Resonator

[Brian]

Opinion time:

I understand the resonator for '57 is required for concourse, but what does it do for the car?

What are the pro's and con's of keeping it or leaving it off?

I intend to put on a stainless exhuast, so I save quite a few dollars if I leave it off.

Second question: has any one used the new stainless shield that Casco is selling to reduce floorboard heat from the muffler? My floor was always hot before, and I was going to put some shielding material under the carpet, but this looks interesting.

 

[nomadbird]

Brian,
I'm afraid you're opening up a hornets nest where there will be such widely diverging opinions, no one will know what is the right choice. I will start with your second question about the heat baffle for the muffler first. No, I haven't used that particular item but yes, we have used that principle for many years out here. There is some improvement but there is so much more to be done that you wonder if it's worth the effort. Example: The left exhaust manifold and exhaust pipe is about 2" from that rubber piece around the steering column. That is a horrible source of heat transfer into the cockpit. Second example: I'm constantly burning my right leg on the gear selector lever. What can be done about that? You see, it just goes on and on. My opinion is that this is like bringing ice cubes to a camp fire to keep cool.

Main issue: Resonators. There will be varied opinions on this too. Exhaust sound is very subjectve. The only thing that sounds good and "right" to me on a 312 is a stock carbon steel system with resonators. I have one car with carbon mufflers and resonators using stainless pipes. After driving that car for an hour, the difference in the coefficient of thermal expansion between the carbon steel and the stainless steel must be great enough to cause exhaust leaks at the joints. Big mistake. Wish I hadn't done that. A 312 without resonators will sound raspy and will bark back on down hill deceleration. It is not considered a viable option here where we have a lot of hilly terrain.

Stainless mufflers are usually made from thinner gage material to facilitate fabrication. They are accepted in CTCI Concours but sound crappy. Not as bad as a Chevy 350, but still nothing near "purty".

Final analysis--- Complete carbon systems sound the most authentic and sound nicest. BUT-- they do have the shortest life. I have two cars with complete carbon systems that are 10+ years old. Still no rot or perforation.
The stainless system will probably last anyone a lifetime.
To me, old cars appeal to at least four of the five senses. Sound is one of the senses that I like to satisfy.

Tom D.

 

[Brian]

Tom - I like the hotly contested debate: it gets the blood flowing, and allows you to talk passionately about what you love.

After driving that car for an hour, the difference in the coefficient of thermal expansion between the carbon steel and the stainless steel must be great enough to cause exhaust leaks at the joints. Big mistake.

I assume you mean whatever you do, don't mix the two?

 

[nomadbird]

Brian,
The worst leak is on the left side between the stainless exhaust pipe and the carbon steel muffler. It is quiet when it's cold, and leaks after it gets hot. Can't say I've noticed much leakage between the carbon mufflers and stainless tail pipes. I used the stainless on this so-called "driver" to avoid surface rust formation. Another "driver" that has carbon steel pipes looks just as good.

Thought I noticed someone selling Aluminized systems. That seems like a happy compromise incorporating the nice sound of carbon steel and approaching the longevity of stainless steel. That is what I would try. Of course, your environment in Cleveland is a lot more humid throughout the day than it is here on the coast. Maybe stainless steel is your only realistic option. Regardless of location and climate; short running time is death to these old carbon steel exhaust systems. If the engine can't be run long enough to get hot enough to evaporate the condensation in the exhaust system, it will self-destruct.

Tom D.

 

[Brian]

Casco is selling the aluminized systems.

You are right about the rust factor in cleveland, and the minimal driving of the car: I'm worried about that condensation as well.

My main concern was how different the system would sound with or without the resonator. Of course Clevelands flat, cold, and usually wet.

 

[nomadbird]

Brian,
I started to send you a smart aleck private message about crossing the Ohio border without resonators, but decided it sounded too prejudicial. Just don't do it O.K. I'm just going to summarize my opinion by saying: Get the aluminized system with the resonators, always run the engine long enough to evaporate the condensation in the exhaust system, and enjoy it for 8-10 years and then do it all over again. Like I said earlier, I have a couple cars that have the complete carbon steel system that are somewhere between 10-14 years old. They are never started to just move them from the garage to the driveway or vice-versa. They are always driven an absolute minimum of 13 miles every time the engines are started. In Cleveland, I'm sure 20 miles would probably do the trick.

Tom D.

Edit: Invariably, people who have complete stainless systems will ask why the carbon system sounds so much better. I'm not sure. But knowlegeable owners can tell the difference in the sound.

 

[earlybirdlover]

I guess I'll throw in my .02 worth. I have a complete stainless steel exhaust with resonators on my 57. I think it sounds good but there is a subtle difference in the sound vs a carbon steel system. The one thing you don't want to do is to mix materials as Tom D. has found out. Stainless steel grows MUCH MORE than carbon steel when heated. It also seems to retain heat more and that might contribute to your problem of interior heat. I don't know if the inside of the "aluminized" exhaust is coated but that is where all the corrosion happens. If the coating is only on the outside it seems to me that it would be a waste. It may look pretty on the outside but it's still being eaten from the inside out. Good luck with your decision. Jim

 

[Brian]

I'll ask that "inside alumizied" question next week.

Jim - you feel that your stainless steel set up retains more heat?

And I do intend to drive this car around! Fact is, I just can't wait: when will it ever be done!

 

[earlybirdlover]

Brian, I think that the stainless retains more heat therefore its surface temp. is higher when the engine is running. No scientific data to back this up, just my observation. I have had stainless exhaust on my 1960 Corvette for almost 20 years and on my T-Bird for 1 year. Both still look brand new and I will never have to worry about exhaust problems again. On both systems the mufflers (and resonators on the T-Bird) are made from very thick material. At least as thick if not thicker than the original equpiment. Take care, Jim

 

[Winston]

resonator

Brian, your original question, What does the resonator do? I'm not 100% sure but maybe someone knows. I think it may be twofold. First, for a more sporty sound. Remember they were trying to compete with the corvette. And second, possibly adds to a certain amount of back pressure that the engeneers may have been looking for. Just a guess

 

[Brian]

That's what I'm really trying to understand, Winston!

What is it really for?

That is, what are the ramifications of leaving it off?

That is, (other than concourse violations) what will be pro's and cons?