Hmmm, puzzling indeed. With regard to the minimum shaving to true the heads, might there have been work done before you owned the car? Just thinking out loud, possibly some prussian blue on one surface, say the head intake surface, then bolt the manifold down without the valley pan and see if the bluing is transferred equally to all surfaces of the intake? I really don't think this is the problem, but the bluing is a quick and dirty check. You sound very knowledgeable, so know that I am only trying to get back to basics here, not preach to the choir. If it were my engine I would first time by vacuum gauge, specifically to see how high you can get the vacuum. 13" is low and 15" is not very high unless you have a long duration cam or a lot of overlap. Second, I would dump the Petronix and try a conventional distributor. The distributor seems to be the only constant left, and you said the car runs poorly. Bad ignition, and retarded ignition could account for both low vacuum and rich running. This is a relatively easy test to make. The Petronix unit could be bad, I actually have had symptoms similar to what you describe with a 1992 Jeep Grand Wagoneer when the ignition module would begin to fail, which it did on a regular basis before I learned about system grounds. >Other possibilities are flattened cam lobes, this is a problem more >and more, it seems, with the zinc compounds being removed from oil. > >Plugged exhaust, not likely, but easily checked with a vacuum gauge >while the engine is loaded. > > ------------------------------------ To send a message to this group, send an email to: Chrysler300@xxxxxxxxxxxxxxx For list server instructions, go to http://www.chrysler300club.com/yahoolist/inst.htm For archives go to http://www.forwardlook.net/300-archive/Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Chrysler300/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/Chrysler300/join (Yahoo! ID required) <*> To change settings via email: mailto:Chrysler300-digest@xxxxxxxxxxxxxxx mailto:Chrysler300-fullfeatured@xxxxxxxxxxxxxxx <*> To unsubscribe from this group, send an email to: Chrysler300-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/