Exhaust valve lash

[Grinder1]

What's the latest on the .026 vs .020 exhaust valve lash discussion? My 07 5.9 calls for the .026, with a range of .015-.030. I would prefer to set the exhaust valves at .020. Is that looser .026 spec just for emissions? Any harm in running with the tighter spec? Would seem logical that it would be ok if Cummins is giving a minimum spec of .015. My buddy's '05 sure seems a bit quieter than my truck, with double the miles on his I might add. I read that Cummins changed to the looser spec in '06.

 

[cerberusiam]

Cummins did not change the spec, Dodge did. The .010 and .020 is Cummins rec.

 

[Grinder1]

Cummins did not change the spec, Dodge did. The .010 and .020 is Cummins rec.

I'm not a big fan of beating the valve train to death via sloppy valve lash. Was that looser spec done to meet tougher emission standards? Why else would Dodge do that? Or were there exhaust valve/seat problems due to heat not being properly transferred with the old .020 spec? I don't mean to go down the emissions trail on this, just wanting to know that no harm would come by running the .020 lash spec this late vintage 5.9

 

[cerberusiam]

Multiple theories why it was done, one makes as much sense as the other. If one is running gauges and using them it is not likely an issue. A stock engine with no gauges and a heavy footed driver MAY see some residual benefit. That is offset by the smoother, quieter running of a tighter lash. As far as that goes, .009 and .018 is fine if monitoring temps and not constantly maxxing loads.