My old mufflers (generics from a chain shop I believe from whoever had it before me) were really starting to rot out so I decided to have some fun and learned some interesting things...

car is stock L48 1977, factory manifolds and converter in place. I am planning on a true dual kit in the near future, perhaps the chambered pipe version..so what the heck, sounds like a good time to experiment a little bit.

cut off both mufflers and went to just turn downs in the back of the car..made up some hangers to support the whole deal. The result? It's still not that loud! There is some resonance from 1200-2000rpm that isn't really all that unpleasant for a weekend cruiser. No doubt this is from exiting UNDER the car and not out the back. It's no louder that the edelbrock setup on my friend's camaro with an lt1 swap in it. He also runs a high flow cat.

So why no real noise? I'm going to guess a super restrictive factory exhaust setup especially that stock converter! Idle mixture needed to be enrichened. As an added bonus my temps dropped 5 or 10 degrees. It's been an interesting experiment The guys here at work think it sounds nice and throaty outside the car..interesting. I used the turn downs with the idea it would cancel some of the higher pitched noise and it seems to have done that.

-Matt

 

If I think clearly (My 74 has always had actual duals) your going 2 into 1 into 2 for the Cat. If the cat is as old as the rest of the system, it may be plugged. Get rid of it and go complete duals. I have the Chambers, I love them - very tolerable at idle - obnoxious when you stand on it. I wouldn't have it any other way.

 

great! thanks for the input on the chambered setup!

My neighbors are very tolerant as they all have loud cars too (mostly old and rusty trucks *grin*)

Yes I am stock 2-1-2 setup and pretty sure the converter is old and plugged. The new setup will of course fix that...uh...problem.

 

My dad and I were on a trip recently in his '87 Suburban. Had some problems - obviously exhaust restriction. No power going uphill... etc. Pulled over to a little mechanic in a little town in CO. He cut the muffler off, thinking that since the cat was relatively new, it was not the likely culprit. With the muffler cut off, there was absolutely no difference in volume. Cut the cat off, and it really roared!

Ben

 

It is amazing how much the cats can keep the volume down on your car. My car sounds so much better now than it did when I had the 2-1-2 system on it. I truly think ridding of the cat was the biggest contributer to it sounding better.

 

The factory cat is the biggest HP robber on the car.

I posted a picture in another thread of the Mad True Duals setup I bought. Looks great! I should have it on in the next week or so.

-Mark.

 

If you are ever going to put on headers now is the time to do it, before you get your exhaust put on. If you want to hear something awesome do what I did - remove the exhaust yourself from the exhaust manifolds all the way back. Install your headers and drive to the exaust shop like that!

 

Yes, the converter quietens it. Just removing mufflers works for some who have to run converters. Have mentioned it several times on the forum, there are several, C4 in particular runing w/o mufflers.
If you want info., you might want to see what many refer to as my Exhaust topic.
http://www.corvettefaq.com/c3/ganeyexhaust.htm

 

I'm sure the turn downs help a lot. I'm running duals, crossover pipe, and Flowmaster DeltaFlow 40's with turn downs directing the exhaust below and past the rear bumper. I don't find it to be very loud at all. Other members on the forum have found that the DeltaFlow 40's are too loud. I wonder if they have turndowns directing the exhaust out past the rear bumper.

 

I just put headers and dual exhaust with Magnaflow mufflers on my 77. With the cat out of the system and the engine re-tuned the car has a large gain in performance

The through flow Magnaflows sound great.

I have flanges at the header joint, aft of the cross frame and at each muffler so I can remove sections to work around the transmission and differential.

 

I'm thinking of doing the exact same exhaust setup... What size pipes are u running and would you change anything? Are they shorty or long tube headers?

 

The pipes are 2 1/2" and the headers are long tube. I wouldn't change anything.

 

Having a new exhaust installed today. 2 1/2" from headers back in aluminum with a set of magnaflow wideopen stainless with a set of dual turndown tips.

I've had 2" pipe and $19 mufflers on my car for yrs and am very interested how much better it runs and sounds with this new setup.

 

I've got an 81 that I put headers on,dynomax muflers and then turned out 3" slash cut tips in front of the rear wheels.

Not near the amount of noise I was expecting, definate gains in performance.