What type of exhaust does your 273 have??? show some photos!!!
so…. At the end, stock header, 2.5 H pipe, 2 super turbo dynomax 17733, 2.5 end pipe.
This would give me great growl and a vintage muscle car feeling??
Headers can produce a unique sound at both ends; yes. and the more "performance-built" the engine is, the more it sounds like a muscle car.
But a stock-cammed 273/318, thru log-manifolds, and especially a lo-compression one, I'm gonna say, um, no, you wouldn't get a "vintage muscle-car feeling" ; at least not at low rpms.
Here is my experience with the above scenario, albeit with a 318
The cam in your engine has the same/similar specs as has the 318, namely, it is a "short-Period" cam, with a loooog period power stroke, about 118 degrees. compared to a race cam of less than 100, and a typical street cam around 106/108.
If you want a growl in such an engine, with a long powerstroke cam, like as is the 273cam, put small pipes on it to keep the energy up, so the still hot, supposed to be still expanding exhaust gasses, can "pop" when they hit atmosphere. Otherwise it's gonna sound, IMO, I wanna say, like crap.
Most of the sound that the hi compression 340s made, came from the high-energy exhaust, chugging down the 2.25 pipes and popping modestly, at the outlet; which pop, was shaped by the rectangular tips. Take any one element away, and IMO, the sound went away.
IMO, yur never gonna get that "feeling" that you are looking for, with a lo-compression, stock-cammed, 273/318, thru dual exhaust; as there is just not enough energy left by the time it gets to the rear bumper ... unless maybe you wrapped the pipes, lol. The energy has to stay in the gasses. If they give up their heat to the cylinder-walls thru a long power stroke, and to individual header-pipes, and to large-diameter exhaust pipes, and to 3-pass mufflers, then by the time they get to the end of a 2.5" tail-pipe, you practically gotta suck them them outta there, especially at idle.
Every chamberfull of burnt gasses starts out, occupying a volume of 1/8 of the engine's displacement, plus the chamber, which for a 273 is about 642cc at 8/1 Scr. At idle, by the time that slug gets some 12ft to the bumper, it has given most of it's heat away on the trip, so it staggers out the end and falls to the ground, which in a dual exhaust system, is followed by three others, staggering into the world.
The point is that no matter how you tune the 273 dual exhaust, it will never sound like a performance engine, until you build it into a performance engine. and even then, you gotta deal with the tiny amount of exhaust trickling out the ends.
But you know, some guys say that the original hi-po 273 2-into-1 had a distinctive sound. IDK; I never heard one; in 66 I was only 13. I never even saw an early Barracuda until some 10 years later.
Here's what I know, if you try to jam your 273 exhaust down a small enough pipe to make it sound like a performance engine, then it's gonna lose power as it revs up, compared to a free-flowing exhaust. Bad sacrifice in my opinion.
So what do you do?
IDK, but
I can tell you what I would do if I had a lo-compression 273; If I was looking for sound; notta chance would I back that thing out my garage at 8/1 Scr and expect it to sound like a vintage muscle car. What I'd probably do is keep the original single exhaust and put a glasspack on it.
But you know, before that, I would try it with a length of straight pipe taking the place of the muffler, cuz I know you want to too, lol. and, I would try a rectangular, no baloney-slash, exhaust tip. Badaboom!
Now, if you put a hot cam in there with a hot compression ratio, that would be a whole 'nuther conversation.
But I gotta tell ya, notta chance would my 273 stay at 8/1, unless it gets supercharged.