The supposed 402BB in this truck I got has closed chamber heads. In search of the mystery noises, I pulled a valve cover, finding out that this is the grungiest motor I have ever seen. After some scraping, I got the casting number. 3917215 which according to Mortec are '67-'68 Oval port, closed chamber 396 or 427 heads. The motor is still running like garbage, has a bad miss and deathly rattle, but after retarding the timing back closer to where it should be, I was able to powerbrake the truck (a dually rear crew cab with a utility box) in my driveway. /forums/images/graemlins/grin.gif Still pings some, but if this motor is say a higher compression motor, and I have very low octane fuel in it, I suppose it still will.