How can I make it quiet and smooth as a Cadillac?

[erikz 28]

Obviously dynamat, lizardskin, or other types of coatings would help but what else can I do to make the interior quiet as possible? Do you guys think installing a wall between the trunk and interior would help? You know right behind the rear seat. I know a lot of BMW's and Lexus' is completely sealed between the trunk and interior. How can I make it quiet as a Cadillac without excessively adding a lot of weight? What are your tips and tricks?



I know there are tons of threads about sound insulation, but what are some odd ball things that can help tremendously?

[formula]

well, step one would be sealing up all the little holes etc. in the cabin. Then, make sure all of your seals are just impeccable.

At the end of the day, though, you still are going to have to use a ton of insulation, etc. to even get close. You have to think, luxury cars are designed from the ground up to be quiet and smooth. Old muscle cars...aren't.

[Vegas69]

Can't be done.....

[erikz 28]

Can't be done.....

Sure it can. I plan on running electric cutouts so I can actually have a conversation while driving. You probably can't do it with your motor and exhaust setup.

[Vegas69]

They just weren't engineered to be as quiet. You can probably come close. Getting rid of all the wind noise will be tough. You will need to insulate the roof, doors, firewall, floor, etc very well to come close and pay special attention to window seals and super quiet exhaust.

[formula]

well ok, theoretically it can be done, but you're going to end up spending a very large amount of time and money on this if you really want to do it. there are no "quick fixes"--if there were, everybody'd do it and GM wouldn't spend millions of dollars on it.

other ideas--
obviously thicker carpet--thickest you can buy.
acoustic foam inside all of the empty body cavities.
rubber bushings throughout.
Thicker window glass.
door panel insulation.
bushings on fuel lines (if you're using an electric pump)
bushings on exhaust hangers
pretty much, if it oscillates in any way, or connects to anything that oscillates in any way, it needs to be damped. This includes low-level oscillations like panel resonances, etc.

[parsonsj]

Todd's right: it can't be done.

60's muscle cars have far higher coefficients of drag (drag coefficient or Cd). That means higher wind noise, and it can't be fixed unless you modify the body shape to look like a late model car. And then... you don't have a muscle car any more.

You can do a lot, as posters above have noted. It will cost you several hundred pounds in weight, and dozens of horsepower to wring every last drop of "quiet" out of that 40+ year old car.

jp

[John Wright]

What kind of car are we talking about?...never saw where the OP stated.

I agree with the other guys though, a 40 year old car isn't going to be as quiet as a new Caddy.....those babies are designed with cabin quietness in mind.

[erikz 28]

It's for a 69' Camaro.

Okay, I should have said "closest" I can get to a Cadillac and not "as" a Cadillac. Even if I can get close to a Ranger or another late model car that would be okay. Just trying to give you guys a general idea of what I am trying to achieve. Obviously 40 year old style and technology will never (hmm... maybe sometimes) be a match to today's modern car.

Todd's right: it can't be done.

60's muscle cars have far higher coefficients of drag (drag coefficient or Cd). That means higher wind noise, and it can't be fixed unless you modify the body shape to look like a late model car. And then... you don't have a muscle car any more.

You can do a lot, as posters above have noted. It will cost you several hundred pounds in weight, and dozens of horsepower to wring every last drop of "quiet" out of that 40+ year old car.

jp

There are many newer cars that have a higher drag coefficient than a 69' Camaro that are much quieter. I am willing to lose some horsepower for comfort and daily driving practicality. I will eventually have to weigh how much loss is acceptable. I want to enjoy driving my car more than thinking about how many tenths of a second I lose in an autocross event or drag strip. Im not building a track car here.

well ok, theoretically it can be done, but you're going to end up spending a very large amount of time and money on this if you really want to do it. there are no "quick fixes"--if there were, everybody'd do it and GM wouldn't spend millions of dollars on it.

other ideas--
obviously thicker carpet--thickest you can buy.
acoustic foam inside all of the empty body cavities.
rubber bushings throughout.
Thicker window glass.
door panel insulation.
bushings on fuel lines (if you're using an electric pump)
bushings on exhaust hangers
pretty much, if it oscillates in any way, or connects to anything that oscillates in any way, it needs to be damped. This includes low-level oscillations like panel resonances, etc.

Those are some good suggestions. What's with all the negativity here? Why can't we just have more comments like this?

Also what is pro-touring all about? I don't hear people saying these cars can't handle like today's Corvette? You know what I mean? Im just looking for modern techniques and parts for an old car.

The thing is that I have had a C5 and a Viper GTS, and honestly, I liked the Corvette better. Why you may ask, because I actually liked driving it around. The Corvette is so much more driver friendly. The Viper stayed in the garage more than any other car I have ever had. They both handled well and were both fast, but the Corvette has much more than that. Don't get me wrong, a Viper is a cool car, but I want a car that I like driving in ALL situations.

Are my expectations too high?Maybe I shouldn't have picked a 1969 Camaro.

[parsonsj]

It's for a 69' Camaro.

Okay, I should have said "closest" I can get to a Cadillac and not "as" a Cadillac. Even if I can get close to a Ranger or another late model car that would be okay. Just trying to give you guys a general idea of what I am trying to achieve. Obviously 40 year old style and technology will never (hmm... maybe sometimes) be a match to today's modern car.

