Engine Tech: Header Types and Applications

SHORTY HEADER:
This type replaces the stock exhaust manifolds in some production automobiles. Usually “Smog Legal”. Two types are available a shorty and equal length, the equal length type has a little better mid-range torque and is the same in power at peak RPMs. The unequal type usually runs as hard as the former and is easier to work with plug access at the racetrack. We have tested this and the difference is not even measurable even on blower applications. Dyno difference does not show at the track, this is because the “Peak” Hp was the same even with the superior mid range torque of the equal length.

FULL LENGTH 4-2-1:
This header type is basically used for mild applications for street use. Regarded as inferior to a 4-1 type. It is however underestimated in its potential, its superior mid-range benefits milder engines and is usually found in impressive road race efforts. I have seen this type of headers out perform the conventional 4-1 type at the race tracks, this is evident that this combination really responds well on anything short of an all out racing engine.

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4-1 HEADERS:
This was the standard norm in header design until the advent of the “Step Header”.
Usually of the equal length design, this misleads racers under the mistaken notion of “Equal Length means Equal Flow”. In the pursuit of equal length several additional bends are applied to the primary pipes that defeats this purpose of equal flow!
The good designs has to have close to Equal Flow at every primary pipe regardless of the variance in length. Care has to be taken to make sure to minimize the bends to a minimum number.
This header design is used by the majority of Competition Engines. When sized correctly in the primary pipe diameter as well as applying the same with the secondary pipes or collector, the engine builder/tuner can affect his powerband or RPM range.
Extending the length of the secondary pipe or collector will affect the performance of the engine, Lengthening this usually gives more low-end and mid-range torque.. Also increasing the diameter of the collector will affect top-end power.
On a Short Track or Road Course, The Primary pipe is Smaller and shorter to build torque on the lower to mid RPMs. Collector size is also on the smaller end of the scale.
On an all out Horsepower Track or Drag Strips, the primary length is longer and the diameter is bigger for top-end flow. Collector size is much bigger, on average at least half an inch or an inch bigger or more in diameter is normal to see.

STEP HEADER 4-1: MERGE COLLECTOR
This is the latest type being used by the Leaders of the Pack!
The Engine Builder employs this type to take advantage of the velocity of the exhaust gases exiting the port with a smaller primary pipe. As the gases looses heat while flowing downstream it looses velocity and becomes slower and heavier to move, consequently a larger diameter is employed to decrease the ever increasing back-pressure and slowing gases. Another increase in diameter to compensate and decrease the back-pressure build up is employed. The purpose is to keep the flow moving with an increase in diameter and the effect of this ability to move more gases by its larger size.
A total of 2-3 pipe diameter increases are employed.
My Engine required 2″ coming out of the heads at about 6″ in length, this is followed by 2.1/8 and steps up to 2.1/4 going to the collector. There is definitely a power difference noticeable at the Race Track.
I dont think you can compete Competitively with a standard 4-1 lay-out on your exhaust headers against the STEP 4-1s!
This lay-out in combination of a “MERGE” collector SPELLED THE END OF THE 4-1 headers.
The MERGE COLLECTORS picks up the velocity where the pipes converge to increase exhaust flow! This helps velocity again as the ever increasing diameter of the Step design looses velocity as it travels downstream of the primary pipe.

180 DEGREE HEADERS:
To be continued-where’s my taho??
Updated:
This is the exotic type used in Indy, F-1, and Pantera, and GT-40 kind of cars. Basically pairs Cylinders firing 180 degrees from apart to maximize scavenging of the cylinders. Pairs crossing over the other bank and basically making the engine sounds like its got a Flat Type Crankshaft! Sounds like a Ferrari as this employs a Flat type crankshaft. This is as far as I want with this as it does not apply to the average guy….

HEADER TIPS:

1. Construct your header tubes to arrange the primary pipes to FIRE ROTATIONALLY! Adds to the scavenging of the engine when, the exhaust gases exiting one tube passing the opening of the tube directly next to it. This creates a “Suction Effect” on that tube than the one opposite to it inside the collector. This results in a ROTATIONAL FIRING PATTERN!
2. Use a Mandrel Bend instead of a pipe bend to limit flow losses.
3. Coat the headers or Thermal Wrap as keeping the gases from cooling rapidly, this will help them propel themselves out to Atmospheric Pressure.
4. If not Thermal wrap or coated, Stainless Steel Headers are also very efficient Heat Retainers and will perform just as good if not better.

