I cut my muffler off to install a magnaflow and was shocked how quiet it is with no muffler at all…

When flooring it, the air intake is louder then the exhaust in the drivers seat.

This is a stock 305tbi. Is that 35 year old stock cat absorbing all the sound? If so, any suggestions for a modern cat? Not sure I’m willing to go cat less yet.

 

I remember being perplexed as to why my stock H.O. exhaust is so loud (not too loud). I later discovered a previous owner gutted the CAT...

 

Low power + exhaust manifolds + tiny exhaust piping + cat = quiet

 

cats are great mufflers

 

Who runs cats anymore.

 

Hold up, guys.


This^ is totally true. The cat does act like a muffler, to an extent.....BUT, hold up a second.
^That statement^ instantly throws a red flag. The intake should definitely should not be louder than an open cat exhaust. UNLESS......unless what? Unless the cat is clogged. That will make the exhaust quieter....and make the intake a whole lot louder! I would rig a pressure gauge to the o2 bung and go drive it WOT, see how much exhaust pressure it's building.

 

Cats are good for blue hair people w/ nose rings, shower hooks in forehead.

 

Any decent high end, high dollar build has cats on them.
No one wants to smell like exhaust.

 

Agreed. Comments like those above show ignorance. Correlating people's appearance to catalytic converters is just stupid.

 

If the car is whisper quiet from the exhaust, the cat is probably clogging up. Especially if the muffler has been removed.

I remember when the cat on my GTA clogged. And it wouldn't rev over about 3-4k in neutral.

 

I Never ran cats on these cars or anything else i could remove those parasites from. Never smelled like gas either. If your car smells like gas after removing the cat then you have an exhaust leak

 

Hydrocabons smell like gas, because.....they're gas. lol. I have no cats on the Kart...it reeks at a stop light. I'll be putting cats on it. Painting the technology as "evil"/dumb/parasites/...whatever, is a pretty untenable position to take. Using or not using one is a personal decision and has nothing to do with hair color.

And....psssst! There are good cats out now days (and for the past 20 years or so) that consume approximately zero power...while reducing emissions by >90%.

 

My brother's 305tbi Camaro was pretty damn quiet with a Magnaflow muffler and stock cat in place back in the day, I remember seeing the disappointment on his face when he first started it up after putting the muffler on lol.

As far as smelling like gas due to not running cats, I've never noticed it on myself or anyone else and no one has ever pointed it out to me.

 

Well, the old cats (stock thirdgen) are parasitic compared to modern cats. Cats are good to have, until they clog up or stop working...

 

Agree with that, for sure.

 

Wow, that some sh*t my grand father would say!

Actually he wouldn't cause he's been dead for 25 yrs and he died an old man. But you get the point!

 

Well even though it's not true, I thought it was funny as hell. LOL!!!...

 

I purchased a pair of Magnaflow 99206HM replacement converters for my 5.3 build. I can't comment on sound, as I don't have the new engine in the car yet. I'd think a single would be plenty for the 305.
https://www.summitracing.com/parts/mpe-99206hm

 

Okay, this makes sense. I figure I'll try to disconnect the cat and drive it around for a bit to see if that was the case. If so, I'll just order a universal one and put it in place.

 

It is a TBI car. Like a LG4 car the whole exhaust system chokes the engine from the cylinder head ports out. You could run that car with an open T-pipe after cutting off the cat and it would still be quiet because the stock exhaust manifolds and T-pipe might as well be a cork. The whole system is restrictive trash, the manifolds, T-pipe, catalytic converter, catback, or as I have said many times before the whole exhaust from the cylinder head flange to the tailpipe. The later model speed density TPI 305s were the same exact long block. The difference between the 205 hp and the 230 hp version was entirely the L98s larger manifolds and dual catalyst Y-pipe. The 205 hp version had the LG4/L03 exhaust and the 230 hp version had the L98 350 exhaust. The 205 hp version sounds like an old Hoover vacuum cleaner with a full bag. The 230 hp version actually had a decent and somewhat aggressive exhaust tone.

I also agree with keeping a catalytic converter because I hate the smell of unburned hydrocarbons and having the interior of a vehicle reeking of fumes idling around town and in traffic when the HVAC is operating.