to sound like an azz, I am not trying to be smart... It is common sense. Exhaust gas shrinks as it travels away from the engine and cools. Simple physics. If you want a source, probably CC or Hot Rod mag. Don't remember exactly where I picked that up. If the gasses cool, you can flow same-same through smaller pipe. This is one reason you try to get your mufflers to the back of the car. Right on the headers and they wear out quicker from the heat and flow less effieciently from the heat. The headers wicking heat and the engine running cooler with them has been common knowledge for decades. When the headers wick heat from the exhaust, it causes a chain reaction that allows the entire engine to run cooler. An engine that runs cooler can resist detonation, therefore compression/timing/octane can be varied easier. This is the same thing with aluminum heads. They cool faster than cast iron, like headers vs iron manifolds, and cause the same chain reaction in cooling. This is why aluminum heads also allow an increase in compression. So, uncoated headers: Wick heat from entire engine Take dangerous heat from the combustion chamber Cause cooler, therefore more compact, exhaust gasses to flow better through pipes/mufflers. Coated headers are then obviously detrimental to the above effects, and common sense tells me that the hotter, therefore bulkier, gasses would cause the need for larger pipe. Otherwise flow would be impeded as the rpms rose. Also, like I hinted at earlier, mufflers last longer when kept cooler. This is especially true for mufflers with a fiber filler of any type. Hotter exhaust shortens muffler life. So, are any of these things not sensible? You ask my source of info as if there is mystery here. As far as plug wires, that's easy! Get kevlar heat skirts for the plug end. Dave
The main reason I got my headers coated was because they were turning into piles of rust. Having them coated inside and out put a stop to that. As mentioned, it helps cool the intake charge and floorboards, and no, I don't want to hang Kevlar bootys on my plug wires. Guess I'd have to see proof that you would get more power from "wicking" (actually it's called heatsinking) heat through the uncoated headers than the scavaging effect from increased exhaust velocity in coated headers. Generally for a heatsink to work you need a large surface area (surface color and texture are important) and/or a large mass of thermally conductive material. Headers have a lot of surface area but not much thermal mass. It would be an interesting test. Personally I rather have the heat going out the rear of the car than hanging around in the engine compartment. The heat there can affect more than just plug wires. Any wiring, solenoid, battery, hoses, etc., don't like heat. And did I mention the coated headers look much better?
You are absolutely right about the headers looking better. Paint is a serious pain to do correctly and get it to keep. When done right, or kept up with every couple years, they last for me just fine. My ol' man's car has had the same headers since 78... We painted them every 10-12 years, and did it right. The car has been parked about 8 years, but the headers are still solid from paint about 15 years ago. You did good having the headers coated in and out. Most header companies coat only the outside, so the headers rot from inside. And they rot faster from what I hear because the outside coating keeps the heat in the pipes which in turn rots them faster. That is why header makers void the warranty if you wrap your tubes. The wrap heats the mild steel pipe to brittle and ruins them. Jet Hot is the only company that I know of personally that coats inside and out. Heat sink is probably a good term, although like you say, headers don't quite fit that term. However, compared to cast iron manifolds, they are a much more effective heat sink. Other than increased flow, that is the second best reason they are so popular. Anyway, IMO, headers 'heat sinking' into the engine bay does not adversely affect anything other than non-silicone plug wires and maybe a starter that is borderline anyway. Both are easily overcome. Tip: Black silicone is FAR more heat resistant than a colored silicone boot. By hundreds of degrees... To color the boot, they use dyes in the silicone that reduce the heat resistance. Source: CC magazine. My opinion... Snake oil. One man's snake oil may be another's treasure!
