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HEADER FUCTION

 

 

HEADER FUNCTION                                                                                   

When comparing performance exhaust systems, it's a good idea to understand the different exhaust systems on the market today and the performance demands of your engine. Understanding how a header works will help you decide which exhaust system is best suited for your application.

HEADERS HAVE TWO BASIC FUNCTIONS


FIRST IS TO SIMPLY RELIEVE BACK PRESSURE

The exhaust tube diameter is simply too small. The standard Jet boat exhaust manifold of old commonly used 2 7/8" hose to run from the manifolds to the exhaust tips. The manifolds and tips usually had about a 1/4" wall thickness so the I.D. would end up being about  2 3/8".

The standard Mercury exhaust manifold uses 4" exhaust hose but the exhaust opening is only 2 1/2". Compared to the two manifolds the LIGHTNING HEADER flows 60% more exhaust gas.  That is why we see as much as 100 HP gain in supercharged engines compared to a manifolds.

The LIGHTNING HEADERS water collector is 5" O.D.  The exhaust collector is 4" O.D.  Once the water is introduced into the exhaust flow, the water collector is then reduced from 5" to 4" for a hose connection.  With a LIGHTNING HEADER the exhaust never goes through a opening smaller than 4". 

When it comes to back pressure, any exhaust system that's less restrictive is beneficial.

THE SECOND FUNCTION IS SCAVENGING

In other words, the sucking-out of spent exhaust gases.

With high performance long duration camshafts, the exhaust valve during the overlap cycle remains open as much as 50 degrees after top dead center while the piston is starting the intake stroke.  Camshaft designs rely on the header to pull the remaining spent exhaust gas out.  The header accomplishes this by using the inertia or momentum from the previous exhaust pulse to draw out the ones behind it.  That's why a long tube header works better than short tube header.  They isolate the pulse to maintain a high velocity and create a low pressure behind it.  To test this principle take a header and blow compressed air into any port.  Take a piece of paper and place it over any of the three remaining ports and note the suction that is created by the discharging air.  This is where LIGHTNING HEADERS out perform most other exhaust systems.  With long primary tubes, they have a strong scavenging effect.  Long duration camshafts need a scavenging style exhaust to work to their full potential.

HEADER PERFORMANCE

Performance figures on headers vary considerably.  As a rule, the higher horsepower engines benefit more than the lower horsepower engines.  For example, a 330 HP Big Block Chevy Mercury engine will gain approximately 75 to 100 RPM (20 HP), where as a 365 HP Big Block Chevy Mercury engine will gain approximately 300 to 400 RPM (50 HP).  Supercharged Big Block Chevy Mercury engines gain up to 800 RPM (80 to 100 HP).  

For real performance figures click here.

 

 

HEADER CONSTRUCTION

LIGHTNING FRESH WATER HEADER CONSTRUCTION

Our fresh water header starts with mandrel bent 304L stainless steel interior tubes.  The standard tube headers use 2" OD primary tubes.  Our big tube headers use 2 1/4" OD primary tubes.  The exterior tubes are mandrel bent heavy wall steel tubing.  The standard headers use 2 1/2" tube.  The big tube headers use 2 3/4" tube.  By using large diameter exterior tube, this leaves a generous water jacket area that runs the entire length of the tube.  This is essential for a long service life.  The exterior tubes are mechanically etched prior to assembly.  During assembly, the complete header is TIG welded and a custom alloy welding rod is used in all critical areas.  Finally, a corrosion resistant silicone ceramic coating is applied to the interior of the header while the exterior receives a black powder coat finish.  Colors are optional.  Headers come complete with aluminum water distribution tubes, gaskets, hose, clamps, bolts etc.

 

LIGHTNING SALT WATER HEADER CONSTRUCTION

Our salt water header starts with mandrel bent 316L stainless steel interior tubes.  The standard tube headers use 2" OD primary tubes.  Our big tube headers use 2 1/4" OD primary tubes.  The exterior tubes are mandrel bent 316L stainless steel tubing.  The standard headers use 2 1/2" tube.  The big tube headers use 2 3/4" tube.  By using large diameter exterior tube, this leaves a generous water jacket area that runs the entire length of the tube.  This is essential for a long service life.  During assembly, the complete header is TIG welded and a custom alloy welding rod is used in all critical areas.  Next, the water distribution tube is welded to the bottom of the header.  After assembly, the entire header is stress relieved, annealed, and heat treated to maximize its corrosion resistance.  A black powder coat finish is standard; colors and polishing optional. 

 

HEADER WARRANTY

LIGHTNING ONE YEAR LIMITED WARRANTY

LIGHTNING PERFORMANCE MARINE warrants its products to be free from defects in materials and workmanship as follows:  Products found to be defective within 12 months from the date of purchase will be replaced or repaired free of charge.  LIGHTNING PERFORMANCE MARINE makes no warranty as to merchant ability to fitness of it's products for a particular purpose.  Repairs or replacement will be at the discretion of LIGHTNING PERFORMANCE MARINE and must be returned to us freight prepaid.

 

WARRANTY SHALL NOT APPLY TO:

Any product that has been modified or improperly installed.  This includes repowdercoating headers, adding EGT or O-2 bungs.

Any product failure due to a lack of maintenance.

Any product that has been used in racing and is operated in excess of its rated limit.

LIGHTNING PERFORMANCE MARINE responsibility in respect to warranty claims is limited solely to repair or replacement of product found by LIGHTNING PERFORMANCE MARINE to be defective.  LIGHTNING PERFORMANCE MARINE does not pay for labor charges connected with removal of installation of repaired or replacement products or for any other incidental or consequential damages.