Exhaust Header Tube Sizing and Length
- The size of the primary tube must meet the requirements of the engine and the vehicle’s intended use.
- The length of the header tubes and collector size meets the RPM requirements and the use of the vehicle.
- The headers actually fit the vehicle without having to use a sawzall, cutting torch, or sledge hammer to persuade them into place.
Header Primary Tube Size
Primary Tube Length
- Lighter weight
- Gear reduction design provides increased torque and faster cranking speeds
- Lower power drain
- Easier on flywheels and flexplates
- Infinitely adjustable clocking (many brands have this feature)
- Reduced negative affects from header/exhaust heat
- Smaller overall dimensions
For many classic vehicles using OE-style rebuilt starters purchased through common parts stores, it is difficult to ensure that the starter core provided by the store’s electrical rebuilder is one that originally came on that specific vehicle. Rebuilders often combine numerous OE part numbers into one general (fits all these applications) part number. The starters may be of varying dimensions (length, width, diameter) or clocking, but somehow now use the same part number from the rebuilder. These combined numbers may fit a variety of vehicles using factory exhaust manifolds without any interference issues. However, that same starter may not work on the same vehicle once headers are installed. This is because header manufactures will design a header using a project vehicle that uses the correct original starter part number for that vehicle model/year. If the starter on that vehicle is not original or compatible with what the header manufacturer had on the project vehicle, a different, compatible starter is required. This is easily alleviated by upgrading to a mini-starter and the benefits it provides.
When choosing a mini-starter, compare manufacturer warranties and features (like unlimited clocking of the housing). Those with the best warranties often use the best armatures and other components.
In a final note, all modern vehicles come from the factory with smaller, more efficient gear-reduction starters. Why install a bulky, heavy, inefficient OE-style starter on an engine or vehicle that has already incurred thousands of dollars in meticulous improvements? Doing so could be compared to wanting solid rubber tires and wooden wheels on an otherwise fully modified classic street rod! Get the better mini-starter and know you’ve made a responsible decision!
But My Engine Builder (or Crate Engine Spec Sheet) Told Me I Need ____Size Header…
The ZZ383 High Performance engine should be installed with a pair of high performance headers for maximum performance. 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.”
It is possible that someone reading this article is unfamiliar with the term step-header. This is because step-headers are used primarily in race-only applications. However, more and more header manufacturers and engine builders are seeing the potential this technology offers. A step-header design is that which has more than one size of primary tubing, sectioned in simple 1/8″ increases over the length of each tube. The header begins at the cylinder head with a smaller tube diameter and then increases in usually one or two larger incremental sizes that occur at calculated distances from the cylinder head flange. Where the steps (increases in tube diameter) occur depends upon the engine size, operating RPM, exhaust timing, engine bore and stroke, and numerous other factors. New technology and research has also evolved into the development of stepped design shorty headers.
Optimized for 499.665 CID engine at 9000 RPM
Length = 21.2 to 24.4 inches long
1st Dia. = 2.227, Length = 10.6 to 12.2
2nd Dia. = 2.352, Length = 10.6 to 12.2
1st Dia. = 2.227 Length = 10.6 to 12.2
2nd Dia. = 2.352 Length = 5.3 to 6.1
3rd Dia. = 2.477 Length = 5.3 to 6.1
Diameter = 4.028 to 4.278
Tuned Lengths = 12.3 best (and also 6.1 or 24.5)
Diameter = 3.528 taper to 4.528
Megaphone/Diffuser Length = 12.3 inches
Total Exhaust System Tuned Lengths (Primary ends to TailPipe end)
Best HP/TQ Tuned Lengths = 12.3 , 24.5 , 49.1 , 98.1 inches long
Note -> all Pipe Diameters are OD and based-off .0625 inch Pipe thickness
Those who originally bad-mouthed step-header technology also condemned the software used to find these dimensions. PIPEMAX is only one program of many, and most engine builders and race teams use a variety of software simulations as a guide or baseline when testing and developing engine components and combinations. These programs are extremely detailed and intricate tools designed to help the industry professional. Oddly, many of the original detractors have since embraced step header technology.