TIPS TO THINK ABOUT:
PAY ATTENTION TO THE EXIT ANGLE OF THE HEADER PIPES IMMEDIATELY AFTER THE FLANGE PLATE.
AN ABRUPT DOWNWARD CHANGE HERE WILL AFFECT POWER. IF THE PORT ANGLE IS UPWARDS DO SO AND CARRY THIS 4-7 INCHES OR MORE BEFORE YOU START TURNING AND BENDING DOWN. DO THE SAME AND KEEP IT STRAIGHT AS FAR AS POSSIBLE ON ALL APPLICATIONS.

VARYING YOUR PRIMARY PIPE LENGTH WILL AFFECT YOUR HORSEPOWER, ALSO CHANGING THE LENGTH OF THE COLLECTOR WILL AFFECT YOUR TORQUE OUTPUT ON THE RPM RANGE.

A SIMPLE CAN OF PAINT APPLIED TO YOUR HEADERS CAN TELL YOU WHEN AND HOW LONG A COLLECTOR NEEDS TO BE!!!

INSTALL A MANOMETER AND SEARCH THE UNDER PAN OF YOUR VEHICLE TO SEARCH FOR A “LOW PRESSURE AREA ” TO DUMP YOUR MUFFLER EXIT OR COLLECTOR EXTENSION!!! THIS HAS A SUPERCHARGING EFFECT IF THE ENGINE DOES NOT HAVE TO FIGHT THE PRESENCE OF ATMOSPHERIC PRESSURE CREATING A BACK PRESSURE TRYING TO INHIBIT THE EXHAUST FROM EXITING!

A SMALL 3/16 HOLE DRILLED STRATEGICALLY AT THE HEADER PIPES WILL POSSIBLY MAKE MORE POWER BY MAKING THE HEADERS PERFORM BETTER BY THERMAL RE-HEATING!

IF BUDGET PERMITS IT, COAT OR WRAP THE WHOLE SYSTEM ALL THE WAY TO THE MUFFLERS. RETAINING HEAT IS THE NAME OF THE GAME.

PLACE A “REVERSION LIP” ON THE TOP PART OF THE HEADER, TO INHIBIT THE REVERSION OR FLOW-BACK OF EXHAUST GASES BACK TO THE CYLINDERS.

AT A MINIMUM INSTALL YOUR HEADERS SLIGHTLY HIGHER THAN THE PORT “ROOF” OF THE EXHAUST PORT. THIS MISMATCH AT THE TOP OF THE PORT IS A POOR MAN’S REVERSION PREVENSION….

TURBO APPLICATION:KEEP YOUR HEADERS SHORT, THE CLOSER TO THE HEAD THE LESS TURBO LAG. THE MORE DOWNSTREAM A TURBO IS, THE MORE THIS IS NOTICEABLE.
( HEAT- AN ELEMENT OF TURBINE EFFICIENCY IS REDUCED WHEN IT IS FARTHER FROM THE EXITING GASES IMMEDIATELY EXITING THE EXHAUST PORT)

SUPERCHARGERS: DOES NOT RESPOND WELL TO LONG OR EXTENDED EXHAUST SYSTEMS, X-PIPES OR POWER CHAMBERS…
KEEP IT SHORT AND IT WILL BE SWEET!

NORMALLY ASPIRATED: X-PIPES,CROSS-OVER OR BALANCE PIPE AND POWER CHAMBERS ARE GOOD.

IF YOU HAVE TO RUN MUFFLERS ON YOUR HEADERS, I HAVE TESTED A LOT OF “TRICK AND HI-TECH” MUFFLERS ALL THIS YEARS.
WE EVEN TESTED A POPULAR MUFFLER WITH A LETTER “F” AND WE LOST 3-4 /10ths AT THE DRAGSTRIP…
THE BEST- – - -THE OLD FASHIONED STRAIGHT THRU
“GLASS PACK TYPE”! SOME THINGS NEVER CHANGE……AMEN!

FOR ALL OUT “MATCH RACE COMPETITION”? an open header with the right size and length collector with no mufflers!!!

i HOPE I HELP SOME BY OPENING IDEAS AND IMAGINATIONS IN OUR QUEST FOR SPEED….

Feel free to post any questions on the comments below.