How do you choose exhaust headers?
- Understand how exhaust headers work
- Determine the diameter size of the primaries
- Consider the length of the headers
- Check the material of the header
- Don’t forget the collector
Full Answer
How do you calculate the height of a header?
It went like this: Measure the span in feet and add 2 to that number. The sum will be the height of your double header in inches. For example, if the span is 4 feet, add 2 to 4 for a sum of 6. Therefore, the header would need to be made from doubled 2x6s. For odd numbers, round up.
How do I estimate my exhaust tube size?
Editor’s Note: The easy to read tube size charts replace our original exhaust diameter calculator for ease of use. Easy Way To Estimate: Your intake system needs to flow 1.5 CFM per engine horsepower, and your exhaust system needs to flow 2.2 CFM per engine horsepower. Good Way To Estimate: Take engine RPM x engine displacement, then divide by two.
What size header do I need for my engine?
Example: On a common small block V8 engine producing 300-400 horsepower and installed in a street rod that is going to spend most of its time operating stop light to stop light, a 1-1/2" primary tube header is perfectly effective. Add a supercharger to the same engine and a 1-5/8" to 1-3/4" header is better suited.
How does header size affect engine performance?
Too large a header will reduce torque output of the engine and increase the possibility of exhaust gas reversion---again increasing heat. Simply put, torque is related to air velocity (the faster the air/fuel get through the engine), and horsepower to the volume of air/fuel that processes through the engine.
What is the difference between a header and a tube?
How much torque does a 425 horsepower engine have?
How to control exhaust velocity?
What is the collector size?
Why do headers need a mini starter?
How to build a step header?
What size headers are used on a ZZ383?
See 2 more
How do you choose a header size?
To decide on the right primary tube diameter, there are numerous formulas used in the design of race headers, but for a street car, Don Lindfors of PerTronix (makers of Doug's, Patriot, and JBA headers) says the following is a great rule of thumb: 200-325 hp look for 1.50-inch diameter primaries, 275-425 hp use 1.625 ...
How do you know if headers will fit?
Exhaust Headers are designed to fit a specific combination of engine and vehicle. Just because a set of headers fit a similar vehicle with the same engine, doesn't mean it will fit your car. The Header Flange must match the cylinder head bolt pattern. It also must accomodate the exhaust port size, shape, and location.
How do you measure header pipe size?
First, find the circumference of the pipe using a tailor's measuring tape (or a piece of string you can then measure with a standard measuring tape or ruler). Then, divide the circumference by p (3.14) to get the outside diameter.
What headers are better short or long?
Short tube headers are better when it comes to fuel efficiency. It has to do with its length, having shorter exhaust flow allows the engine to deliver power more efficiently. It works best at lower RPM range, where most of us will be driving the most. The long tube headers require more air to be sucked into the engine.
What headers give the most horsepower?
Shorty headers deliver better low-to-mid-range torque. Medium and long-tube headers allow an engine to make more horsepower at high rpm.
Is exhaust pipe measured inside or outside?
Most exhaust piping is going to be measured using OD dimensions which is outer dimensions of the pipe or the outer diameter. That means if you were to purchase a three-inch pipe—let's say like the one we have here—the outside diameter of this pipe would actually be three inches.
How do I know what exhaust tip to buy?
The inlet size of your exhaust tip must match the diameter of your existing tailpipe for a proper fit. All of our exhaust tips specify the inlet sizes available for each model, so keep your size in mind when ordering. For example, if your tailpipe has a 3″ diameter, choose an inlet diameter of 3″.
Does pipe size affect exhaust sound?
If you are too lazy for the details, bigger exhaust pipes do make the exhaust louder – but only by a little. Exhaust pipes are made bigger to allow better exhaust flow. This is important for increased performance and horsepower (not for the sound).
How do you fit exhaust headers?
6:3612:27How to Install Headers - YouTubeYouTubeStart of suggested clipEnd of suggested clipReading. All right now grab your headers. And then go underneath the car now you're going to want toMoreReading. All right now grab your headers. And then go underneath the car now you're going to want to Jimmy your exhaust system now up to the engine.
How long should header tubes be?
Most racing engines will work best with (primary) tubes between 28 and 30 inches long. It is also very important that all header tubes are as close as possible to the same length.
How long should header collectors be?
