POLL: C3 True Dual Exhaust

[mvftw]

Right, Cats started everywhere in '75, but smog motors started earlier, including low compression stated in '71. '70 was the Last real muscle year!

 

[SHADY80]

sounds"reeeeeeeal"nice

put the mid-american tru-duels, straight back;with FLOMASTER 40;s; and i;ll be honest with ya all,it sounds extra exellent.By the way "NO CATS"

 

[cesully]

For all you "true" duallies and the folks with the smog stuff removed---- Does your car have a strong exhaust smell to it?
I have a new 1978 S/A with the smog equip removed and I'm thinking about true duals, however, when I start my car it has a strong "gassy" smell to it-- The wife complains about how it stinks up the garage and stays there even after I have pulled it outside--can't say I blame her either.
I assume this is because it is an old car and I experience this at car shows so I would assume this is the nature of the car due to its age. Do I have a problem with the carb...?

do you experience this also- is it normal in other words...

thanks for your responses,

Sully

 

[JLMvette73]

Anyone tried out one of the mufflerless chambered systems that are available?

 

[DakotaFlash]

Half true...'74 had duals and smog. Smog started everywhere in '71 and just got worse...

My '74 NEVER had any smog stuff on it. No pumps, no holes in the exhaust manifolds, nothing. Clean as a midyear.

 

[78SilvAnniv]

Oh yeah, Baby!

Anyone tried out one of the mufflerless chambered systems that are available?

I purchased a used set of ss MidAmerica chambered from a CAC member last fall.
Freezing cold outside after the installation but I drove around with the windows down and a HUGE grin on my face!
Now my GM crate engine sounds like a BB when it idles! When I step on the go pedal, she ROARS!
Husband and I can still have a conversation while driving, but you can definitely hear the exhaust rumble. Any acceleration makes me smile. My mpg has suffered because I like to listen to it accelerate.

As for the exhaust smell...sometimes that can be a fuel smell from the evaporative canister not working correctly, but if it is an exhaust smell...that can occur with a new exhaust system.
My chambered did not have that smell because it was used when I purchased it and had already worked its way through that.
Perhaps there is an exhaust leak?
Running rich?
Timing issue?
Heidi

 

[JLMvette73]

Re: Oh yeah, Baby!

I purchased a used set of ss MidAmerica chambered from a CAC member last fall.
Freezing cold outside after the installation but I drove around with the windows down and a HUGE grin on my face!
Now my GM crate engine sounds like a BB when it idles! When I step on the go pedal, she ROARS!
Husband and I can still have a conversation while driving, but you can definitely hear the exhaust rumble. Any acceleration makes me smile. My mpg has suffered because I like to listen to it accelerate.

As for the exhaust smell...sometimes that can be a fuel smell from the evaporative canister not working correctly, but if it is an exhaust smell...that can occur with a new exhaust system.
My chambered did not have that smell because it was used when I purchased it and had already worked its way through that.
Perhaps there is an exhaust leak?
Running rich?
Timing issue?
Heidi

How good was the fit up on your car? I've seen several of these installed where it appears that the pipes hang down too far just before they make the slight bend upwards in front of the rear axle, rather than being tucked up against the floor.

Jerry

 

[78SilvAnniv]

Had a 'vette shop install it

It does appear that the pipes hang down further than my stock system, but these pipes are MUCH bigger than my stock ones were.

I've measured my clearance, and at my lowest point on the passenger side exhaust pipe near the rear of the tranny it is 3.25 inches.

Overall, I am very pleased with the system. I've read posts from several members who have gone to chambered and one did the install himself and said it was a piece of cake...the hardest thing was chopping up the original exhaust to get it out of there.
If you are concerned about it fitting well, you could have a shop put some additional bends in them to make a closer fit, but I think mine fits just fine.
Heidi

 

[ironmoo]

?

I have true dual exhaust now with cats.

