The CH-28 intake is designed with a tight 6 7/16-inch center-to-center spacing and the narrow 4 1/4-inch bolt pattern, so carburetor choices are limited to the AFB or AVS. Of course, a pair of original Carter carbs would look just perfect on a classic Mopar engine, but since Carter carbs are no longer available we opted for a pair of the very similar looking Edelbrock AVS Thunder Series carbs. We used a pair of PN 1804 carbs, which are rated at 500 cfm and are calibrated by Edelbrock for dual-quad applications. Edelbrock actually recommends a pair of the slightly larger 600-cfm carbs for a 500ci engine, so it is possible that we left a little power on the table.

On the Dyno
The first order of business on the dyno was to check the cranking compression. We always check the cranking compression on new combinations in order to give us a baseline that we can keep track of over time. We considered it a good omen when all eight cylinders cranked right at 225 psi with very little variation between them. Our plan was to run all tests with the ignition timing at 36 degrees of advance, so we played it safe and used race gas.

The 505 fired right up and sounded very smooth on the dyno with the dual-carb setup. In fact, it sounded so smooth, the dyno operator didn't think we would make much power with this combination. He changed his mind after the first pull spun the needle well into the 600hp range, though. We made a couple of quick adjustments to the carbs in order to richen them up at full throttle, and then made a series of dyno pulls to fully test this combination. We ended up with an average peak power of 615 hp at 5,800 rpm, and a peak torque reading of 611 lb-ft at 4,800 rpm. As expected, the combination of a dual-plane intake with the smaller-port cylinder heads made this combination more of a torque monster than a power king, but that is exactly what we wanted. The hydraulic-roller camshaft made excellent power and had a nice, smooth idle. We ran the engine 500 rpm past the power peak to test the shifting point without observing any sort of valvetrain instability from the hydraulic lifters.

All in all, we were very pleased with the power that this combination made on the dyno. 615 hp in a 3,700-pound car would give a 6.1:1 weight-to-power ratio, which is enough power to run low 10s in the quarter-mile at 125 mph. So that is really getting with the program for an engine combination that should be easy to maintain. We haven't had time to get this engine into a car yet for some track duty, but based on the dyno performance we would expect this engine to be a ton of fun on the street. The high compression is the only thing that would put a damper on the street driving, but that can be corrected next time the short-block is freshened up.

Intake Upgrade
Mopar Performance recently introduced a high-rise dual plane intake manifold in their catalog for the 440 engine. The part number for this high-rise intake is 5153525, and it is only available for the 413/426/440 RB engines. This intake is almost identical to an Edelbrock Performer RPM intake, but it has a cool looking Mopar Wedge script cast on the front. We thought it might be interesting to try the Mopar intake on our 505-inch motor while we had it on the dyno, just to see how the new high-rise design stacks up against the older CH-28. We picked a Holley 1,000 HP carb to run on top of the Mopar intake in order to keep the rated cfm similar between the two dyno tests. The 1,000 HP carb has a 1.560-inch venturi with a contoured main body, screw-in air bleeds, and downleg boosters. These HP carbs usually work great right out of the box on a motor like this, and this one was no exception. We made one jet change from 84 to 86 size jets in all four corners, and that was all the tuning we had to do.