Edelbrock 6643, 4743, 6743 user manual
Pro-Flo Header
1999-2000 Honda Civic Si
Catalog PNs 6643, 6743, 4743
Please study these instructions carefully before installing your new Pro-Flo Header.
They provide general guidelines to be studied and understood before you remove your stock
system. Failure to follow these instructions may void your warranty. If you have any questions or
problems, please contact our Technical Hotline at : 1-800-416-8628 from 7 am – 5 pm,
Monday through Friday, Pacific Standard Time.
DESCRIPTION: Edelbrock Pro-Flo header components are designed to improve the exhaust
efficiency of the Honda Civic 1.8L engine. A performance gain can be expected with the
installation of the system. This system requires no welding for installation and retains all stock
emissions equipment.
Suggested tools needed for installation: This vehicle has some metric fasteners.
• 3/8” ratchet socket set with extensions and a good assortment of metric sockets
• Combination wrenches (metric)
• Universal 12mm and 14mm swivel sockets
• Jackstands, screwdrivers, pliers, crescent wrench, etc.
• Liquid penetrant (GM #1052627 or equivalent); anti-seize compound (GM #5613695 or
equivalent)
SPECIAL NOTICE: This Edelbrock part has received an Executi ve Order number (E.O. #) from
the California Air Resources Board (C.A.R.B.) making it legal for street use on pollution-controlled
motor vehicles in all 50 states. To assist you with emissions equipment certification, we have
included a silver fan shroud decal to help testing personnel verify that this part is a legal
replacement part on the vehicle for which it is cataloged. The adhesive-backed decal should be
affixed to your fan shroud next to the existing emission and engine specification decal. Do not
cover your original equipment specification decal with the Edelbrock fan shroud decal.
WARNING: The use of “Thermal Wrap” or any aftermarket coating process will void the
warranty on your Pro-Flo header. Those products can cause excessive heat and moisture build up
resulting in corrosion and early failure of the system.
DISASSEMBLY:
1. Disconnect battery negative cable from battery.
2. Raise vehicle and support with jackstand.
3. The use of penetrating oil when removing and the use of anti-seize compound when
installing nuts and bolts will prevent the possibility of broken or stripped nuts and bolts.
4. Make sure converter is cool.
DISASSEMBLY (Continued)
5. Remove O2 sensor (if applicable) being careful not to destroy or rupture the unit.
Warning: Do not clean this unit in any cleaning solvents and do not rupture
wire.
6. Remove the two nuts from hanger bracket. Remove the two bolts and springs at the
catalytic converter. Then unbolt the three bolts at the mid-section of manifold and
remove lower portion of manifold (B-section).
7. Remove the bolt that is attached to the engine block in the lower section of manifold.
Remove bolts from manifold at cylinder head and pull manifold out from top side.
Note: Save all factory nuts, bolts and springs to be used during re-assembly.
ASSEMBLY
1. Install (a section) of header assembly from top side with gasket and 9 hardened
washers (supplied in kit), using factory bolts/nuts as applicable.
2. Install secondary section (B section) to (A section) top half using the three 10mm. Bolts
and lock washers with the two crush ring gaskets (all supplied in kit). Use anti-seize on
threads. (The two crush rings should be installed with the seam or split down towards
B-section).
3. With donut in place, connect header to catalytic converter using stock hardware as
before.
4. Install O2 sensor “if equipped”. Use anti-seize on threads of sensor and torque to 30 ft.
lbs.
PARTS LIST
Part Numbers Qty. PN Description
1 25-9187 Pro-Flo Header (A Section)
6643
1 25-9189 Pro-Flo Header (A Section)
6743 1 25-9197 Pro-Flo Header (B Section)
1 25-9185 Pro-Flo Header (A Section)
4743 1 25-9195 Pro-Flo Header (B Section)
1 25-9196 Pro-Flo Header (B Section)
1 22-6852 Installation Kit
1 22-6852 Installation Kit
1 22-6852 Installation Kit
Edelbrock Corporation
2700 California Street
Torrance, CA 90503
Tech Line: (800) 416-8628
E-Mail: Edelbrock@edelbrock.com
©2001 Edelbrock Corporation
Rev. 5/01
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