The 04 GTO started doing this today. We're unsure what it's coming from... lifters, springs, rods, bearings??? It does this at idle and when rpms increase it gets faster. Warm or cold, doesn't matter. The car is in a parking lot and trying to figure it out to determine if we can fix it there or not.

Stock internal LS1, 55k miles. Camshaft: 232/236 FTI Custom Camshaft. .600 lift. Heads: Z06 #243 casting. These have the lightweight sodium-filled valves. Professionally installed Patriot Dual valvesprings.

Video: http://www.youtube.com/watch?v=H0xdm6Md5y4

Thanks!

 

Interesting - that's a strange one but pull the valve covers and see what's going on before you run it any more.

 

spun cam bearing?

 

is that a collapsed lifter? How many miles since your cam mod?