Why'd they change the valve clearance specs?

[WMoroni]

Why were the valve clearance specs changed for the 07 5. 9s vs say the 05 and older ones. When we put in my pdr cam we set them to the 07 specand didn't give it much thought. I'm pulling my injectors out this week (one bad one for sure, checking the rest, going back with 50hp DDP nozzels) and will naturally be readjusting valve clearance while there. My question is what setting to go back with? The older spec or the new spec. Why was it changed? Different valves or was it emisions related? Any benifit to one setting over the other? Thanks

 

[ENafziger]

What exactly are the specs you're talking about?

I think Don recommends about 0. 010" and 0. 020" for the Helix 2, aftermarket cams.

--Eric

 

[JWadford]

What exactly are the specs you're talking about?



I think Don recommends about 0. 010" and 0. 020" for the Helix 2, aftermarket cams.



--Eric

i use this spec also, i have run . 015 on the ex side with no problems and . 008 on the intakes

 

[cerberusiam]

The specs were changed to accomodate the changes in the valve compositions in the later engines. The valve seats and valves themselves are made of a different material that is reacting differently to the heat generated by the emissions engines. The lash was increased to accomodate the extra flexibility the vlaves have with respect to EGT's.

 

[Tinman]

I set mine to what the sticker on the engine read. . 010 and . 026

 

[CKelley1]

i guess i get to reset mine,

 

[WMoroni]

I'm going back with what the sticker says.