Now that NovaJane is staying with me, I decided to address one of my pet peeves (and also a brand spanking new legal issue): Noise! The car is (was) Loud! Essentially, the exhaust consists of race car style 2.25-inch primary tube headers that bolt into a 4-inch collector. From there, each side goes into a 4-inch into a 3-inch slip on reducer and then into a 3-inch exhaust system. The system is made up of a Hooker "X" style cross over and then into a set of 3-inch in and 3-inch out Hooker VR series mufflers (straight through with glass packing). Finally, it exits into 3-inch turndowns in front of the rear axle.
I had the exhaust pretty much nailed down when I moved from the west coast to the prairies. By the time I had the car finished, the province I live in established a new set of noise laws: Cars, light trucks and motorcycles must not be over 101.3 decibels. If the vehicle is below 103.3, you get by with a warning (all tests are on the L-Max scale from idle to 3,750 RPM). Over that dB number, it's a fail and you must fix it. There are several parameters that include where the test equipment is located in relation to the exhaust exit, along with others.
So I decided to test my car:
L-max was 104.7. Fail! Oops...L-O-L
Now what? I could add tailpipes, but they foul both the electric fuel pump and the home brewed ARB I made for the car. Can't use them. I decided to try a set of dB killing cone inserts in the exhaust. The holes in the cones have more surface area (combined) than the diameter of the pipe. There is very little exhaust restriction.
These cones can go almost anywhere, but they're most effective if they're close to the collector.
So I installed mine in the reducers. The pointy end must face forward. Once installed, each cone was tacked in place (you can actually bolt them in as well).
Next up, my research pointed to using a set of resonators. My dilemma is the straight sections in the cross over aren't very long. Additionally, the exhaust runs very close to the big M-W aluminum driveshaft. That means the resonator body has to be short and relatively small in terms of diameter. So I came up with these straight through 3-inch in, 3-inch out, 4-inch body stainless jobs from Vibrant Performance:
I sliced open the exhaust and had a local shop TIG weld the resonators in place. This is the complete "new" system, less mufflers:
In order to tighten up the exhaust during the install, I used a ratchet strap hooked to the exhaust and anchored under the car to the front suspension cross member. Worked slick. Then I used a bottle jack to raise it up (it fits tight up under the car):
Once the mufflers were reinstalled, it was time to test it. I used the same parameters as the "before" test. The results were excellent! The cones and resonators work, without adding a whole bunch of restriction to the exhaust:
If I get stopped and sent to a test station, I'll remove the fan belt. Reason is, big block Novas with long water pumps have no room for a clutch fan. The direct drive fan is quite noisy. I figure running it less fan will should get me down to the legal limit...Worst case scenario is I will get by with a warning...
