how often should i run the valves on my twelve valve cummins ? had it done last time, would you happen to have a step by step

This should get you covered... http://www.dodgeram.org/tech/dsl/maint/2nd_Gen-12v.htm 12V require more valve adjustment that 24V... But here is my write up for a 24V and it really close to the 12V... http://mopar.mopar1973man.com/tips/cumm ... ve-adj.htm

The book says 30k. The book says that wide tolerances are OK. As for the wide tolerances - you have the stuff out, might as well do it +- .001As for the mileage - I have always run way past. I keep fuel records, with a 5% drop in MPG I will be looking for the cause. If the adjustment opens up there will be a tic sound, If I hear that the valves will be adjusted. There is a harmonic on most engines that starts when the one cylinder is not on the same power level as the rest, on a lot of trucks it will shake the mirrors. Not like a square tire but fuzz like mirage.If there are no indicators I will still get a look every 2-300k, and if it is not +- .001, then it will be. My experience with Cummins and Cat is that the first time is around 100k and the second time is 6-800k.If the mechanic makes an error, it will usually go to clacking in a couple thousand miles, don't run it that way. They start making noise about .028-.033 and sound off good at .038 but my opinion is that settings like that sell new cams.Same with fuel filters, I know that they do not disintregrate in 5 years so the worst of them will stay togather soaking in fuel for 3 years. I know the symptoms of a plugged filter. So it is on the extended maint list. The air filter has a tattle on it - 10 in of restriction on it and we get a new one. The Isuzu does not have a tattle or a turbo but it smokes, when it increases the opacity it gets a new air filter. Book on it says 30k but it seldom gets 1/2 that.If you are going to do a valve adjust, the first thing is - don't put any dirt in the engine. Wash the top and keep all the stuff clean. Use a newspaper to set the rocker covers on if the bench is not clean and then wipe the gasket with a rag with clean oil on it to collect the dust.There are two ways to count valves to set. Read the book and set to TDC and do the patternOr if one valve on a cylinder is half down the other can be set. I put magnets on all rockers and pick them off as the rocker is checked/set. Takes about 1 1/2 turns to get a full set on the valves and encourages barring slow because it only turns about 1/3rd turn at a time.keydl