Thanks for the info LEEJANDZ, I was thinking about doing the same on mine here in Calif. Last two smogs checks the visual inspection was in the engine compartment with not a peek underneath to look at the pipes or cat. I do wish to go dual cats into true dual pipes.
Question is on the '82, there is a sensor going into the cat. Wonder if I go duel cats, I will need to accomidate the second cat to have a similar sensor and patch it into the first...or perhaps have a cross bar before the cats to equalize the exhaust eeadings.
Any ideas anyone?

 

[Copdogcorvettes]

Well you need to check your states laws tobe sure you can do it first. It all depends on what you are doing it for; Sound-- cost savings of replacement--etc. My 78 had the duels and Targa mufflers. It sounded great and looked good to. The 400sb flowed nice through the 2 1/2 inch pipes. I just changed it all out with Hooker 4inch side pipes. Just love the way it looks and sounds. It all comes down to what YOU like.

Gary

 

[JJS]

'71 is the last true "muscle" year

I always thought '71 was the last year of "true" dual exhaust (no smog/catalytic). It also marked the last year of "muscle," since
high horse LT-1's and LS5's were still available. HP dropped significantly in '72.

 

[Robin7TFour]

my 1974 has true duals from the factory. no cats required:s :s

 

[Blue82]

IRONMOO, the sensor on the 82 is the O2 sensor. If you go dual you should move it up to the header and probably should install one in each header so you can monitor both sides of the motor. I have seen mods for this so you'll have to look around.

Also, if you stay with the current setup, you might want to mod the sensor to a heated O2. it works much better that way because it is located so far back from the flame path that it has a hard time keeping the proper temp.

 

[MaineShark]

If you go dual you should move it up to the header and probably should install one in each header so you can monitor both sides of the motor. I have seen mods for this so you'll have to look around.

You can wire one side to the computer, and the other to a air-fuel ratio gauge in the cockpit - the two sides will be very similar, unless your car has some major malfunction.

Also, if you stay with the current setup, you might want to mod the sensor to a heated O2. it works much better that way because it is located so far back from the flame path that it has a hard time keeping the proper temp.

Absolutely do like the man says... A non-heated sensor won't get a correct reading at the collector.

Joe

 

[DakotaFlash]

"True Muscle"

Also have to remember that the way they figured HP ratings changed as well. You suffer a 50 hp drop in the LT1 from 70 to 71. 370 hp in 70, 330 in 71. What's the compression ratio on the 71 LT? Was 11 to 1 on the 70. You might also want to quantify your assertion about muscle. I, like many other enthusiasts have modified our engines to make plenty of muscle. Take for instance my 74 at 480hp and 501 ft/lbs. And the neat thing is that you can open my hood and not notice any of the things that make it that way. No nitrous cheating, no big high rise intakes, etc. If you know how to build em, you can keep a very stock look and have a real sleeper. Incidently, I started out with an 70 LT1 engine to arrive at the power I have now. Maybe give it a try !

 

[venom94558]

Depends on the year

I would say it would depend on the year of the car. I live in Illinios and every year I have to take my 78 vette for Emissions test. I would not pass with out the cats, at least I don't believe so. I have them on with dual flows, I think it sounds great.

 

[KANE]

Running duals with an 02 sensor is fairly simple. I use only one O2 sensor and its on the right side of the exhaust system. I am running ram horns on it with the side pipes, so the sensor is located just after the manifold.

I have had O2 sensors in my 78 with TPI since 1997. When I ran full length headers (before my sidepipes), I placed the bung in the collector can. It still gets plenty hot there.

Word to the wise- take the time to really think about where you place the sensor. Think about accessability versus road debris damage and running wires in less than ideal places. You get to be the engineer here, so you may as well place it somwhere good!

 

[cowboyra]

I installed a set of Hooker Headers, dumped the Cats and installed stock turbo mufflers on my 75 L-82 as part of an "Enhanced Airflow" effort -- Sounds great and puts out a few more Hp at the same time.

 

[pauld]

I was thinking about installing true duals on my '81 and now that I am reaing this thread, I have made up my mind to definately get them!!! people say that I can expect a 30hp increase once they are installed, can't wait

 

[Dave L.]

Pauld - putting the Mid-America dual kit on my car was one of the very 1st things I did when I got my car....money well spent!!

Dave