A most difficult thing in racing engine development is to understand fuel distribution among the cylinders and get it correct in the engine at the race track. Fuel distribution is also an area where small changes can result in big gains or big losses. The only accurate way to determine what these small changes should be is to use a dynamometer with mixture level analysis on each cylinder. The purpose of this tune-up manual is to relay to the racers the fuel distribution information accumulated over the years from Chrysler dynamometer development programs.
Fuel distribution is the cylinder-to-cylinder variance in fuel-air ratio. It is desired that the cylinder not be too lean or too rich and that all the cylinders be the same fuel-air ratio through the engine speed range. It is obvious from this that the carburetor and intake manifold work as a team. A stock carburetor that works well on a stock manifold may not work well on a race intake manifold. A race carburetor that performs well on a race manifold may perform poorly on a stock manifold.
In most cases, drag racing requires certain changes to be made to any carburetor and special manifold modifications to go with the carburetor that is to be used. These modifications have been determined on the dynamometer for the best overall engine output for Super Stock, Modified Production and Bracket racing. The most popular racing packages with the commonly available manifolds will be covered by engine family, i.e. 6 cylinder, LA engine, B engine, RB engine and Hemi.
This revision supersedes all previous information. This bulletin represents the latest developments that our dynamometer and drag strip testing have shown to work. Many carb-manifold packages are left in for reference only. It's the latest information that we may have on an out-dated package.
A. C. Nichols & L. S. Shepard Staff Engineers
------------------------------------------------------------------------- Package: 4 Barrel Set-Up General Multi-Purpose Carburetor: Holley List 6299 Manifold: Offenhauser Aluminum 4 Barrel PN P3690801 Manifold Modifications: None Carb Specifications: 390 cfm Holley, vacuum secondaries Primary Jet: #49 Secondary Jet: #52 Power Valve: 25R-591A-65 PV Channel Restriction: .052 Idle Air Bleed: .078 High Speed Bleed: .043 Diaphragm Spring: Yellow -------------------------------------------------------------------------
This is the best general purpose four barrel setup for the 6 cylinder engines.
------------------------------------------------------------------------- Package: 4 Barrel Set-Up Race Only Carb: 4 Barrel Holley List 7191 PN P3690930 Manifold: Offenhauser Aluminum 4 Barrel PN P3690801 Exhaust Heat Blocked Manifold Modifications: Car mounted with primaries toward the front of engine. See Figure 21-1. Carb Specifications: 600 cfm Holley, double pumper dual feed with mechanical secondaries - Manual Choke Throttle Bore: 1-9/16 x 1-9/16 Venturi: 1-1/4 x 1-5/16 Primary Jet: #64 Secondary Jet: #72 Power Valve Channel Restriction: .046 Power Valve: No. 65 Pump Shooter: Primary - .025 Secondary - .021 -------------------------------------------------------------------------
Note: For general multi-purpose or brackets, the previous carb set-up is recommended. This package is for all-out racing only.
------------------------------------------------------------------------- Package: 2 Bbl. Set-up with Headers Carb: 2 Bbl. Carter BBD-81375 Manifold: Production Aluminum Manifold Modifications: None required. Carb Specifications: Throttle Bore: 1-7/16 Primary Jet: 2 Steps Richer Venturi: 1-1/16 Secondary Jets: N/A -------------------------------------------------------------------------
------------------------------------------------------------------------- Package: Hyper Pak Four-Barrel Carb.: Carter AFB 3083 PN 2129881 (No Longer Available) Manifold: Chrysler Aluminum Hyper Pak (No Longer Available) Manifold Modifications: See Figure 21-2. Carb Specifications: Carter AFB Throttle Bore: 1-7/16 x 1-9/16 Venturi: 1-1/16 x 1-1/4 Primary Jet: 120-389 (.089) Throttle Side Choke Side Secondary Jet: 120-350 (.050) 120-365 (.065) WOT PT Metering Rod: 16-51 (.060 x .065) Float Setting: 9/32 Inverted - Measured from float bottom to gasket. Accel. Pump Shooter: .028 Idle Feed: 035 -------------------------------------------------------------------------
Special Note: This carb and intake manifold system has the primaries of carb facing toward the engine See Figure 21-2.
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