could be the black tarry carbon build up in the intake and crossove is breaking loose and going into the motor. a piece might have wedged in a valve temporarily an d held it open. the crossover is realtively easy to remove and clean the heads are tricky to clean on the engine and i dont think any body has figured ou t how to do that at least that i have seen here. best solutio is valve job but tha t is a lot of $ prob 1500 + depending on the "while werre in there "stuff.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.