Tuning a tunnel ram intake with dual carburetors can seem daunting, but with the right guidance, it can be a rewarding experience. This guide focuses on Edelbrock’s popular 2×4 setup, offering insights into initial setup, jetting, and timing adjustments for optimal performance on a small-block Chevy.
Edelbrock’s 2×4 intake manifold kit (EDL-20254), featuring dual 500 cfm Endurashine carburetors, is a popular choice for enthusiasts seeking increased horsepower on their small-block Chevys. While this kit comes pre-configured, understanding its nuances and potential tuning adjustments is crucial for maximizing its potential. This guide will walk you through key considerations for dialing in your Edelbrock 2×4 setup.
Understanding Edelbrock 2×4 Jetting and Metering Rods
One key difference between a single four-barrel and the Edelbrock 2×4 setup lies in the jetting and metering rods. Out of the box, a single Edelbrock carb typically uses an 86 primary jet with a 65×52 metering rod and 95 secondary jets. The 2×4 system, however, utilizes a leaner configuration to compensate for the increased airflow from the dual carburetors. Edelbrock recommends a 65×57 primary metering rod and 77 secondary jets for the 2×4 setup.
The metering rod system in Edelbrock carburetors plays a crucial role in part-throttle fuel delivery. Under light throttle and high manifold vacuum, the metering rod sits lower in the jet, restricting fuel flow. At wide-open throttle (WOT), vacuum drops, allowing the metering rod to rise, exposing more of the jet and increasing fuel flow. The 65×57 rod in the 2×4 setup has a larger diameter on its tapered end, effectively leaning out the cruise mixture compared to the 65×52 rod found in single four-barrel applications.
Ignition Timing: A Critical Factor
Beyond carburetion, proper ignition timing is paramount for optimal performance and drivability with a tunnel ram setup. Many enthusiasts overlook this crucial aspect. While a stock small-block might run well with 6-8 degrees of initial timing before top dead center (BTDC), a modified engine with aftermarket heads and camshaft often requires significantly more initial timing—typically in the 14-16 degree BTDC range.
Total timing advance, measured above 3,000 rpm, should also be considered. Aim for a total timing of around 34-36 degrees BTDC. If your total timing is off, adjust the initial timing or modify the distributor’s mechanical advance curve to achieve the desired total timing figure. This often involves changing bushings or springs within the distributor.
Fine-Tuning Your Edelbrock 2×4
While the Edelbrock 2×4 system generally performs well with its out-of-the-box settings, fine-tuning can further optimize performance. The accessibility of the metering rods makes experimentation relatively easy. By simply loosening a screw, you can access and change the metering rods without disassembling the carburetor.
For example, switching to a 67×55 metering rod combination will lean out the cruise mixture further while enriching the WOT mixture slightly. Remember to meticulously document any changes made, allowing you to revert to previous settings if needed.
Conclusion: Achieving Optimal Performance
Tuning a car craft tunnel ram with an Edelbrock 2×4 setup involves understanding the interplay between jetting, metering rods, and ignition timing. By following the guidelines outlined in this guide and making careful adjustments, you can unlock the full potential of your engine, achieving optimal performance and drivability. Remember to systematically document your tuning changes and to proceed with small, incremental adjustments for the best results.