Many small block racing engines perform better with collector diameters between 3 and 3-1/2-inches,” Reher said. “Large displacement, high-horsepower engines require 4-5-inch (diameter) collectors. The length for most drag racing applications varies between 8-inches and 14-inches.”
What are Tri Y headers?
Invented by Doug Thorley Headers, the Tri-Y header is designed to match the synchronization of the engine firing order, thereby maximizing exhaust scavenging. This design creates the optimum torque and greatest horsepower gains in comparison to any other design.
How many CFM does an exhaust system need?
Easy Way To Estimate: Your intake system needs to flow 1.5 CFM per engine horsepower, and your exhaust system needs to flow 2.2 CFM per engine horsepower.
How many CFM per square inch of exhaust pipe?
Exhaust Pipe Size Estimate: A good section of straight pipe will flow about 115 CFM per square inch of area. Here’s a quick table that shows how many CFM each common pipe size will flow, as well as the estimated max horsepower for each pipe size:
What gauge is a pipe?
NOTE: These numbers are just estimates. All pipes are assumed to be 16 gauge steel.
How to measure double header?
It went like this: Measure the span in feet and add 2 to that number. The sum will be the height of your double header in inches.
What is a header in a building?
Simply put, a header (in this case) is a horizontal member that spans a wall opening such as a door or window to transfer loads from above down and around that opening. There are too many “load” variables to consider in one simple formula or rule. Snow loads can vary tremendously, as can roof, ceiling, and floor loads and the various combinations and permutations of those loads—all of which can vary depending on the width of the building.
How many 2x6s for a 4 foot span?
For example, if the span is 4 feet, add 2 to 4 for a sum of 6. Therefore, the header would need to be made from doubled 2x6s. For odd numbers, round up.
Is there a rule of thumb for headers?
So the short answer is, there is no comprehensive “rule of thumb” that is useful (and safe) for designing headers.
Who is Darren Tracy?
A: Darren Tracy, P.E., owner of West Branch Engineering, in Saratoga Springs, N.Y., responds: Before becoming a licensed professional engineer, I was a contractor. When I had just started my business, I did any kind of job I could find in order to make a living, often working on small remodeling jobs or additions.
How do exhaust fumes flow?
Exhaust fumes flow in one direction — from your engine back to the tailpipe. Som e exhaust systems use different diameter tubing at different points along the path. For example, the tubing between the exhaust manifold and muffler might start at 2.5”, but then it might switch to 3” for the tailpipe. When you’re taking your measurements, make sure to check both the inlet sizes (the section pointing towards your engine) and outlet sizes (the section pointing towards your tailpipe).
Why do exhaust tips use internal diameter?
So, just the space inside. Gener ally, exhaust tips and mufflers use an internal diameter measurement because they usually slip over the exhaust pipe. Most exhaust piping uses an e xternal diameter measurement.
What to do if a pipe is blocked?
If the end of the pipe is blocked, use a pair of dial calipers to measure the distance. If the end of the pipe is blocked and you don’t have a pair of dial calipers handy, you can use a bit of arithmetic instead.
How to measure the outside diameter of a pipe?
How to Measure Outside Diameter. If the end of the pipe is fully exposed (not covered by an exhaust tip or fitted into a muffler), use a tape measure or ruler to measure. Remember, you’ll be measuring from one outside edge to the opposite outside edge, across the center point.
What is the external diameter of a tubing?
The external diameter is the distance from edge-to-edge, including the thickness of the tube itself.
How to measure the distance from the inside edge of a pipe?
If the end of the pipe is exposed, use a tape measure or ruler to measure the distance from the inside edge to the opposite inside edge through the center point. For a more precise measurement, use a pair of dial calipers.
Can you use a band clamp on exhaust pipe?
You can use a band clamp or U-bolt to secure the connection or you can weld the joint for a leak-free fit. Many exhaust tips have band clamps built right in, but you can always weld for extra security. When two sections of pipe are the same outside diameter, they create a butt joint.
What is the difference between a header and a tube?
