The cat will change sound emitted from tail pipe, just what the difference would be I have no clue.

Cats, and carbs unless installed with air pump and all other various emissions devices won't play well together. Running too rich or lean will kill a cat and I suspect make it run real hot. So if your 1969 car is not equipped with all the emission gizmos connected by a rat's nest of vacuum hose I would pass on the add-a-cat idea.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Nope, my 72 definitely did not come with any of that emissions stuff, and that sounds like wise advice.

I'm going to be tweaking and tuning this thing for the next few years, going through various stages of upgrades of air flow and compression, possibly to EFI and turbo at some point down the road. I know for fact I will be dumping fuel out the tail pipes at least at some point during the tuning process. It may work when the car is running perfect AFR and such, but then again shooting fireballs out the back would be fun, too.

I suppose if the dang thing is clean and running right, it should not be dumping too much smelly crud out the tail pipes anyway. Thank you for confirming my theory.

I'll do more research on the shapes and sizes of possible resonating chamber options and maybe just pick one option and try it, and if that does not work as I want, I can always change it later... at least exhaust work isn't the most expensive thing in the world... relative to just about everything else.

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1972 Plymouth Duster:
- 225ci
- Offy 4-Barrel Intake
- Weber 38/38 DGES
- Clifford headers
- Split 2.25" dual exhaust
- Pertronix digital ignition conversion
- Black-out custom digital gauges
- Front disc brake conversion
- Viper Blue

Wonder how loud this slant would be?
Plodge 1/2 Plymouth 1/2 Dodge by Mike Welch, on Flickr

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51 Plymouth Cambridge with / 6