Engine noise?!

[FastAndFurious]

The car is 89 3.2 MTX with stage 1 cam.

The noise happens around 2-2.5k rpm under heavy load(going uphill or giving 1/3 gas when rpm is around 2k). The noise is kind of like metal scratching noise (it's hard to describe), and it goes away quickly. Weird thing is it's easy to hear some days, and other days it's hard to hear the noise. I believe it happens in all gears, but it's especially easy to hear in 2nd and 3rd gears. (The noise has been there for a while I believe. Not sure how long it has been there for sure tho)

It's hard to pinpoint where the noise is coming from since when the car is idling, the noise doesn't happen. It kind of sounds like it's coming from front of the engine, but I'm not sure.

I was thinking of rod bearings, but they were supposedly changed about 10-20k miles ago, and I haven't really lugged the engine. What could it be? One of the pulleys?

 

[sperold]

Cam chain tensioner?
Take your hood off; and get someone in the passenger seat to help narrow it down.

 

[AREA 91]

Take off the accessory belts, and run it.
This will eliminate an accessory.

 

[FastAndFurious]

I think I found the culprit!

I was thinking maybe it's butterflies flapping(metal scratching/tapping noise. I forgot to describe the noise as tapping. oops...). I disconnected the vacuum hose for the secondaries and drove about 40 miles today. No noise at all anymore!

I guess I don't have to worry about it anymore. Thank god..

 

[rubydist]

so that suggests that the vacuum canister for the secondaries is leaking - you want to fix that and not just leave the vacuum hose off the secondaries because then they are always open and that hurts low speed torque and mileage.

 

[FastAndFurious]

I will look into that. I plugged the vacuum hose back.

I thought some SHO engines have flapping butterflies, and there is no way to really fix the issue and it's not a big deal (My old 91 also had noisy butterflies). Correct me if I'm wrong.