There are some premium rubberized cork and also silicon rubber seals which might help. Beyond that, the cast Aluminum Mopar Performance valve covers are a likely improvement. I bought a set of them and they're really nice. The do have the same lack of an additional port, but the casting is flat where the tube would go, so it can be milled out.
One of the Vanners here posted a very long time ago that he obtained success at preventing leaks by permanently adhering a rubberized cork seal right onto the heads, then permanently adhering a silicon seal to the valve covers. Each seal then only had one surface it had to work against, rather than both surfaces at once. The rubberized cork seal additionally acted as more of a dam against oil flowing out of the rocker assy area.
-It's been such a LONG TIME... BlueShift>>
1981 Dodge Ram B250 Custom Sportsman Maxi Van
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