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exhaust rattle?

F

fatboyreyn

Guest
I have a very annoying rattle when I first start my 86 in the morning. I sounds like a bolt bouncing around in the exhaust system. I have had the complete exhaust off twice, and cannot find anything loose. My question is about the two resonators on the front y pipe. are these converters or just resonators? Is it possible they are cracked and making the heat shield rattle? By the way when the car is warmed up, the rattle completely dissapears. This is driving me nuts:mad
I have stock manifolds with the egr port plugged, air tubes plugged, stock y pipe, new cat, and stock rear y pipe into freeflow magnaflow muffs. the exhaust also pitter-patters sometimes, I think you call it resonating, while your driving. Should I punt stock exhaust and go with long tube headers? I like the car a little loud. but don't like the resonating. I am 99% sure the rattle is the exhaust, as opposed to the flywheel or something. by the way the engines runs strong, so I doubt it is internal. Any ideas. guys. thanks for listening.
 

vetteboy86

Well-known member
Joined
May 26, 2003
Messages
2,760
Location
IN
Corvette
1986 Black "Indy 500 Pace car replica"
Those are converters on your front y pipe. I doubt you have a cracked heat shield because it would rattle regardless of heat.

I experience your problem with the dynomax mufflers I used to have, only they would rattle when the temps were below or at 50 or so, then once the car warmed up it went away. Not sure what it is in the mufflers.
 

jmccloud

Well-known member
Joined
Feb 1, 2003
Messages
694
Location
Maryland
Corvette
1995 White Coupe LT-1 Auto
Exhaust rattle

I've had 3 cars with cracked converters (fortunately not the Corvette). They sounded like a bolt rolling around in the exhaust - just as you describe. Only one of them eventually plugged up (poor high rev. performance and screwed up vacuum so speed control and A/C vent control went south) but the noise was really irritating. When I removed the really bad converter, some of the honey-comb interior fell out in ragged pieces.
If your noise quits, I'd wait for worse.
Good luck.
 
F

fatboyreyn

Guest
I found the rattle, thanks to imccloud. I pulled the y pipe off again and found BOTH front converters were completely crumbled up like big rocks rumbling around. cut both off, cleaned them out 100% , welded them back on, put it back together, and SHAZZAM, car sounds great. No more pitter-patter from exhaust pipe. No rattle at all. Lesson learned. When I had them off before I probably banged them around and started the crumbling process. Oh well, another problem solved! I love the challenge of these beasts!!!!!! thanks for all your input dudes.
 

G Winter

Well-known member
Joined
Aug 21, 2004
Messages
2,177
Location
NW Iowa
Corvette
1990 red convert 6 sp
They do that with heat cycles, and age.
You now have all three cats cleaned out? What are you running for mufflers and how loud is it. All my cats are still in working order and I tried eliminating the mufflers and on longer drives I couldn't take the resonence. Had to put the mufflers back on.

Glenn
:w
 
F

fatboyreyn

Guest
I still have the main cat, after the y-pipe, which is brand new. Needed that one for inspection. I am running dynomax free-flow mufflers, but I cut them open and added,believe it or not, about 6 inches of baffle from my Harley stock mufflers. I tried the freeflow mufflers, which have no baffeling inside at all, and like you, could not take the resonance. Mine sounds real close to what I want. I still have a tiny bit of resonance, depending on where the gas pedal is. I just ordered 4 resonance tips for the back and I hope these will make the car sound perfect. You can't beat the sound though, when you stomp on it. Excellent!
 

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