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Message: [QUOTE="Maryland dieselnick, post: 1272316, member: 22661"] I was referring to the regen shakes some 6.7s experience. It is caused by some engines having valve guide to stem clearances that are too tight. During regen, the exhaust valves get blast furnaced during the exhaust stroke. This heat causes thermal exhaust valve stiction. This stiction is not a seize. It is a stiction. The valve geometry is a strait up and down. The piston actually impacts the valve knocking it free from its static state. Due to the geometry used this event does not put lateral force on the valve, so this collision is not immediately catastrophic. Most that have stem clearances that are too tight will develope the the violent regen shakes in the 3k-20k range. Ford's first attempt to rectify this was to remove your cab and left head. Then the valve stems were to be cleaned and reinstalled. Trucks would come right back after this was performed. Anytime back pressure exceeds atmosphere, exhaust gasses will escape vent right up those exhaust guides. These gasses will leave a film. This is normal for all engines. Some heads came thru with guide bores that created stem clearances that are too tight. The exhaust valves used can be purchased for $7 and change from a vendor that sells for 10 .percent over cost. During this blast furnacing of this valve with temps reaching over 1400 degrees it experiences thermal expansion. This thermal expansion causes this stiction. There are over thirty cases I'm aware of. Many trucks have been put thru the Lemmon law process. Ford went from the stem cleanings to issuing a TSB saying if a customer came in with this condition to put the TSB in the customers hands stating it is a normal condition. This is after they had made statements engineers were aware of the problem and we're working on a fix and after the stem cleaning campaign. There is a case on the diesel stop and ford truck enthusiast. The repair order has the mechanics notes stating they were too tight and that was on his bench at room temp. backing up my failure analysis for those looking for corraberation. Again fellas I mean no harm or anything like that at all and hope I'm not viewed that way. [/QUOTE]