Do you believe it would be enough to retard my timing? I Installed AS&M headers and a Random Tech dual cat y-pipe. It hits intermittently on the passenger side subframe. The section of the y-pipe that is rubbing is from the header on the driver's side after it passes the oil pan and turns to enter the cat. There is only 1/8" of clearance from the pipe to the frame. The section of the subframe that hits is where the the A-arm mounts. Sorry it is hard to explain. Yes I have a LT4 KM.

 

Yes, that will easily cause false knock retard. You could slightly dent the area of the y-pipe where it is coming in contact with the subframe or grind on the subframe area if there is a enough spare metal there. (I.E. not weakening the integrity of the A-arm mount or anything else.)

 

Yeah, any banging and the engine will pick up knock retard. If you don't want to bend the underbody of your car, you could try the fix several guys with FLP's have tried. They used heater hose and placed it between the y-pipe and body to soften the banging.

 

I can't dent the y-pipe because there is a flexible joint where it is hitting. I may be stuck with the FLP fix, won't the heater hose burn?