True Dual exhaust

[Feltman]

Looking at installing a true dual exhaust system on my 81. Question...what do you do/or have to do with the air pipe running from the cat....I have searched this forum and found info about cat vs no cats, but nothing on what needs to be modified for a true dual exhaust system..maybe nothing....that is why the question.

 

[Dave L.]

first of all I should mention that my car is emission testing exempt. I have duals with no cats. I removed the long pipe and check valve you are referring to and plugged the divertor valve where it originates with a rubber plug and clamp. I have since removed all emission items from my car altogether. I save all the items I remove from the car in the event I might want to return the car back to stock condition. I've enclosed a picture of my engine compartment. notice the rubber plug on the AIR pipe coming out of the exhaust manifold,this is the type of plug I'm refering to. Your local NAPA dealer has these.

Dave

 

[platato]

Hi Burglar!

Let me ask the same question a little different way. We have a Calif emissions car now located in smog free central Illinois. We want to go catless true dual as well but want to disturb as little of the car as possible. This will be our only noticable variation from the way the factory shipped it.

1. Can I simply use the plug method while leaving everything else
in place i.e. the smog pump etc. still operational?

2. Could I have a fitting welded to the new exhaust pipes to
accept the smog line?

3. Would any of this mess with the computer or anything else?

4. Should I have a cross over pipe and where?

Thanks in advance!

Platato :BOW

 

[Dave L.]

Hi Platato- First of all when you say,'"smog free",I assume you have no sniffer or visual checks of any kind.
1. Yes. This is how I had mine for 2 years after changing over to duals. I removed my AIR pump belt and the pipe as mentioned.I can see no problem leaving the belt in place. You will not get a check engine light.
2. Yes I suppose you could but I see no useful purpose for doing so. The purpose of the pipe going to the convertor is after the engine is warmed up,air is directed to the lower bed of the convertor to provide an oxiding atmosphere for effictive catalyst operation(quoted from my shop manual)hence,I see no need to install the pipe on a true dual set up.
3. No. I went as far as removing ALL emission parts and did not get a check engine condition or any drivability problems. One very important thing is you WILL need an oxygen sensor in one of your exhaust pipes. The Mid-America pipes come with a threaded O2 sensor hole in the left pipe.
4. It's up to you. Mine does not. If you were to install one I would say somewhere forward of the transmission cross support. If you go this route you might want to talk to other 80-82 owners and see where they placed thiers. I have the Mid-America 401 stainless kit on my car.



Have fun!.......Dave

 

[sfakins]

Feltman,

When I went to duel exhaust I had a bunn welded to the driver's header. Just about any muffler shop can do this for you. As for as the cross over pipe, I don't think there is any room prior to the crossmember without the pipes sticking below transmission oil pan level. I don't know the performance effect by placing it behind the transmission crossmember so I just left it off. I would still like a cross over pipe - I heard that it increases performance and Flowmaster highly recommends it for all dual exhaust system. I might contact them or ask on this forum for some technical advice on this subject.

Good Luck,
Steve

 

[aerie1761]

true dual exhaust

First I have classic tags which doesnt require emissions.I bought a set of true exhaust from mid america.They will bolt right up to your exisiting tubular manifold which by the way only came on the 1981 They can be used with stock mufflers or whatever you want. I went a step further and put on a set a chrome hugger headers .Ihave not put it on a dyno but I know my horsepower has increased and the engine can finally breath.What a big difference not only in performance but it really sounds great.

 

[Feltman]

What mufflers are you using..tell me more about the headers..any modifications have to be made? Where did you get them...I want to keep sound close to stock, but with a little more rumble to it.......

 

[Ludigdrums]

I never understand why or how these threads just seem to stop midway!

Anyhow, I'm restarting it....

I have true duals on my 81 as well. Have two Cats with plugs on them. This is how I got the car so I don't know what they are or anything. I also have headers, no crossover pipe.

Speaking of which, what is the crossover pipe, what does it do, and why would you want one. Wouldn't that just mess up backpressure and the whole point of having "true" dual exhaust. The only other reason I can think of is possibly tuning the sound to be the same out of both pipes.

Also, what mufflers do you guys like as Feltman asked!

Thanks!

- Jeremy

 

[DDLS3]

Jeremy,

The crossover pipe on a true dual will enhance the performance slightly as the opposite headers are off cycle just enough to cause some scavenging to occur which pulls the gas out a little faster. It also improves the sound a bunch. Dynomax Super Turbo mufflers and Flowmaster are popular choices for high flow good sounding mufflers.

 

[Ludigdrums]

Crossover Pipe

Sounds good...any pictures of what one looks like?!

- Jeremy

 

[DDLS3]

Jeremy here is a link that will take you to some pics of the balance pipe. There are two versions, one is an X arrangement the other an H



http://store.summitracing.com/defau...bykeyword&searchtype=both&part=xpipe&x=11&y=3