I recently added a 2# upper pulley with stock belt to my lightning and also the Predator Pulley Tune. I had the Lightning dyno'd and all appeared well with 11.5-11.7 AF and 372 RWHP and 452 RWTQ. A few days after I started to notice a rattle noise from top of the engine when either I rev the engine in park or when I am cruising down the road. It appears worse at around 2500 rpm and greater. The noise does not happen at WOT, so probably it is why I did not notice it on the dyno. Is this detonation ??? Any ideas would be greatly appreciated.

 

Cavitation... do a search, nothing to worry about.
Have your chip or tune raised a 100 rpm, noise will go away.

 

Thanks for the info. So how would the 100 rpm increase stop the noise higher in the rev range. I am a newbie to this and am Just curious

 

Did a search. Got the answers. Thanks

 

RPM increase made no difference at all. The rattling which is almost like a diesel noise only happens when the throttle is almost closed, foot off throttle and at the point of gear change (basically off load). Does not matter what RPM, but is more noticable and in 3rd at constant 40-50mph. Does not do it at toe in or WOT. I also adjusted the A/F and added more fuel and it appeared worse. Would a custom predator program cure this???

All you Guru's out there PLEASE HELP!!!!!!!!!

 

I get that kind of rattle only when 3+k rpm when I'm about to shift into another gear, right when the clutch engages I hear that kind of rattling.

 

You should get a custom tune. I have only heard bad things about the ones that come on the predator.

 

Bad gas????

Try some octane boost or alchohol to remove water????

When you say with engine in park it really eliminates the detonation in my mind.

Piston slap, Cam chain tensioner stuck???

Best of Luck.