One common yet lesser-known issue with these Magnum motors is that the plenum seal tends to fail. The two-piece intake has a plate that keeps the intake charge from the oil in the lifter valley, but the plate is thin sheetmetal, and over time the seal can blow out. That results in oil in the intake, fouled plugs, poor idling, and more. Hughes Engines has come up with a solution in the form of a 1/4-inch-thick CNC-machined plate and new seal that will keep the oil from the air for the foreseeable future. The kit includes the aluminum plate, a new plenum seal, new intake manifold seals, new intake manifold bolts, and new plenum bolts (p/n HUG-7714).