For the past 2-3 weeks, my car has been making this real bad/strange engine noise.

It sounds like a helicopter, but has a faster rythm/tempo to it.

When I was getting $$ from the ATM a few nights ago, I left the car running (GF inside) and it was real profound. When I changed my oil a few weeks ago, I didn't notice anything under the car that was loose or different because I thought it might be a loose belt (I recently changed). The car still runs strong, but from a dead stop under load, it sounds slightly louder underneath the car.

Sometimes the car makes this noise and sometimes is doesn't, but it seems to be doing it a lot more lately. Do you think it's a bad case of piston slap or maybe a bad lifter or a bent pushrod? Any help is appreciated.

 

Do you know what an exhaust leak sounds like? It could be that. I'm having that problem right now.. just getting the funds together for my headers to do away with it.

 

I think that could be it. Possibly from where my y-pipe meets my headers because that's where it sounds like this noise is coming from.