the importance of running overhead adjustments on deisel engines

That will vary depending on the engine in the truck. Generally you can find a spec for each in the recommended service intervals.

 

Unfortunately I don’t have that information. I have a 60 series 14L. And if I may ask what is an average price for this service. Thank you in advance

 

Every 100k after the initial, try to find one reputable place and have them always do it, preferably have the same competent dude do it. If it's done right when you get it back there's zero engine vibration anymore at idle, MPG increased by close to 1 mpg, power is more noticeable. The valve system is the mechanical clock works of the engine, ECM can make fuel air adjustments for a bad mechanical clock but ECM can't adjust the valves, have to get regular overhead adjustment mechanically aligned

 

~$450 at the freightliner dealership

 

Im going to do this on a new volvo,manual says initial at 150k miles and next after 300k,should cost 650$

 

Just got quoted $900 for 6 hrs labor on a D13 with no engine brake from the Volvo dealer. Seems excessive to me.

 

I just recently got a valve adjustment on a d13 with the new common rail. First trip logged 11k miles and mpg increased by 1 mpg almost. Went from 5.9-6.3 to 6.9-7.2 and thats 80k @70 mph 3.08 rears 22.5 lp. Also tq curve feels much healthier, takes much longer before i need to start downshifting.

 

I did the 500k overhead interval on my dd15 ant it restored power and in gained 1mpg.Ill get it did again at 700k.