Lil Red - Duramax 6600/Allison 1000 Conversion & OBS/NBS Dash Conversion

[More Power]

As mentioned earlier, I've embarked on a civility program for Lil Red. The first step was to add a foam rubber block (5 x 5 x 24") to the back of the cowl injection hood scoop - on the inside. I theorized that a lot of engine noise was coming through the screened back of the scoop and into the cabin air inlet in the factory windshield cowl. The foam block was painted black on the visible side (visible through the windshield), so it looks like a foam air filter. That block of foam cut the noise a noticeable amount.

Next, I added a couple smaller foam blocks (each 5 x 5 x 5") that were squeezed into the area between the scoop and the underneath hood framework - near the center and close to the hood latch, to dampen resonant noise. That helped too. The hood now sounds like a normal hood when shut. I plan to add a full-size under-hood pad in the near future, to complete the hood sound abatement portion.

On the "to-do" list is a muffler. Right now, the truck is running straight piped. I'm looking for a muffler that produces a mild throaty rumble without any droning. Since I'll be driving this truck more as a fun daily driver, I want the exhaust note to be a little more civilized.

Beyond that, I'll be installing a rubber bed mat, to help with the echo chamber. It already has a fiberglass bed cover, but not much else in the way of sound deadening...

Let me know if you have any other ideas...