I've had this van for 20 years now. I'm no mechanic but over the years I've changed everything in it at some point, and finally the lower intake gasket that covers the lifter valley failed and dumped all my coolant into the oil pan.

So 6 months later I get my block back from the machine shop and I'm rebuilding. I got my Chilton's and YouTube. Everything seems to be coming along fine. Everything has a funny retorque sequence. Book always says before installing, chase threads with a tap. I've been checking the holes and dry fitting every bolt to see if anything has been buggered up or had any unusual resistance and haven't had any problem until installing the upper intake manifold.

The upper intake manifold does not touch any liquid. The bolts bolt into aluminum. There shouldn't be any corrosion, maybe some galvanic bs from the bolts being steel and the lower intake they bolt into being aluminum, but the bottom half of all of the bolts have some red flakey substance on them, all of the holes are massively buggered up, and after chasing them with a tap, none of the bolts will torque past hand tight. They just spin.

Tldnr: Did the guys who had it before me mess up the threads and just thread lock them back in? Upper intake only touches incoming air and possibly reburn exhaust, is the seal all that important? Has anyone heard of this practice, is this common?

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