Echoing Sound from Exhaust

[Guest]

I installed a new exhaust system on my 73 Limited and now it has an echoing sound around 50 MPH or anytime you press the pedal down more than @20 percent. The old system was quiet (until it backfired one day and blew a hole in the muffler) and it did not have a resonator.<P>I bought the system from Kepich and got a $60 Walker muffler from an auto parts store. The muffler should be good. Also I just replaced the exhaust system on my 88 Town Car from the same place and it is silent. Also, the system on the Lincoln bolted in nicely for just $118.00.<P>I read the prior posts about Kepich and they were right about fit. I had to cut the pipe between the Y pipe and the muffler because it was to long and put in a sleeve. Also, I had to get an expander in order for the tailpipe and the wrap-around the axle pipe to join. Finally I had to take it to Midas so they could weld the sleeve. I would have bought the exhaust system for my 73 from the same auto parts store but they did not carry the pipe between the Y and the muffler - nobody in town did. <P>Any ideas on how to get rid of the echoing sound? ??? Thanks

[rocketraider]

First- what series Walker did you get? They were/are a GM OEM supplier, but an aftermarket universal type muffler will usually not be as quiet as OEM. <P>Did you put the resonator on? <P>Combination of the above will often cause a booming noise in exhaust, or at least it did on my 1976 Olds Regency after I had a custom dual system sans resonators put on (I actually don't mind it-gives the old beast a little attitude).<P>Last- the OEM wye and headpipes on most all GM cars in that era were a pipe-within-a-pipe design that quietened them down a lot. I doubt any aftermarket supplier does that.

[Guest]

Sounds like (no pun intended) like you got a "turbo" design. They have that hollow bellowing sound that resinates through the car. They are very common replacment mufflers.

[Guest]

The muffler was number 21848. It is the same number that is on the Walkerexhaust.com website. So, I would assume it is the correct muffler for the car - paid $60 so it's not the $25 cheap-o muffler. Still can't understand why this one on the Buick is loud and the Lincoln is not.

[rocketraider]

Well- the Buick is a 455. The Town Car is what, a 302 with a catalytic converter? Lotta difference in the size of these cars' balls...<P>The piping isn't hitting the underbody anywhere? Is the Kepich piping physically larger than OEM? What you're hearing is resonance and/or a harmonic frequency that is there all the time, just shows up more when you hit certain RPM ranges and exhaust flows. If the noise is unbearable, try installing a resonator. If that doesn't solve it, you may need to hunt for an NOS GM muffler.

[Guest]

In the past I have had problems with muffler shops forcing the pipes into line, consequently they do not hang free and are in a constant state of stress. <P>Exhaust systems are supposed to be hung from the car with hangers to support the weight, if everything is not hanging free sound can be transmitted to the chassis resulting in a kind of thrumming sound like you describe.<P>Try giving the exhaust system a wiggle to make sure it's hanging free, if it's too tight sound will be transmitted. I once had a 84 Bronco that had so much stress on the exhaust that it split the Y pipe at the weld because the installer was too lazy to bend the pipe another 5 degrees to make everything fit freely. I had a buzzing/thrumming noise in the cab but had attributed it to the exhaust coming out in front of the rear tire instead of the factory rear location. <P>Of course this happened long after the warranty was up and a replacement stainless headpipe was $180. I could have choked that guy, now I check my exhaust everytime I have it worked on. After I fixed the headpipe and had everything hanging freely all the noises disappeared.<P>Might be your problem too?<p>[ 02-19-2002: Message edited by: Chuck da Machinist ]