I seem to be going a different direction than most of the sound clips on the other thread - if the truck was as quiet as an idling Prius I would be fine with it.

I have the EFI manifolds, Walker 45166, planning a 2.5" in/out cat,
and probably 2.5" tailpipe to the rear - stock engine and carb so ultra-high performance is not needed but I'd like to get what I can out of the old girl. Any recommendations for a QUIET muffler that won't choke the life out of the engine?

 

I like when people think outside of the "normal" box!

 

Sounds like time to call your local muffler shop(s) and ask them.

 

HoustonDave,

Many years ago, I was mentored by an older gentleman who loved Muscle Cars and was well respected for his knowledge. I remember talking with him about mufflers and he gave me an example. He pointed out that a "quiet" muffler on something like a Pinto was small inside since that worked well for the application because not much flow was required due to the small displacement of the engine.

He then pointed out to me that a large Dodge sedan with 440 engine and single exhaust was quiet, but its muffler was large inside, again due to the flow requirements.

He asked which I thought would work better if the mufflers were swapped?

 

Neither

The small muffler on the 440 is going to be very restrictive.

The large muffler on the Pinto is going to be inordinately expensive and not cost effective.

 

Sounds like the consensus is more or less to a larger but not overly large muffler? I am thinking the tailpipe all the way to the rear should keep it somewhat quieter, but increasing the diameter from stock to 2.5" should drop the backpressure significantly.

 

The exhaust shop can make you a 2.5" tail pipe real easy. Plus, they should direct you to the RV section of mufflers. They are pretty big, but they flow good and are quiet.
"Backpressure" is a 60s & 70s term that is not accurate. The correct velocity for your application is the goal. If you want backpressure, just run a 1 inch pipe.

 

Flyer, if you're still here, explain this one. For a little while I owned a '73 Highway Twin Coach city bus, with a Dodge 440 on propane (these eco-friendly buses, when delivered new to the Sacremento area, were big news). The 440 (I think it was in some way an "industrial" version) had a huge single exhaust running into a really huge muffler, followed by another huge tailpipe. It has been 20 years, but if my visual memory serves, the muffler must have been 10-12" in diameter and a good six feet long. Now, the pipe diameters that the usual experts tell us are the maximum for high performance big-blocks aren't as big as these pipes were, on an engine that only needed a lot of low and low/mid-range torque. And the giant muffler was sort of loud, bus-like, where you'd assume that a city would want quiet buses, other things being equal. What's the deal here?

 

nverenuff - that's OK, I did most of my learning in the '60s and '70s. I think we're actually on the same page, though - I had already planned 2.5" all the way back for
efficiency, just don't need to sound like a "gee, looky me!!" 16 year old with a super-noisy exhaust.

 

I'm with you on the quiet muffler. I have a Harley with stock mufflers and I like them that way. On your question, I can't direct you to a particular make/model, but my thoughts are a muffler that was made for something bigger so it's longer but maybe still 2.5" or bigger in/out.

You may keep an eye out on your local craigslist. I see performance cat back and other mufflers in good shape fairly regular all the time here. Even if it's bigger in (like a modern V8 truck would be) you can always get adapters to go to/from that size cheap at Advance Auto/Autozone/etc.

I also have a brand "C" truck with a 5.7 that has a Y-pipe to 3" cat back to a 3" in/dual 2.5" out that's the stock setup (I just replaced the muffler as the old one was rusted out) You could probably get something like that and even use the stock dual out on yours or any truck as long as the muffler was placed correctly. Just a thought.

Look up these Walker p/n's: 22719 (muffler), 45307 & 45308 (tailpipes)

 

Noted, will do - thanks!

 

I sure do not know Smitty. But when dealing with government entities anything is possible. Maybe they wanted things to be common with existing vehicles to make servicing easier. I dunno. But too big is better than too small.

 

I can hardly believe that the city would have specified muffler and tailpipe dims.

 

Any more suggestions on that super stealth muffler?

 

If you want good flow but a fairly quiet set up just run a Hooker Aero-chamber muffler with a long glass pack between it and the cat. Then you have straight through mufflers for good flow and still be pretty quiet.