57421C4 - Bassani Exhaust

1986-1991 C4 Corvette “421” series headers
57421C4
Note: anti-seize
should be applied
to all fastener
threads, pipe slip
joints and mating
surfaces of
ball /socket
connections.
Parts List and Description
(A)
(B)
57421C4L
57421C4R
57421C4A
-left side header
-right side header
-adapters w/flanges (2, not shown)
Hardware List
12
2
2
2
4
4
4
1
1
-3/8” header bolts
-header gaskets
-5/16 x 1” bolts
-5/16 flanged nuts
-3/8” x 2.5” bolts
-3/8” flat washers
-3/8” flanged nuts
-EGR gasket
-anti-seize compound
Note: The installation of these headers requires the removal of the warm-up catalyst (pre-cats) on vehicles so equipped. Because of
this, these headers not legal for or intended to be used on street-driven, pollution controlled motor vehicles. These headers may be
installed with an available Bassani “Y” pipe (part no. 5786913) to allow for a bolt-in installation with the stock center main catalytic
converter.
Installation Instructions:
1.) Disconnect negative battery cable.
2.) Raise hood and disconnect spark plug wires and spark plugs from engine.
3.) Disconnect EGR tube from passenger side exhaust manifold.
4.) Remove oil dipstick tube from engine.
5.) Disconnect exhaust system from manifolds.
6.) Remove air injection hoses connected to one-way check valves on manifold air injection tube assemblies.
7.) Remove check valves from end of air injection tube assemblies.
8.) Remove bolts attaching exhaust manifolds to engine and remove manifolds with tube assemblies from vehicle.
9.) Install new headers through bottom of vehicle and attach to engine using supplied gaskets and bolts.
10.) Apply anti seize compound to threads inside one-way air injection check valves and install on headers.
11.) Reinstall oil dipstick, spark plugs, and spark plug wires.
12.) Attach EGR tube on engine to flange on passenger side header with supplied gasket and 5/16” hardware.
13.) Attach supplied 2.5” collector adapters with flanges to headers with supplied 3/8” hardware. Weld any custom
exhaust of your choice to end of header adapters or proceed to next step.
14.) If you also purchased the compatible Bassani “Y” pipe to install with these headers (part no. 5786913), The adapters
will not be required and may be discarded.
15.) Reconnect negative battery cable and close hood.
FOR TECHNICAL ASSISTANCE CALL TOLL-FREE (866) 782-3283
2900 East La Jolla Anaheim, CA 92806
9/19/06