My specs are in my sig below. I drive my car with the top down 99% of the time, so the only time I hear this noise is when the top is up. It sounds just like valve chatter/rattle from running low octane fuel. I only run 93 octane. I have been running this build for over two years, so if something was going to fail it would have by now. I had stock LS2 heads for a while, now I have ported LSA heads. The block or heads have never been shaved/decked. Pushrods were stock at one point, they are now 7.425 Manleys. I am running a -12cc Mahle piston, so with the LS2 heads 64cc chambers I was around 10.5:1. Now with the LSA heads 68cc chambers, I am around 10.0:1. It has always had this noise and it doesn't change. It is under load in a tall gear (slight acceleration going up a hill in 5th gear or accelerating to pass on the interstate in 6th gear). I can hear my blow off valve so I can gradually increase throttle position until I hear the blow off valve close. At that point the noise stops. I used to have the stock Procharger blow off valve, now it is a Tial Q.
It seems like a long while ago, I changed something in the tune and it moved the noise to a little higher in the rpms (like the noise started at say 1500 rpm, and after it started at 2000 rpm) but, for the life of me, I don't remember what changed it. At the time I was chasing something else that was more important than the noise. I have reduced timing in the areas where it happens until the car won't hardly run, with no affect. Is there any way it could be the injectors making the noise? This could maybe explain why it quits the instant there is boost, with the increased fuel from PE and the subsequent increase in IPW (see pics). I'm at a loss. Hopefully someone has run into this before. Any help is appreciated.
no boost.JPGboost.JPG