Muffler Replacement
Thread Starter
7th Gear
Joined: Nov 2013
Posts: 7
Likes: 0
From: Orlando Florida
Muffler Replacement
Have gotten a lot of useful info on here so I decided to join.
I just installed a new exhaust system (OEM style, modern cat) on my '78 Pace Car and am concerned with the sound made by the replacement mufflers that came with the kit. At idle they sound good, but right around 1000 rpm they drone so bad that they almost resemble the mufflers that you see on Civics and Subarus.
Is this typical or did I get a bad pair of mufflers?
I just installed a new exhaust system (OEM style, modern cat) on my '78 Pace Car and am concerned with the sound made by the replacement mufflers that came with the kit. At idle they sound good, but right around 1000 rpm they drone so bad that they almost resemble the mufflers that you see on Civics and Subarus.
Is this typical or did I get a bad pair of mufflers?
Burning Brakes
Joined: Jun 2010
Posts: 1,165
Likes: 93
From: Bellmore NY
Welcome aboard.
Ok, so at idle it sounds good, but drones at 1000 rpm? Is this a typo, or is your idle significantly lower than 1000rpm?
Typically most of us would experience drone at some sort of cruising speed/rpm on the highway, like lets say 3k.
I have magnaflows for the time being [about to swap in a set of side pipes]. In general they are fairly quiet, but with the windows up and a consistent cruise speed, I do experience some minor droning.
Any chance of posting a video of what you are experiencing?
Ok, so at idle it sounds good, but drones at 1000 rpm? Is this a typo, or is your idle significantly lower than 1000rpm?
Typically most of us would experience drone at some sort of cruising speed/rpm on the highway, like lets say 3k.
I have magnaflows for the time being [about to swap in a set of side pipes]. In general they are fairly quiet, but with the windows up and a consistent cruise speed, I do experience some minor droning.
Any chance of posting a video of what you are experiencing?
Thread Starter
7th Gear
Joined: Nov 2013
Posts: 7
Likes: 0
From: Orlando Florida
Idle is around 700 or so after the engine has warmed up. Above 1500 or so and at crusing speed this is not an issue. Didn't have this with the factory mufflers and these are supposed to be stock.
I will work on posting a video in the next day or so.......pictures are worth a thousand words.
I will work on posting a video in the next day or so.......pictures are worth a thousand words.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Are you running an auto or a manual? 1000 rpm is well below the stall speed of any automatic transmission that would go behind a 350. If you're running a manual and driving around at 1000 RPM... downshift. :O
Is it that as the engine passes 1000 RPM it briefly makes a lot of ruckus, or are you really cruising at 1000RPM?
Is it that as the engine passes 1000 RPM it briefly makes a lot of ruckus, or are you really cruising at 1000RPM?
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,112
From: Crossville TN
If you verify that you don't have any metal-to-metal contact with any exhaust system components to the frame of the vehicle (except, of course, the connection between engine and downpipe at the exhaust manifolds), then any such noise would be a resonance set up by the sound energy in that exhaust. If the noise is actually eminating from the exhaust components, modifying the system might change the frequency or reduce the noise level. If you have dual exhaust system, perhaps installing an "H" pipe connection between the L and R pipes would be beneficial.
First, make sure that there are rubber isolators at all frame-to-exhaust mounting points on the car. Then, consider simple modifications that might change resonance characteristics. As a last resort, you may have to go to a different muffler to resolve the problem.
First, make sure that there are rubber isolators at all frame-to-exhaust mounting points on the car. Then, consider simple modifications that might change resonance characteristics. As a last resort, you may have to go to a different muffler to resolve the problem.
Thread Starter
7th Gear
Joined: Nov 2013
Posts: 7
Likes: 0
From: Orlando Florida
Thanks.
Single pipe system here. I'll look at the mounting points first. The only place this could be happening is the support just forward of the transmission cross member. At that point the pipe is firmly clamped against the support with no rubber or insulator between the two.
If that doesn't work, I'll search for new, better sounding mufflers.
Single pipe system here. I'll look at the mounting points first. The only place this could be happening is the support just forward of the transmission cross member. At that point the pipe is firmly clamped against the support with no rubber or insulator between the two.
If that doesn't work, I'll search for new, better sounding mufflers.
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Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
I can't help but think your motor is a little mad at you if you're holding it at 1000 RPM in gear with a stick, although I don't think you'd be doing 20mph in first. I try to keep my RPM above 1500 when the clutch is engaged.
Drifting
Joined: May 2012
Posts: 1,353
Likes: 44
From: Calgary Alberta
You likely have the replacement hideaway style mufflers. I also have a set of these on one of my cars and they certainly drone when I'm come up out of first gear into second. Bothered me at first, then I got used to it and overall I like them. The mufflers I have came from Corvette Central. I doubt it is an issue with any clamping points, unless the rubber in the muffler hangers is truly shot.
Thread Starter
7th Gear
Joined: Nov 2013
Posts: 7
Likes: 0
From: Orlando Florida
Thanks all for the good advice.
It appears there were 3 issues upon closer inspection;
1. When the parking brake was disengaged, it gave the brake cable just enought slack to rub the tail pipe. A small dent in the top of the pipe took care of that. (when i fit the exhaust, the brake was engaged and the cable was tight)
2. Added insulators at the solid frame mount and under the pipe where it crosses thru the transmission crossmember
3. And finally, the rear Y pipe had a few holes in it where the 2 pipes were welded together. I will be taking to local shop to get these holes welded shut.......brand new parts and they are junk. Incredible that the vendor let this leave the shop this way.
It appears there were 3 issues upon closer inspection;
1. When the parking brake was disengaged, it gave the brake cable just enought slack to rub the tail pipe. A small dent in the top of the pipe took care of that. (when i fit the exhaust, the brake was engaged and the cable was tight)
2. Added insulators at the solid frame mount and under the pipe where it crosses thru the transmission crossmember
3. And finally, the rear Y pipe had a few holes in it where the 2 pipes were welded together. I will be taking to local shop to get these holes welded shut.......brand new parts and they are junk. Incredible that the vendor let this leave the shop this way.
Racer
Joined: Oct 2013
Posts: 254
Likes: 3
From: Tampa Bay Florida
If you verify that you don't have any metal-to-metal contact with any exhaust system components to the frame of the vehicle, then any such noise would be a resonance set up by the sound energy in that exhaust. If the noise is actually eminating from the exhaust components, modifying the system might change the frequency or reduce the noise level. If you have dual exhaust system, perhaps installing an "H" pipe connection between the L and R pipes would be beneficial.
First, make sure that there are rubber isolators at all frame-to-exhaust mounting points on the car.
First, make sure that there are rubber isolators at all frame-to-exhaust mounting points on the car.