5000 mile break in??

[FlyinGN]

I have a 2001 2500hd with the 6.0 and it always felt quick but not 300 hp quick. It has 1700 miles on it.. My friend who has one felt the same way. He said his old 5.3 felt just as fast. Then on day that all changed. At the 5000 mile mark the truck picked up drastically. He was wondererig what happened. Took it to his GM dealer and they told him this..

That GM has 2 seperate programs in the PCM's. One for up to 5000 miles and a new one for after 5000 miles. The one before 5000 is the 'breakin' period and the timing, fuel curve is adjusted so the engine is cut back 'about' 50 hp. After the 5000 mark its a full 300 hp.. ??!! WHAT? It sounds like it could be done.. Any truth to this?

 

Frank

[RyanbabZ71]

I dont know about that.  I cant imagine just driving down the street and you hit the 5000 mile mark and get improved performance.  I can say that over time my 5.3 has seemed to get stronger.  

[MarkD]

I can say that over time my 5.3 has seemed to get stronger.  

 

Ditto!

[GreenRado]

Double ditto!!

 

I suppose that's entirely possible, but I'd be very surprised if GM has actually gone to that trouble, especially in light of some of the self-inflicted problems they have w/ some components.  

 

My gut feeling is the "GM dealer" was blowing smoke . . .  

[Guest]

Sounds like the dealer people gave you a warm glass of spiced BS... No way thats true... I have reset my ecm by pulling fuses... Same thing the LS1 guys do... And I definately didnt lose any power...