Smaller primary tube diameters keep the air velocity up for more torque, where a larger tube size is better for upper RPM (above 6,500 RPM) performance. If the headers are too small for the application they will cause restriction and increase heat in the engine. Too large a header will reduce torque output of the engine and increase the possibility of exhaust gas reversion---again increasing heat. Simply put, torque is related to air velocity (the faster the air/fuel get through the engine), and horsepower to the volume of air/fuel that processes through the engine. The faster the air enters and exists an engine the more torque the engine makes, and the more volume of air that passes through the engine, the more horsepower the engine will produce. A balance of both is necessary for typical street applications, where racing-specific engines are often designed within specific RPM range requirements.
How much torque does a 425 horsepower engine have?
Having 425 peak horsepower and 449 ft/lbs of torque under the hood is decent, but really, anything over 5,000 RPM in this example merely amplifies wear and tear on the engine. Torque is falling, and peak horsepower occurs just 400 RPM higher (900 RPM over peak torque). The big torque numbers occur between 3,000 and 4,500 RPM. Therefore, even if driving this engine hard (or racing it), we'd want the shift points to allow the engine to fall to roughly 3900-4,200 RPM for maximum continued acceleration (pull).
How to control exhaust velocity?
In simple terms, by starting with a slightly smaller tube, the exhaust velocity stays up. As the gases expand, it hits the next size step. This allows for contained control of the expansion while still keeping velocity speed high. This would also continue to the third step, and then to the collector. This gradual increase in size provides the maximum balance of exhaust velocity and volume. In more complex terms, we look at the pressure waves within the header primary tubes. Engine pulses in an equal-length, tuned header create what is called rarefaction, or a negative, low-pressure wave that is partially compressed and redirected back up the primary tube toward the exhaust port. This wave reaches the exhaust valve about the time valve overlap occurs (when both intake and exhaust valves are open). It is easy to believe that these rarefactions are bad, or something we don't want. However, on an internal combustion engine we actually want to control them to our benefit. The animated image below (source: Wikipedia) shows a sound rarefaction. The official definition states, "a reduction or diminution of an item's density, opposite of compression, especially in air or a gas."
What is the collector size?
Collector size is measured in both length and diameter . In a shorty, street rod type application the collector length is of no concern. In these headers the collector is merely a union point for the primary tubes, and a connection point for the vehicle's under chassis exhaust system. The collector diameter is important in that the application requires a diameter compatible with both the power output of the engine, and the under chassis exhaust piping size that completes the rest of the vehicle's exhaust system. Of course, most headers come with a collector reducer to meet the size of a smaller exhaust system, but with a shorty or mid-length header the collector is already manufactured using a standard sized complimentary collector for that header and the engine it fits. On these applications it is common (and cleaner) to have a one-piece down pipe fabricated instead of using the reducer. If someone does not have access to a muffler shop, tubing bender, or other fabrication equipment, the reducer provides a weld point for under chassis exhaust piping connection.With a full length header the collector diameter is usually fairly large in all but those designed for light duty passenger cars, trucks, SUVs and motorhomes. This is due to the fact that most full length header designs are for max power, and upper RPM use. Additionally, in racing applications we often use the collector length to slightly tune the torque output of the engine.
Why do headers need a mini starter?
Many headers require the use of a mini-starter to ensure adequate header to starter clearance. However, upgrading to a mini-starter is actually beneficial for many more reasons.
How to build a step header?
A step-header is built by starting with a slightly smaller tube, then going up in size in one more (2-step), or two more (3-step) sizes. Examining the exhaust port of most cylinder heads, it is easy to notice that they are typically NOT the same size as the header tubes. Header flanges are rarely the same size as the tube diameter, and often not a direct match in dimension to the exhaust port itself unless it is a race-only application that the user/builder modified---or again, someone looking to spend the time and expense to find every last available 1/4-horsepower. If the exhaust ports on the cylinder heads get too big, air velocity and torque suffers, and this also increases the possibility of reversion. As the exiting exhaust gases travel through the header tubes, expansion occurs until cool enough where expansion slows, reducing air speed and scavenging effects. The longer the exhaust velocity remains at or near its highest values, the better the scavenging of the cylinders, and the more power and torque the engine can provide.
What size headers are used on a ZZ383?
The headers used during development of the ZZ383 had 1.75" diameter primary tubes. Primary tubes were approximately 32.00" in length and had 3.00" diameter collectors. Using a similar combination in your application, along with a performance exhaust system with a balance tube (“H” pipe) and low restriction mufflers, will provide you with optimum performance from your ZZ383."
