We made the conversion, installed a set of 72 jets, then ran a static test to see if we were in the ballpark. The dyno instrumentation showed we were lean. The bowls came off, and both outboard carbs were loaded with a pair of 80 jets. Another static pull showed the mixture to be close, and we were in business. Peak power output was up to nearly match the rpm, showing 534 hp at 5,600 rpm, but the peak torque was off the mark turned in by the box stock carbs, with 566 lb-ft at 4,000 rpm. The averages at 545.2 lb-ft and 444 hp showed that the 80 jets made virtually the identical output as the factory carb calibration. The Six Pack carbs seemed to be pretty close with jetting as delivered.
Next, we moved up to 82 jets in the outboard carbs. The engine liked the extra fuel, and output climbed to 573 lb-ft of torque at 4,100 rpm and 541 hp. Jetting up was definitely worth power on this combo over the factory carb calibration. The averages were also up handily, with the torque and horsepower numbers moving up to 551.4 and 450 respectively. The Six Pack was matching the average horsepower of the modern four-barrel induction and actually making more peak power up top. The edge in torque lower in the rpm range, however, went to the four-barrel by a small margin.
If some is good, more must be better, so we went back in a final time and stepped up the outboard carbs to 84 jets. We did see a slight gain in peak output with this change, posting 543 hp, our best number of the day, and a full 8 hp better than what was achieved with the single four-barrel. Torque was up a fraction at 573.1 lb-ft at 3,900 rpm. The averages were down just fractionally from the previous test-550.6 lb-ft of torque and 449 hp over the rpm range. The mixed results showed that the optimum jetting was somewhere between the two tests.
It was clear that we had reached a point of diminishing returns with further fattening of the carbs. With the QuickFuel metering plates, we were able to find 12 hp in our Six Pack induction with simple jet changes-a worthy gain by anyone's reckoning. We came away from the test more respectful than ever of the Six Pack's power-producing ability. The Performer RPM intake has proven itself in several of our tests as a spectacular power and torque producer on 440s at this power and rpm range. The tuned Six Pack, though not quite matching the torque numbers, edged it out in peak hp. Bear in mind that back in the day there was nothing in the league of the Six Pack. No wonder it stood head and shoulders above the crowd.
Installing the QuickFuel metering...
Installing the QuickFuel metering plate takes just minutes. Remove the bowl to get to the stock metering plate. Use a clutch-head screwdriver to remove the mounting fasteners. The QuickFuel plate attaches in its place with the supplied gasket, but without the stock sheetmetal stiffening plate. From here, changing the main metering jets is quick and easy.
The replacement plate is considerably...
The replacement plate is considerably thicker than the original, and float clearance is quite close. If it hits, the float can't stop fuel flow, and it will pour fuel out the vents and flood. Some floats will not clear if the parting line of the float is too pronounced. Make a safety fuel check to be certain there isn't a problem with hanging up the float on your carb if doing the conversion. Ours cleared.
When it was all said and done,...
When it was all said and done, our jetted Six Pack developed 543 hp and 573.3 lb-ft of torque. While torque was a little under the phenomenal numbers turned in by the Performer RPM, peak hp honors go to the Six Pack in this test. There's no denying that Mother Mopar's Six Pack was more than a pretty face.