What's this sound?

Hey all,

I posted here a while ago asking about engine troubles and rod knock.. well that drama is still ongoing.

I brought the car to my normal shop and they of course couldn't replicate the sound there. Said they drove it for an hour and there was no sound. Cleaned the MAF and it pulls just fine.

Well I get it back, drive it for two days and my sound returns - with a vengance: cold start, warmed up, clutch in or clutch out. The only time I don't hear it is after the 3k rpm range, but that could be due to the exhaust drowning it out. There's no check engine lights, oil pressure is good, no flakes or shavings in the oil (changed it when all this started) and nothing to indicate any health issues with the car other than this horrible noise. I've taken it out a few times to keep the battery in good shape but it's pretty loud and embarrassing.

Anyway here's an under the car and inside the car shot, I'd suggest using headphones.

Im posting this here before I bite the bullet and take it to a dealership. If anyone has experienced this before I'd rather get the lowdown before I pay their exorbitant diagnosis fees. Any ideas?

Can't help you, but it will help others if you list the year and any mods done to the engine and drive-train.

Ah yeah:

1997 4.6 bored .20 over back in 05. 20k miles on the rebuild, 103k on the block. Shop did the rebuild.
MAC CAI
MAC 5/8 longtubes
BBK catted H pipe
4.10 gears
Rebuilt T45 in 2009 probably 6k miles on it
Stage 2 clutch
Aluminum driveshaft
MSD coilpacks

Nothing outrageous just bolt ons mostly, I don't know what the hell I am doing beyond that, especially not on the 32v.

So it doesn't change with the clutch depressed? It almost sounds like the clutch fork is about to fall off.

No change that I noticed.

Catalytic converter.
Try shaking the exhaust system to hear if it rattles

That's what I thought but I just changed the H-pipe August of last year. It's got less than 100 miles on it. I suppose it's possible since BBK has been known to have quality issues with their cats. I'll try shaking it and report back.

Standing by.

It doesn't make any noise, but I can't exactly shake it hard either. It's pretty sandwiched between the mufflers and the headers so there's not much give to shake with.

Time to get a mechanic's stethoscope. Probe everything from the cats to the heads, and even the block.

It could be a piston wrist pin, or a broken cat. It's hard to really tell with the video alone.

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As bad as that sounds, it doesn't sound catastrophic to me. Sounds like something is loose somewhere

Revvv said:

Time to get a mechanic's stethoscope. Probe everything from the cats to the heads, and even the block.

It could be a piston wrist pin, or a broken cat. It's hard to really tell with the video alone.

Sent from my SM-G930V using the svtperformance.com mobile app

Click to expand...

Yup, you are going to have do some digging.

Mine had a sound like that. My issue was the passenger side of the upr x pipe was hitting the k member. I knew it was close when I installed it but I figured with urethane motor mounts the motor wouldn't shake much. The motor wasn't the issue but I didn't consider the unibody flex. Ultimately had to massage the pipe with a mallet a little bit to clear it up.

Sorry for the delay in response. I have next Tuesday off so I'll do some digging and report back on what I find.