Originally Posted by itzjere

What do you mean by wrapping the header?

Originally Posted by Racing Superstore

Think of exhaust gases as a piston moving down through the tubular system. As each pulse travels down the system, it creates a vacuum behind itself. The negative pressure behind each, is the scavenging effect. As the velocity of the pulses increase, the negative pressures also increase. As you have an increase in velocity, the length of time that you have a negative pressure in the system is increased. The net result of higher velocity to assist in scavenging is increased performance of the intake and exhaust system. Maintaining higher exhaust temperatures throughout the system increases performance in many ways.

Think of exhaust gases as a heavy liquid such as an oil additive. If the liquid were traveling down a tubular system in a cold state, it would move very slowly. If you were to heat the liquid, the density of the fluid changes. The liquid responds to the heat increasing Its velocity. Exhaust gases respond In the same manner. Higher temperatures in a system increases the flow of the system. If the liquid is allowed to cool in the system, It slows down the flow of the liquid. By this Illustration, you can now see the importance of maintaining higher temperatures in a exhaust system.

The Incoming air charge increases due to many different factors. First, the lowering of air induction temperatures and cooler fuel coming into the engine will increase horse power by over 1% per Degree drop In temperature. Other areas of performance are Improved by the increased scavenging effect. Increasing the scavenging effect of the exhaust allows the engine to breathe more efficiently. A engine in many ways is like an air compressor, the pushing of exhaust gases from the combustion chamber creates a condition called pumping losses. This is the loss of power due to the piston pushing these exhaust gases Into the system and out of the system. Increased scavenging not only lowers pumping losses but also allows more efficient clearing of exhaust gases from the combustion chamber. This means cleaner air fuel mixture, this means power. The increased scavenging effect of the exhaust also benefits the intake of air & fuel during the overlap phase of the intake stroke. During the overlap phase, both the intake & exhaust valve are open. The exhaust gases create a vacuum effect which pulls the air fuel mixture at a higher velocity through the intake. As you can see, there are many benefits to the use of our product, lower cockpit temperatures, lower under hood temperatures. These all mean increased life of
electric & electronic components.

Originally Posted by Century Performance Center

Many times I've been asked about, or have commented on the use of header wraps. This issue is a real pet peeve of mine. Good or bad about a product I'll give my opinion based upon direct use and fact.

THE FACTS:

Header wraps are designed to keep the heat in the header to improve scavenging of the cylinders. Keeping the heat in the header allows the exhaust speed to remain high. (the right idea)
There are no header manufacturers that I know of that will warranty their headers if any header wraps are installed on their products.
In most cases the header wrap damages the headers beyond repair. (I will explain below)
If you run a lean mixture, you "may" see a slim performance gain using header wraps. A rich mixture may show slim to absolutely NO gain in performance.
If you do not mind replacing your headers and header gaskets regularly, and you like that ugly look of a wrapped header, go ahead and use the heat wrap.
BACKGROUND INFORMATION:

In the past, almost all NASCAR and other racing engine builders used the header wraps for the added power gains. But, after having to replace the headers after each race due to the wrap being about the only thing holding the header together, they do not promote the practice any longer! They now utilize the thermal coatings that are chemically and electrically applied to the headers. Those include Airborn, Jet Hot, HPC, and others.

Imagine having to replace a $1200.00 plus set of headers after each race weekend! Few but the most financially well-off race teams can afford to do this. But, it is also in the downtime for remaking a custom set of headers. Most custom header makers do not have copies readily available.

I believe that the wraps are good to protect various items from heat, but not to hold the heat in the header. For example: you can use the wrapping for the protection of fuel and oil lines, wiring, etc.

Cool air needs to be around the header, and insulating it with a wrap to hold exhaust heat in makes the header material temperatures near molten. When you wrap the header you trap the heat in the header, but also in the material that needs to breathe to dissipate heat for it's own survival.

Engineers, Metallurgists, and other experts out there will state that there is no way that the material can fail because it can withstand, and it was designed to withstand, the internal temperatures of exhaust gases. TRUE! But, when the header is not allowed to cool so as to dissipate those extreme temperatures that the wrap is controlling, you have now developed a heat absorption that compares to thermal friction which will will continue to gain in temperature beyond the normal exhaust gas temperatures (EGT's). This is the same as with most any insulation.

Try this experiment ... launder a load of bath towels and then dry them. Immediately pull them out of the dryer and just toss them in a snug pile on your bed. Now leave them there for a day and then open them. You will find that there is still a considerable amount of heat left in the center towels. This heat, even though the outer towels and bed are normal room temperature have been able to contain their heat. This is a simple thermal insulation test, but with your headers you have an internal heat supply coming from the engine. The heat on the outside portion of the header material is trapped between the warp and the header and will continue to fatigue the header. This build of heat is amplified by the wrap. Towels do not need to breathe, header material does.

The EGTs stay the same but the properties of the header material changes in a way of amplifying the temperatures because of the insulation. This action goes against normal laws of thermal dynamics, but this effect is fact, and you have to pull the ears off most engineers before they believe you. This is the trouble with plenty of education, but NO "common sense"!

Originally Posted by hotbox05

u can re-use the donut. but you will need new bolts. u can reuse the nuts an bolts that attach the header to the head but must use new onse for the a pipe to b pipe aka the downpipe or stock exhaust section

Originally Posted by itzjere

I think I'll be going with Megan Racing Header. Does anyone know if I can use the existing bolts off my stock header to install the new Megan Racing one? I plan on using the existing donut gasket.

Originally Posted by mgithens

you're never supposed to reuse engine bolts... they are intentionally installed in such a way that they slightly stretch upon the first installation , this causes the material to have a better hold... you cannot ever have the same tension in the bolts once you take them out, this is due to plastic deformation...

I'm not saying it isn't possible to reuse them... I am just saying that you are asking for trouble... seriously, consider dropping the cash to replace to avoid problems.