Johnny,

This coming Monday I plan to drop my exhaust and gut the cans. I look forward to hearing yours. What exactly did you do? Did you have resonators in the tips? Do you have any inprogress pics or did it look like the "exhaust gutting" post?

Thanks, Dave # 3463

Johnny,

thaks for the reply. I look forward to hearing it as well as your comments on how the sound is different from stock.

thanks again,

John

Dave,

If you go back to the beginning of this topic and click on the Gallery button you will see all the picture with captions.

I will upload the sound here on Monday.


Johnny

I did a slightly different modification to a set of GTS mufflers. They actually are pretty quiet. On a supercharged 4.6, they flow pretty good and make power where we let off at 7000 rpm on the dyno with no drop. Would like to try this same modification to mufflers on a cleveland to test. Anyone want to send me a set of mufflers?

Dave,

What did you do different? Did you add a secondary input similar to what Fred Terry did on his 5S and have them flow straight thru? I'm interested, so please tell me more. Mine are off the car and ready to be shipped out.

John
johnmaffeo1@yahoo.com

Johnny in England,

I was asking about the gutting of STOCK 1972 Pre L exhaust mufflers. I have studied the posts mentioned and reviewed the pictures and understand the concept. The articles discuss GTS exhaust. My question is pretaining to stock exhaust. Anyone have any thoughts or direct experience regarding stock exhaust with resonators in the tips?

Thanks, Dave # 3463

John, my modification is hard to explain. all I did was cut some holes in various places. With a good high resoultion pic of the inside of a muffler, I could mark out what I did. I was a dumb a$$ for not taking pictures. I really didnt remove much but opened up some passages to try and make the dampening chambers work without restriction. I will try and describe.

The two baffle plates have an area with about 8 3/8 holes on each side. I cut out these 3 areas in a circle to make about a 2 inch hole in each side of each baffle. Two front and one rear. The second rear baffle area I cut a half moon hole. This was in hopes of prevent resonance between the two tips by change the tuning frequency on each side of the muffler. These cuts will help air flow out better from between the baffles.

The second modification involves cutting two 1 by 2 inch slots in the perferated pipe on the inlet. Between the two baffles I cut one of these rectangular holes on each side. These holes should reduce the back pressure wave from reflecting back up the inlet from the end of the muffler and allow additional flow.

On the 4,6 this modified muffler was amazingly quiet.

I have GTS exhaust on my 74. At 2200 rpm..the car resonates with a boom, and sets off car alarms all over the place..I can't imagine a system with no baffles...got to be VERY loud..and maybe illegal in the state of california.

I installed the gutted, or rather bypassed exhaust cans on my mate Geoff's car this weekend. It sounds fantastic. Huge improvement over the original GTS cans, but not too loud. I think the resonators in the tail pipes must do something because there is not much holy pipe left inside the cans with my Y piece installed.

We took the car out for a drive and found it to be no noisier inside the car at all. In fact Geoff said that the uncomfortable resonating drone at 1800RPM (427 Windsor) had been reduced considerably.

I did take some video clips with my camera, but failed to really capture the sound. I wanted to stand behind the car and record Geoff accelerating away under full power, but the bloody roads around Surrey (just outside London) are so busy, we couldn't find a quiet road anywhere.
I found that rather frustrating coming from sleepy old Devon where the roads are quiet and I can drive around like Mad Max..most of the time.

I dont know how to upload video clips, so I am going to send them to Garth and ask him to upload them. He's better at this than me. One of the video clips is my car (351C) accelerating away on an air field. My exhausts are factory group 3 so almost identical to the modified cans on Geoff's car (red GT5) I manage to change from 1st to 4th but it still sounds great!

To summarise: If you do the same as I have in this story, it will sound great. Not as loud as you might think.

Johnny

Johnny,
What size pipe did you use for the modification???


Ron