The MDS Solenoids In Your 5.7 HEMI Help Conserve Fuel Chrysler HEMI engines with MDS each contain four solenoids. You can find them bolted into the cylinder head beneath the air intake manifold.

The original 426 HEMI had 4.25-inch cylinders and a 3.75-inch crankshaft stroke, which pencils out to 425.6 cubic-inches using the formula to find the volume of a cylinder and multiplying by eight.

As the HEMI has aged, emissions standards have gotten stricter, and for the 2024 model year, this engine was phased out. The Ram 1500 replaced it with the Hurricane, a new, smaller engine.