That's more like it. Now you've set yourself a reasonable goal, and some of the suggestions above can make a big difference. The biggest obstacle is the exhaust. You'll need to plan the whole car around your muffler setup. Have a look at Andrew Borodin's GTO (in the project area) and how he did his exhaust. His GTO is very quiet, but still has excellent performance.

Let me know, and I can fix your thread title.

jp

[erikz 28]

That's more like it. Now you've set yourself a reasonable goal, and some of the suggestions above can make a big difference. The biggest obstacle is the exhaust. You'll need to plan the whole car around your muffler setup. Have a look at Andrew Borodin's GTO (in the project area) and how he did his exhaust. His GTO is very quiet, but still has excellent performance.

Let me know, and I can fix your thread title.

jp

You don't have to fix the thread title. Alright, so more emphasis on the exhaust. Anyone here have a electric cutout setup that I can see? What kind padding do you guys suggest for under the carpet? Has anyone here seen the foam type padding in Mercedes and BMW's? Where can I get that?

[formula]

the foam they blow into the body cavities or the foam under the carpets?

[erikz 28]

the foam they blow into the body cavities or the foam under the carpets?

The foam under the carpets. It's part of the carpet if I remember correctly. Correct me if I am wrong but I don't think the foam in the cavities on a 69' Camaro would be such a good idea.

[formula]

The foam under the carpets. It's part of the carpet if I remember correctly. Correct me if I am wrong but I don't think the foam in the cavities on a 69' Camaro would be such a good idea.

depends on how intense of a car you're building--if you're stripping things all the way down, pulling the rear quarters like some of the rust bucket-turned-awesome builds around here, you could probably plan ahead to treat the inside of unused cavities with sound deadener and then fill them with the sound foam they use....

[cheapthrillz]

Wow, this is why I love pro-touring.com! You are at completely the other end of the pro-touring spectrum than me. I tend to disregard the creature comfort parts of the car (may be why I like the streetfighter side) because I enjoy the "feel" and "sounds" of driving (although I hate a damn squeak). Sound deadening tends to add a good bit of weight to a car, but to achieve the level of "soundlessness" that you are looking for, you will be giving up a TON of performance....

Not even thinking of wind and drag noise, I would start at the tires and work my way up through the car, to your person.

Quiet tread pattern with softer rubber
Smaller wheels with more sidewall tire to absorb bumps
No poly/aluminum bushings anywhere (strictly rubber)
Steering system needs to be highly dampened
Very soft shocks and lower spring rate springs
Rubber motor mounts
Rubber trans mount
Rubber body mounts
Rubber exhaust mounts for the hangers
.................
.................
.................

Do I need to keep going?

It just seems like most of these things are the things that we try to correct on our cars because they lead to all around "sloppiness" of the car's handling.

I know that I'm not being very helpful, but you have just presented a very difficult question and situation.

[parsonsj]

I enjoy the "feel" and "sounds" of driving (although I hate a damn squeak). Sound deadening tends to add a good bit of weight to a car, but to achieve the level of "soundlessness" that you are looking for, you will be giving up a TON of performance....

Well put. I'm no fan of loud exhaust, but the rest of the NVH is part and parcel of a high performance car, and especially a 40 year old performance car.

[nekkidhillbilly]

id say you could get it as quiet as a modern truck though

[erikz 28]

Wow, this is why I love pro-touring.com! You are at completely the other end of the pro-touring spectrum than me. I tend to disregard the creature comfort parts of the car (may be why I like the streetfighter side) because I enjoy the "feel" and "sounds" of driving (although I hate a damn squeak). Sound deadening tends to add a good bit of weight to a car, but to achieve the level of "soundlessness" that you are looking for, you will be giving up a TON of performance....

Not even thinking of wind and drag noise, I would start at the tires and work my way up through the car, to your person.

Quiet tread pattern with softer rubber
Smaller wheels with more sidewall tire to absorb bumps
No poly/aluminum bushings anywhere (strictly rubber)
Steering system needs to be highly dampened
Very soft shocks and lower spring rate springs
Rubber motor mounts
Rubber trans mount
Rubber body mounts
Rubber exhaust mounts for the hangers
.................
.................
.................

Do I need to keep going?

It just seems like most of these things are the things that we try to correct on our cars because they lead to all around "sloppiness" of the car's handling.

I know that I'm not being very helpful, but you have just presented a very difficult question and situation.

A lot of those are great ideas. It sucks that they affect performance directly. I was thinking more on the lines of interior mods to quiet the inside. I too love the sound of a muscle car. There is none like it. That's why I want an electric cut-out.

id say you could get it as quiet as a modern truck though

Interior sound in a modern truck is not bad. I would be happy with that.

Does anyone here think the wall between the trunk and interior is a good idea? What are some options as far as stuff under the carpet (besides dynamat or coatings)?

[Bryce]

the wall between the trunk and rear seat is a good safety idea. It seperates the fuel tank. NHRA requires a isolator plate made from 0.032" aluminum or 0.020" steel.

[nekkidhillbilly]

just deaden the trunk would be better than a wall