My 70 has a 454 with 3 inch exhaust, edelbrock mufflers and 3 inch tailpipes that turn down before the rear bumper. The interior noise level is just too much for more than a 20 minute drive. What have you guys/girls done to deal with this? Has anyone used the sound deadening product that looks like carpet padding covered in foil? Should I modify my tailpipes so they stick out past the rear bumper so sound does not reverberate under the car? Thanks.
Make my car quieter
Bill70
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My 70 has a 454 with 3 inch exhaust, edelbrock mufflers and 3 inch tailpipes that turn down before the rear bumper. The interior noise level is just too much for more than a 20 minute drive. What have you guys/girls done to deal with this? Has anyone used the sound deadening product that looks like carpet padding covered in foil? Should I modify my tailpipes so they stick out past the rear bumper so sound does not reverberate under the car? Thanks.
BILL, I HAVE 3" PIPES AND I KNOW WHAT YOU MEAN. THAT FOIL LIKE INSULATION LOOKED SUSPCIOUSLY LIKE HOUSE STUFF SO I BOUGHT 2 4'X20' ROLLS AT HOME DEPOT FOR $20 EACH. I HAD ENOUGH TO OVERLAP AT THE HUMP, WALL TO WALL BETWEEN THE FIREWALL AND REAR DECK, AND BACK THE KICK/DOOR PANELS. IS IT QUIETER? MAYBE A LITTLE. THE FLOOR DOES'NT GET AS HOT, CRAWL UNDER THE CAR AND YOU CAN SEE ALL THE HOLES THE FOIL COVERS UP. YOU MIGHT "QUIET IT DOWN" WITH AN H PIPE. THEY DON'T REALLY QUIET IT BUT BUT MAKE THE EXHAUST LESS PULSEY. DYNOMAXX MUFFLERS I'VE HEARD ARE THE QUIETEST AT IDLE BUT A FULL THROTTLE ARE JUST AS LOUD AS FLOWMASTERS. 3" EXHAUST IS LOUD NO MATTER WHAT.
STAY COOL.
STAY COOL.
Straight exit pipes should help alot. John E is right- 3" is going to be loud no matter what. I had turn downs on my 72 Elky and I have straight exit tips on my 72 Malibu. The difference is night and day, even with the Malibu possibly having double the horsies.
The same shop did both systems for me and explained that the resonance off the ground is what makes the turn down systems so loud.
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Later,
Rob
1BADS72
The same shop did both systems for me and explained that the resonance off the ground is what makes the turn down systems so loud.
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Later,
Rob
1BADS72
Bill,
Check out the article in Popular Hot Rodding Jan. 99. It is quite detailed. I plan to use their system on my 70 454 this spring. I to do not like a lot of noise, and this system seems to fit the bill. Let me know what you actually use to correct yours.
Mherb7592@aol.com
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[This message has been edited by Mike H (edited 01-16-99).]
Check out the article in Popular Hot Rodding Jan. 99. It is quite detailed. I plan to use their system on my 70 454 this spring. I to do not like a lot of noise, and this system seems to fit the bill. Let me know what you actually use to correct yours.
Mherb7592@aol.com
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[This message has been edited by Mike H (edited 01-16-99).]
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4,703 Posts
Bill, I had headers with 3" headpipes back to two-chamber Flowmasters,then dumping down in front of the rearend on my 468" 68 El Camino. The noise and resonance was unbearable. After suffering with it for a few months, I took off the dumps and had full-length 2.5" tailpipes installed, kicking downward at the rear bumper.This made a huge improvement but it's still pretty loud. Next step will probably be a crossover. High-HP big blocks will always be hard to quiet down. A 2.5" mandrel-bent system would probably be liveable and might be my final step.
Bill..objective articles I've read don't recommed 3" unless racing /450+ HP. I have never heard the Edelbrock mufflers so I have nothing to compare them to. My 70 has a mild 454 and the exhaust is a Flowmaster 2.5" with 2-chamber mufflers with SS style chrome tips. It has a raunchy sounding idle and WOT isn't bad either. But with 37's at the rear at 2000 rpm there is quite an exhaust droan inside the car. But I'll leave it 'cause at 10 mpg I don't make to many trips.
If the sound really bugs you try this:
1. leave the front 3" pipes as is.
2. consider Walker Hemi's/Super Turbos or
Flowmaster 3-chambers.
3. Install manadrel bent 2.5" tailpipes and straight exit tips.( I've read where there is better scavanging with 2.5's)
This might be the least expensive way to go, and if you can install the stuff yourself all the better.. My .02's...keep us posted.
Dave M
Aces 1818
70 Malibu BB
If the sound really bugs you try this:
1. leave the front 3" pipes as is.
2. consider Walker Hemi's/Super Turbos or
Flowmaster 3-chambers.
3. Install manadrel bent 2.5" tailpipes and straight exit tips.( I've read where there is better scavanging with 2.5's)
This might be the least expensive way to go, and if you can install the stuff yourself all the better.. My .02's...keep us posted.
Dave M
Aces 1818
70 Malibu BB
Thanks for all the replies. I have added a crossover pipe. It has lowered the frequency of the sound but it's not any quieter. I really want to cut the tailpipes where they turn down and add some extensions so they go beyond the rear bumper. With the car idling I kneeled down in front of the rear wheel and listened and it was so loud it sounded like I had no tailpipes on it. I do not want to run 2.5" tailpipes because the engine is making a lot of power. If I do anything else I will try the super turbo mufflers. As I make progress I will let you all know. Thanks.
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3,453 Posts
The Only good noise reducing stuff I have used is called DYNAMAT. They sell it at car stero places to soundproof cars for better stereo listening. You heat it and apply it to the floors, inside the doors and quarters, behind the rear seat, and you can even put it on the roof under the headliner. This stuff really absorbs sound but it is also really expensive.
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