SOURCE: MoPar Performance News, Tech Tips, by Larry Shepard - Mopar Chief
Engineer
The problem is related to the gasket that seals the cover to the bottom of
the manifold on the Magnum engines. If this gasket does not seal properly,
the engine can suck in oil vapors from the lifter valley and cause the
engine to detonate due to the aggressive spark advance curve used in the
Magnum computers. Remembering where this gasket is located, this is not
the first thing that you want to do. It could be expensive and time
consuming
to pull off the intake to check. However, we have a helpful tip. To
determine if there is a proper seal, remove the PCV (Positive Crankcase
Ventilation) valve from the right hand valve cover, but leave the PCV valve
attached to the hose from the intake manifold. Remove the breather hose
from the left-hand valve cover that goes to the air cleaner. Plug-off the
connection at the valve cover. With the engine idling, place your thumb
over the opening where the PCV valve was located. After 10-15 seconds you
should feel pressure, which indicates that the gasket is sealing. If you
feel a vacuum, the gasket is leaking and needs to be repaired. The best
repair is to remove the intake manifold, remove the bottom plate and
discard the failed or leaking gasket. Clean all the surfaces thoroughly,
and apply
a bead of Mopar RTV sealant, PN 82300235 to the bottom of the manifold.
Re-install the plate, let dry and then re-install the manifold. Refer to
the service manual for manifold installation tips and details.
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