Is it normal for the engine to make an "extra sound" around 6k rpm? Does something in the engine change, open, or close at this point of the engine's speed? When I get right around there this added sound sounds something like scraping or rattling. Anyone?

 

I think the 3rd set of injectors open around 6750..
or I might be wrong about the 6750 figure.. maybe it is lower/closer to 6k
which might explain it.
Anyone ?

-B

 

That sounds about right.

 

You sure its not the Rotary-Ping sound you are hearing? It sounds like marbles in a coffee can. What grade of gas do you use?