I am considering doing a true dual exhaust conversion on my '77 4-speed. I have used the search function and done considerable research.
I am only interested in better sound, not looking for more power, in fact
I'm worried that too much reduced back pressure may decrease my torquey power curve that I enjoy now. Almost everyone who has done this reports a greatly improved sound. Every kit I have seen includes a high performance, "turbo" type muffler or they fabricated their own pipes and used a Magnaflow, Flowmaster, Borla or some other "premium" muffler ! My question is simply how much of this improved sound is coming from the true duals and how much from the upgraded mufflers ?? Did they start with stock or quiet mufflers ?? I have already gone through 3 different mufflers on my car and am currently running Gorlich Accelerators which appear to be identical to 2 chamber Flowmasters without a cat. I think my car sounds very good and is just about right on the "loudness". The $500 question is will it sound better with the true conversion using the same mufflers ??

P.S. I have seen where many add an X or H pipe thus eliminating the true duals to add power or get the sound just right ???

 

Has anyone gone true dual and kept the same mufflers?

 

I have done several conversions using stock 2.5 inch manifolds with 2.5 inch pipes from allens ss exhaust they will make them with regular or turbo mufflers but exhaust mods will not make up for the low compression motors from that era have not seen much difference in performance only the sound.
Mark

 

Thank-you for your reply but the original post stated that I was not interested in power only a possible change in sound quality!

 

I wouldn't worry about an old wives' tale affecting your torque.

 

For what its worth, I'm of the opinion that true dual exhaust results in a sound that is too loud and obnoxious, more like two four bangers than a V8. Adding the crossover between the two pipes makes for a much more mellow sound.

 

Hmmmmmm, srry drwet..... I disagree !!
Changed my exhaust to true dual with Magnaflow muffs and its nice and throaty when you want it....but not obnoxious at all....
But....that's just my fiddy cents...

 

I think that I have the answer you are looking for. I have a 78 L-82 4 speed that had a completely stock exhaust system when I began making changes starting in 1983.

The first change was the elimination in 1983 of the stock cat with a "test" pipe in that location. In 1989, I replaced the mufflers only retaining the all of the rest of the OEM Y pipe exhaust with Monza Turbo mufflers which I still have today which gave the car a louder smoother more European type of sound, not the traditional "motorboat" muffler sound. In 2003, I replaced all the OEM pipes-the head pipes and the rear 2.5 inch Y pipe-with 2.5 inch true duals from midamerica using the OEM cast iron manifolds but used the same Monza Turbo mufflers that had been on the car since 1989. The sound got much louder with the 2.5 dual pipes which I completely expected.

Why? Really a simple answer that involves basic physics. The OEM 2.5 inch Y pipe system is 2 2.5 inch pipes from the cast iron ram horn manifolds to 1 2.5 inch pipe under the passenger compartment and then splits into a 2.5 Y pipe before going to the mufflers. That system is VERY restrictive, MORE so with the OEM cat. It essentially is a single 2.5 inch exhaust since the exhaust flow is determined by the 1 single 2.5 inch pipe under the passenger compartment-the point of greatest restriction and the limiting factor in the exhaust flow. Switching to 2 2.5 inch true duals actually increases the exhaust flow by the square of the diameter of the original single 2.5 inch pipe in the OEM system-another words, the exhaust flow does not go up by a factor of 2 with 2.5 inch duals but by 4X !-the 2.5 inch duals theoretically flow 4 times more air, thus being much more efficient, making more sound with the same mufflers, and more power. Hope that helps!

 

What can I say? To each his own. Switching to true duals will definitely make the car louder and you may like the sound. The reason is that with true duals the frequency of the exhaust is lower. It really is like two four bangers. Adding a balance tube or crossover between the two pipes effectively doubles the frequency of the sound coming from both pipes, making for a mellower tone. You may wish to try the true duals, and add the balance pipe if you don't like the sound.

 

True duals change the sound to a lower frequency because now you have two 4 cylinder motors.

So you get a deeper tone.

The other factor is pipe diameter. bigger 3 inch system have a very deep tone. I have 3 inch pipes and 3 1/2 inch in and out race mufflers

 

True duals will increase torque across the entire RPM range. Restrictive exhaust reduces power at all rpm even on a stock engine.

 

I just did this conversion earlier in the year. My power went up across my full RPM band. I have long tube s/s headers with an x-pipe on 2.5" pipes. All s/s. Magnaflows.

I posted pics in a similar post a few minutes ago.

 

I thought the purpose of going with the X or H pipe was to mellow out the sound and change the tone.

Going from the current 2 1-2 setup to a true dual exhaust sounds like it will help in both areas. More power, better sound. Win Win.

kdf

 

Now we're getting some answers!

 

One correction: The OEM front head pipe system is actually 2 2 inch pipes that converge into 1 2.5 inch pipe under the passenger compartment through the cat and splits into 2 2.5 inch pipes for the L-82 cars.