DrDyno

Hi All,

Recently, I installed a set of Allen Stainless chambered muffler eliminators on my '96 LT1. Link is here:
http://forums.corvetteforum.com/c4-g...ps-w-pics.html

I loved the sound from outside the car but, lately, the resonance (some call it Droan) at around 1700 RPM has become bothersome. Researching the forums, I found a thread in the C6 section on noise insulation that offered a neat solution. A link to Page-6 of that thread and the answer I was looking for, Post #115, by "Presidentialpawn" is here:
http://forums.corvetteforum.com/c6-c...t-drone-6.html

By drilling a 1/2" hole in each exhaust runner and welding a short pipe between them (what the muffler folks call an "H" pipe), the sound bouncing between the two apparently changes the frequency of the noise coming out of the tail pipes. That change in frequency has a direct effect on the resonance in the cockpit.

Some pics are following but first let me say the effect was remarkable. The cockpit at 1700 RPM is now quiet enough to easily hear the radio; the resonance I now have has moved up the RPM scale to about 2800 RPM (about 90 MPH on the road); and, the sound, even when loud, is much easier on my ears... "softer" than it was. It was well worth the $40.00 I spent at my local muffler shop!

HlhnEast

Shoulda gone ahead and open the holes up. An H pipe helps balance the exhaust and makes it flow better. Never noted a lessened drone but I usually did this with a completely new exhaust so I never had the before and after. Makes sense tho.

Nice write up and pics!

1993C4LT1

Awesome, thanks for sharing this

DrDyno

I used 1/2" holes because the thread I referenced and the poster of post-115, "Presidentialpawn," said you could use almost any sized pipe but NOT to make the holes bigger than 1/2."

Being unfamiliar with "H" pipes, I just followed his instructions. When I suggested 1/2" holes to my muffler guy (who's had decades of experience), he seemed to concur without further recommendation. But, I, too, wondered if bigger holes would have yielded even better results.

GKK

The Corvette catalogs sell a rear Y-Pipe with the crossover tube welded in but, many people have said, it didn't lessen the resonance.

It's probably because as you've mentioned, the holes have to be no larger than 1/2"...