Stock 305, thoughts on 3” tubing?

[JRLeadfoot]

Of all the exhausts I’ve had on various vehicles the best sounding one ever was my 96 Chevy truck. I had 3” tubing with 4” (maybe 5” can’t remember) tips. I had them weld in a y pipe instead of the muffler and even though it was a 4.3 Vortec V6 it sounded like a monster. Even with a muffler it was deep.

I have a feeling that the deep rumble it had was mostly due to the large piping (acoustic science says that the longer the wave the deeper the sound, the shorter the higher. A bigger pipe should equal a longer wavelength right?

But, those huge pipes on my truck absolutely killed my torque and hp it seems. I don’t want to reduce an already anemic hp number.

Every system I see seems to use 2.5” tubing with various types of turbo mufflers etc. Can someone recommend the best bolt on kit that will give me a super loud, deep rumble?

 

[pagrunt]

It'll be a combination of pipe size, bends, exhaust design & mufflers. 3" on a 305 is over kill & make it perform worse due to the lack of back pressure. Shop the mufflers & go from there.

 

[JerRol79ElCam]

The exhaust needs to equal the engine for torque and horsepower efficiency. A stock 305 needs no more than 2 inch pipe. if you have mild modifications you could go to 2 1/4. If you go to 300-400 horsepower take it to 2 1/2. I see/hear so many cars and trucks that make a lot of noise with big pipes and can't move out of the way of a moped. It's a waste if you don't know how to tune it properly.

 

[78chevolds]

IMHO, 3" is overkill. I have 2.5 with no cat on my 78 Camaro with a 2BBL 305. Majority of the Camaro's of the members I know typically run 2.5" on the 350's and 305's.

 

[motorheadmike]

I dunno what I am doing... and I cannot stop!

1992 Camaro "The Lady Mullet" Z28

Since it looks like you were having barrels of fun I would assume you missed the auction, so I got you these

gbodyforum.com

That is dual 2", into dual 2.25", into a single 3", into a 4" muffler. LOL.

 

[ck1984]

Of all the exhausts I’ve had on various vehicles the best sounding one ever was my 96 Chevy truck. I had 3” tubing with 4” (maybe 5” can’t remember) tips. I had them weld in a y pipe instead of the muffler and even though it was a 4.3 Vortec V6 it sounded like a monster. Even with a muffler it was deep.

I have a feeling that the deep rumble it had was mostly due to the large piping (acoustic science says that the longer the wave the deeper the sound, the shorter the higher. A bigger pipe should equal a longer wavelength right?

But, those huge pipes on my truck absolutely killed my torque and hp it seems. I don’t want to reduce an already anemic hp number.

Every system I see seems to use 2.5” tubing with various types of turbo mufflers etc. Can someone recommend the best bolt on kit that will give me a super loud, deep rumble?

yeah 3 " for 150 hp 305 is way overkill. I did a side exit 3 inch exhaust on my 300 hp LS and i think i sacrificed TQ but i do have that Big Block burble sound.
my home fabbed y-pipe with no cats feeds directly into a 3" Insynerator Race Series - One Chamber Muffler and i only have 3 ft of 3" pipe so im not sure if i could get much scavenging effect even if i went down to say 2.75 inches with only 3 ft tailpipe?
anyone have that CFm chart for hp and proper sized single exhaust?

 

[Michael Watts]

With a 305 I would run a 2 1/4 true dual exhaust with dual mufflers .And dual High Flow catalytic depending on the state emissions law.

 

[64nailhead]

With no sarcasm intended, a stock 305 with dual exhaust is not going to limited by 1.75" pipes. And perhaps 1.5". Consider a 4 banger making 80 hp can live happily with 1.5", so half of a 305 that 75hp is not going to hampered by 1.75". 3" is just way overkill.

I ran a single 3" on a 327 with a turbo making 15-16psi that ran just fine. The 3" single didn't hamper a thing at darn near 500whp.

 

[oldmansmonte]

My opinion, 305 is not a performer, so do it! Doesn't make much power, can't sacrifice much power. You'll certainly have the thunder with 3"! If that's what you're after.

 

[ck1984]

With a 305 I would run a 2 1/4 true dual exhaust with dual mufflers .And dual High Flow catalytic depending on the state emissions law.

every application will be slightly different but on average , more is not better for low end Tq. maybe loudness but not TQ. if u r going more than 10% over manufacturer size on a stock engine u r making things worse, especially w/o a tune

Area of a circle is Pie x R squared
so a 3 inch single system is 3.14 x [1.5x1.5]=7.065[overkill on stock 80s 305]
a dual 2.25 system equals 3.14 x [1.125x1.125]x2pipes=7.94[way overkill]
Unless you put a blower on that dusty old 150 hp 305 i think, no i know, dual 2.25s is overkill, dual 1.75 would be sufficient and not lose any scavenging effect and low end tq.
this is exactly what my cutlass 305 had on it, no cats, just dual 1.75 flowing thru glasspaks

one shitty thing about stock old 305s i noticed in my teardown was that warmup valve in passenger manifold, that even when open had to be blocking a very signifcant amt of exhaust flow, should be removed if you value power over faster warmup.


2 smaller duals will always give you a higher pitch, more poppy raspy sound.
I put my 300 hp LS on a single 3 inch just for the burbly , low pitch Big Block sound, and it does sound like a BBc and im not sure i wouldve saved any lowend tq going with single 2.75 inch since my exhaust tube is so short, only 3 feet.
if you have a stock 305 and want bassy burbly Big block sound , go with a single 2.5 inch system and maybe a much larger tip, like 3-4 inches.

ive done this exact trick on my civic, i cut the muffler off entirely and just welded on a 14" long 4 inch tip and it made the 1.8L 4 cylinder sound like a 3 L v6
im sure all my neighbors hated it when i got up at 630 am to goto work , cuz for that first ten sec at startup it was extra loud.
not as loud as my LS with single chamber muffler and 3 inch system but now i live more rural so less neighbors

removing cats and resonators also makes a big difference on sound
some of the best sounding cars have longtube headers, no cats, no resonators and straight thru mufflers.