Did I hurt my Cobra?

[31BCobra]

Okay so for anyone not following my build thread, I did a Fore level 2 fuel system, and upped the boost on my 2.3l Whipple to ~24-25psi. Whipple said it should be okay for the redline I was at, so I went for it. Car performed well on the dyno and aside from a squeaky belt on cold starts the car runs really well.

Today I started her up and I hear this knocking noise at low RPM. The noise became more pronounced as the car warmed up and is noticeable at idle and low rpm, but goes away as the rpm raises. The sound seems to be coming from around the Whipple mostly, but I am not 100% sure on that. Used a screwdriver to try and find the source but as far as I can tell everything sounds normal.

Here is a video. https://www.youtube.com/watch?v=11EAeVa_ZbY

 

[Blueline]

Pull the blower belt and see if it still makes the noise. If it does a compression test should be your next shot. GL

 

[Bdubbs]

It almost sounds like a bad belt tensioner.

 

[Brutal Metal]

It almost sounds like a bad belt tensioner.

Or even an idler pulley bearing, the sound gets louder as he moves to the front of the Whipple?

 

[31BCobra]

Or even an idler pulley bearing, the sound gets louder as he moves to the front of the Whipple?

Yea, the sound does seem a little louder near the front of the blower. I just can't pinpoint it because all the other noise kinda overwhelms it in the engine bay. I am going to try running the car with the belt off to see if that is the issue.

 

[Bdubbs]

Or even an idler pulley bearing, the sound gets louder as he moves to the front of the Whipple?

Yeah, I've had both go bad and make that similar sound. I'm thinking either belt tensioner or the idler right next to it. But taking the belt off will help determine.

If noise isn't there with belt off, then take off tensioner and some idlers and spin the pulleys by hand. A bad one will have more resistance and gravel feel.

 

[31BCobra]

Okay so I took the belt off and while doing that I realized the bearing on the tensioner let go. Damn thing wiggles all over the place. Started her up without the belt just to be sure, super quiet. Never realized how much noise the blower contributes to under the hood noise. So I guess I will wait until Christmas or black Friday to see if I can get a good deal on one of the Thumprrr tensioners. Thanks for the help guys.

 

[Blueline]

Congrats on the easy fix!!!

 

[Brutal Metal]

Yeah ramping up 25lbs of boost is gonna reek havoc on the oem tensioner. For the time being I'd throw a new stocker on til you can upgrade...

 

[01cobravortech]

Great thread OP. One of the strangest sounds I ever heard on these motors and they do make a lot of hard to pin point sounds. Thanks for updating. Many don't do the same. And great job on the video and sound quality buddy.

And good job on the diagnosis Bdubbs!