Edelbrock C-26 Small Block Chevy Dual-Quad Intake Manifold Installation Instructions

Edelbrock C-26 Small Block Chevy Dual-Quad Intake Manifold Installation Instructions
For 1957 to 1986 Non-EGR Chevrolet 262-400 c.i.d. V8
Catalog #5425 & #7525
PLEASE study these instructions carefully before beginning this installation. Most installations can be accomplished with common tools and
procedures. However, you should be familiar with and comfortable working on your vehicle. If you do not feel comfortable performing this
installation, it is recommended to have the installation completed by a qualified mechanic. If you have any questions, please call our Technical
Hotline at: 1-800-416-8628, 7:00 am - 5:00 pm, Pacific Standard Time, Monday through Friday or e-mail us at Edelbrock@Edelbrock.com.
IMPORTANT NOTE: Proper installation is the responsibility of the installer.
Improper installation may result in poor performance and engine or vehicle damage.
DESCRIPTION: The C-26 (#5425) manifold combines two small four-barrel carburetors with a dual plane manifold layout to achieve the best
balance of drivability, great looks, and outstanding performance for muscle car, street rod and marine applications. #7525 features an Air-Gap
design, separating the runners from the engine valley for a cooler, denser air charge. It stands 1-5/8” taller than the 5425 and its larger runners
offer performance improvements in the 1500-6500 RPM range. Edelbrock has developed special air filters for these manifolds. To give your engine
the ultimate custom look, the polished aluminum Elite Series oval air cleaner #4235 is suggested. Chrome oval air cleaner #1235 or two #1209
(6" round) Pro-Flo air cleaners are also available. Please note Bracket section below for your particular installation.
ACCESSORIES & INSTALLATION ITEMS: Major recommendations are listed below. See our catalog for details. To order a catalog, call
(800) FUN-TEAM, or visit www.edelbrock.com.
EGR SYSTEMS: These intake manifolds will not accept stock EGR (Exhaust Gas Recirculation) equipment. EGR systems are used on most
1972 and later model vehicles. Check local laws for requirements.
THROTTLE & ACCESSORY BRACKETS: The throttle and kickdown bracket on some vehicles may require modification to fit. These manifolds
will not accept 1968 and earlier alternator bracket assemblies and have no provision for ignition coil mounting. Manifold #5425 is machined
to accept front (early style) oil filler tube. If not used, plug the hole with a 1-1/4" freeze plug. Use progressive linkage kit #7094 to connect
the carburetors together (See “Carburetor Recommendations”).
CARBURETOR RECOMMENDATIONS: Use two manual choke carbs (Two 1404’s or two 1804’s), or one manual and one electric choke (1403
& 1404, or 1803 & 1804, if electric choke is desired). Note that the Thunder Series carburetors listed under manifold #7525 are calibrated
specifically for the 7525 manifold, and in most cases, will not require additional tuning. For manifold 5425, see “Prep and Tuning for Power”
for additional tuning information.
Performer #1403 (500 cfm)
Performer #1404 (500 cfm)
#7094 Dual Quad Throttle Kit, #8088 Dual Quad fuel line kit
#7094 Dual Quad Throttle Kit, #8088 Dual Quad fuel line kit
#7094 Dual Quad Throttle Kit, #8088 Dual Quad fuel line kit
#7094 Dual Quad Throttle Kit, #8088 Dual Quad fuel line kit
Thunder Series #1803 (500 cfm)
Thunder Series #1804 (500 cfm)
NOTES: Carburetors each require #8008 or #8024 stud, washer and nut kit. Determine proper length based on gasket thickness and your
accessory mounting requirements. If two manual choke Performer Series Carburetors are used and electric choke is desired later on, they can be
converted to electric choke using Electric Choke Kit #1478. Use electric choke on the rear carburetor ONLY. Manual choke Thunder Series
carburetors CAN NOT be converted to manual choke. If electric choke is desired with Thunder Series carburetors, a manual choke carburetor
should be used in the front and an electric choke carburetor should be used at the rear.
Catalog #5425, 7525
Rev. 9/07 - AJ/mc
Page 1 of 2
©2007 Edelbrock Corporation
Brochure #63-0145
GASKETS: Do not use competition-style intake gaskets for this street manifold. Due to material deterioration over time, internal leakage of
vacuum, oil, and coolant may occur.
DISTRIBUTOR: Due to the runner layout of the Air-Gap dual quad manifold (#7525), the use of an HEI distributor may require some light
clearancing work prior to installation. The Endurashine coating (#75254) will exacerbate this issue and the use of an aftermarket distributor
is strongly recommended to avoid damaging the finish.
5425, 7525
Edelbrock #7201 Port: 1.28” x 2.09”, .060” Thickness
NOTE: To ensure maximum performance and a proper seal, Edelbrock gaskets which are
specifically designed and manufactured for use with Edelbrock parts must be used.
NOTE: Please refer to Edelbrock Performer Series Carburetor Owner’s Manual for detailed tuning procedures.
1. The 5425 manifold will produce optimum power and drivability when used with #1404 carburetors. Edelbrock has found, while dyno
testing our Performer 350ci (310hp) crate engine at our location, the best calibration to be: Metering Rods - .065” x .052”, Primary Jets
- .086”, and Secondary Jets - .095”. The 7525 manifold will see optimum performance with the use of 1804 carburetors. The 1804
carburetors are specifically tuned for the 7525 manifold and the stock calibration should be used. Calibrations will vary according to
engine build and atmospheric conditions. Use these recommendations as a starting point. Further tuning may be necessary.
2. Aftermarket distributor curve kits may be used with this intake manifold.
3. Use modified or high performance cylinder heads such as our Performer or Performer RPM.
4. Installation of aftermarket headers, camshafts or both may lean carburetor calibration. Should this condition occur, recalibrate with a
richer jet.
CAMSHAFT AND HEADERS: Dual Quad manifolds are compatible with aftermarket camshafts and headers. Header primary tube diameter
should be 1-5/8” to 1-3/4" depending on the specific engine combination. Edelbrock has developed two camshafts for use with this intake
manifold - Performer-Plus #2103 or Torker-Plus #5002. Please check the catalog or website for rpm and application guidelines.
Use only recommended intake gaskets set when installing
this intake manifold.
Fully clean the cylinder head intake flanges and the engine
block end seal surfaces.
Apply Edelbrock Gasgacinch sealant P/N 9300 to both
cylinder head flanges and to the cylinder head side of the
gaskets, allow to air dry, and attach the intake gaskets.
Do not use cork or rubber end seals. Use RTV silicone sealer
instead. Apply a ¼" high bead across each block end seal
surface, overlapping the intake gasket at the four corners.
This method will eliminate end seal slippage.
Install the intake manifold and hold-down bolts. Torque all of
the manifold bolts in two steps by the sequence shown in
Figure 1 to 25 ft/lbs.
Figure 1 - 262-400 c.i.d. Small Block Chevy Torque Sequence
Torque Bolts to 25 ft/lbs.
Firing Order: 1-8-4-3-6-5-7-2
Turn Distributor Counter-Clockwise to Advance Timing
Edelbrock Corporation • 2700 California St. • Torrance, CA 90503
Tech Line: 1-800-416-8628 • E-Mail: Edelbrock@Edelbrock.com
Catalog #5425, 7525
Rev. 9/07 - AJ/mc
Page 2 of 2
©2007 Edelbrock Corporation
Brochure #63-0145
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