have had this problem since I did my big bang upgrade 1.5 years ago (new engine and complete new exhaust). I have SLP 1.625 headers, 3" hi-flo cat and 3" single in/out flowmaster w/ a magnaflow muffler.

The problem is that when I apply throttle above ~3K+ RPMs a noise comes out my muffler that sounds like a machine gun, bag of marbles, fart pipe sound. It sounds like crap. I finally heard it from outside when the alignment shop guy took it for a spin. I don't have any audible exhaust leaks and my exhaust system isn't rubbing on anything. I swapped my original flowmaster for the magnaflow thinking the flowmaster had welds broken inside which caused the fluttering sound. Didn't fix it. The piercing sound is coming out from the muffler and has a distictive snappy sound.

I plugged of the lines going to the air tubes and cat. No change in the sound.

I sounds like the old style lowrider cars. Sort of a zapping sound. I can rev it in my driveway and it makes the sound. But if you rev it slower, not blipping the throttle, it doesn't make the sound. It does in on acceleration. but if you keep the RPM (lighten up on the load) then it goes away.

Any ideas?

What make the old style low-riders make that sound?

 

Glasspacks

 

James , James, OLD STYLE LOWRIDER, NAH Bro. It's called OLD SCHOOL. and like Mikey said that was the glasspacks installed backwards. I've heard your car a couple of times and it sounds O.K. Try Borla, see how that sounds. Let me know how that sounds. I love the gutted cat sound, but I want to be a sleeper. One thing I've noticed is that mudstains don't like to play no more and I'm getting bored.

 

I was gonna say Fromaster but... hmm.
Its just the muffler, IMO. Try a different one. I like Dynomax mufflers in particular.

 

I swapped fom the blowmaster to this magnaflow. The sound occured with the blowmaster as well.

I do have a couple clamp only connections. The one by the SLP cat adaptor is particularly a little lager the the tube being inserted into it. Would fresh air being introduced to the hot gases cause this? I'm running out of things to investigate.


pic of my muffler

 

What cam are you running?

 

ZZ4, straight up.

 

Actually the "Old School" lowrider guys install something like 1" diameter tips coming off the muffler. The restriction causes the "popcorn" sound.