Get Shorty:  Factory Exhaust Manifolds vs. Hedman Hedders Shorty Headers

After last month’s throttle body spacer dyno tests (August 2014, Spaced Out:  Testing Hamburger’s Throttle Body Spacer) provided a minimum performance increase, this month’s testing will focus on the exhaust.  A pair of headers will be installed with the hopes of increasing the overall torque and horsepower, taking better advantage of the TB spacer, and maintaining the excellent drivability.  Penn College was able to acquire a pair of Hedman Hedders “shorty” headers for the college’s 2006 5.7L Hemi Dodge Charger.

The Setup for Testing the Headers and TB Spacer
The tests planned for this series of dyno runs consist of a minimum of three baseline runs, three Hedman Hedders runs, and three Hedman Hedders and Hamburger’s TB spacer runs.  Once all the tests are run the Charger will be returned to the baseline trim for three more runs.  This test is an ABCA test series.  Provided that all three runs are within 1% of each other at each step of the testing and the baseline runs pre- and post are the same, the results of the testing will be considered valid.  If the pre- and post-baseline runs are not the same the results from the components installed cannot be verified until the reason for the difference in the pre- and post-baseline runs can be determined and repaired.  Once the repaired the testing must start over with three valid baseline runs.

Baseline
To establish a baseline for the performance upgrades the Charger was tied down to the Penn College Mustang chassis dyno.  The baseline runs were identical to previous baseline runs performed with the Charger in an all stock setup so the previous baseline numbers were used.  The baseline results were established by running the Hemi at WOT from 2800 rpm to 5500 rpm.  The Hemi produced 296.8 lb/ft of torque at 4400 rpm and 275.0 horsepower at 5200 rpm.  Over the rpm sweep the average torque was 280.0 lb/ft and an average of 223.3 horsepower.  Through the entire rpm sweep the exhaust backpressure remained below 1 psig.  With a solid baseline established, now it was time to install the Hedman Hedders shorty headers.

Hedman Hedders
The Hedman Hedders to be tested were a pair of shorty headers (part no. 72500); visit www.hedman.com to find the headers that will fit your application.  The headers are a true bolt-on T.E.M.S. (tm) Tubular Exhaust Manifold System constructed of 304 stainless steel with laser cut 3/8” flanges and 18 gauge mandrel bent 1½” primary tubes.  Included with the headers were gaskets and all the new mounting hardware necessary to complete the installation.  While there are options for ceramic coatings on the headers the natural (uncoated) finish was selected for the Charger.  These headers are designed for automatic transmission equipped vehicles only.  As of the writing of this article this header has been submitted to the California Air Resources Board for criteria and exemption approval. Pending approval, the E.O. # should be available soon.

The removal of the factory exhaust manifolds began with the disconnecting of the negative battery cable.  The Charger had to be raised off the floor at least 36 inches and supported on four jack stands or if you have access to a vehicle hydraulic lift that would be even better.  With the vehicle securely supported the belly pan was removed from the chassis.  The stock y-pipe downstream O2 sensors were disconnected and the fasteners were removed to allow the removal of the y-pipes.  Depending upon the amount of accumulated rust and debris the use of a penetrant spray may be necessary to ease the disassembly process.  Once the y-pipes were free of the car they were carefully placed aside for later use.  Now with better access to the factory manifolds the heat shields had to be removed from each manifold.  The shields are held in place by four nuts per shield; again, penetrant spray may be necessary to help break the nuts loose from the studs.  Once the nuts were removed the dipstick tube was removed from the passenger side of the engine bay.  At this point the shields had to be wrestled out of the engine bay, this was a difficult process as the real estate is at a premium around the exhaust manifolds, the shields had to be bent a bit to remove them from the car.  The removal of the upstream O2 sensors may provide a bit more clearance when removing the heat shields.  The removal of the factory exhaust manifolds required a plethora of sockets (deep and shallow well), extensions, swivels, and wrenches to reach every fastener.  Once the manifolds and gaskets were removed from the engine bay the upstream O2 sensors where removed from the manifolds (if not previously removed), dabbed with a touch of anti-seize, and threaded in the new headers.

The installation of the passenger side header required reusing one factory fastener with a spacer supplied with the headers.  This fastener attaches the dipstick tube via a stud.  The exhaust gasket was held in place on the cylinder head with a dab of RTV and the previously mentioned factory fastener was threaded in a few threads into the most forward bolt hole (#1) in the head.  Along the top row of the cylinder head new fasteners where threaded a few threads into bolt holes (#2) and (#3).  There are cut outs on the header flange that allowed the header to be slipped into place between the gasket and the washers (or spacer) on the fasteners.  The rest of the supplied fasteners were threaded into place and all the fasteners were torqued to 16 ft-lbs following the torque sequence found in the service manual.  The dipstick tube was reinstalled into the oil pan, the mounting tab was placed over the stud on fastener (#1), and the factory nut was tightened to lock the dipstick tube into place.  The driver side header followed the same procedure with the exception of the installation of the dipstick tube.

The upstream O2 sensors where reconnected.  The y-pipes where slipped back into place and secured with new fasteners at the header flange and the factory clamps on the down pipe.  The downstream O2 sensors were reconnected.  A quick check for any interference of any electrical wires, fuel lines, and AC lines was made and the belly pan was reinstalled.  Once the Charger was back on the ground the negative cable was reattached and the engine was started.  With the engine running and up to operating temperature a check was made for leaks, noises, and “check engine” lights; none were found so the Charger was backed onto the dyno for more runs.  Expect the header installation to take the better part of a Saturday afternoon if everything comes apart smoothly.

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