273 Cracked Intake manifold with a belly of "Charcoal"!

[JDMopar]

It's normal for oil splashed around by the lifters and pushrods to seep under that tin plate, and then get baked to a crisp by the heat radiating from the exhaust crossover that you mentioned. There is no exhaust escaping into the lifter valley under normal circumstances. The crack you mention is probably in that crossover and only added the crunchiness to the trapped and baked oil that seeped around the unsealed edge of the tin plate riveted to the bottom. There's bound to be someone around Tucson who would give you a 318 2 barrel intake for free, to get you by until a permanent and proper fix can be done. And yes, the 318 intake newer than 65 WILL bolt on and work fine. Just use washers under the heads of the bolts, and use sealer on the threads of the bolts like should be done on any small block Mopar intake. The sealer on the threads of intake bolts keeps oil from wicking up the threads and ponding up in the bottom pockets between the intake bolts.

 

[RustyRatRod]

There's nothing happening in an alternate universe here. The burnt, crusted and chunked up oil is called sludge. Whether it's wet and gooey, or dried and chunky. It's from one thing. Failure to change the engine oil frequently enough. Simple as that.