My truck sat for a week, and when I got it back it had developed a loud whistle that comes on abruptly at about 9psi. Not a metal sound - definitely a whistle - much, much louder than the normal whistle of the turbo. If I keep my foot into it, I get's louder and then shifts pitch up. Acceleration seems fine. Stock engine except for a Smarty on a reasonable setting. Could there be a leak in the intake?

Peter

 

It could be a leak on the CAC connectors. The hot side loosen up often til you tighten them several times and then they will stay tight. Also a hole in a rubber connector. It doesn't take much of a hole to loose a bunch of boost and make noise. You have to check the connector very closely. I've had a hole on the bottom side that was hard to feel or see. Craig

 

A little off topic here, but do you have any pictures of the 68' w/ the Cummins in it? I'd really like to see that.

You didn't remove your silencer ring did you?