Mufflers VS Catalytic converters

[Nima]

Hi:
This might be an stupid question but I have to ask. I know catalytic converter are generally more restrictive than mufflers and they can cost some HP and maybe torque, besides I think they are more expensive than mufflers. My truck, being a 1967 and carburated, has this old car smell. I can't get rid of it doesn't matter how much time I have spent on tuning. I wanted to ask if catalytic converter can filter some of that smell?!! If they do, how about replacing my mufflers, which are basic jegs turbo mufflers, with pair of high flow converters? My truck power train is just a basic 350 and 3 speed tranny.
I have a small two car garage and by the time I start the truck and pull it out to let it warm up, I hear the wife that the whole garage smells, and some times it leaks to the house since it is an attached garage.

[jdalexa84]

Catalytic converters are designed to burn the unburnt fuel in the exhaust gasses. Putting them on could help with your problem. I would keep the mufflers because they serve a different purpose.

[Nima]

Please correct me if I am wrong, the mufflers are there to muffle the sound and create some level of back pressure. I would guess the converters will do these jobs as well, to some degree.

[jdalexa84]

To some degree yes but have you ever heard a newer car that has lost the muffler? They are extremely loud. And they have both

[special-K]

Do you back it into the garage? Pulling nose first should help, if you aren't already. Starting any vehicle in the garage is going to fill it with exhaust. I guess your garage floor is pretty level. How about making little ramps to pull the front wheels onto. You could roll it out of the garage, then start. I get fumes if a vehicle (old or new) runs in the driveway with the exhaust aligned with the mudroom door. I just roll forward first.

[Steeveedee]

Use an exhaust fan with a timer. If you put on cats, you will not experience all that much restriction or back pressure. Check and see how many GM vehicles came from the factory with dual converters. It was common on '70s Ford products, but back in the day, the only GM vehicle I saw with dual converters was the top of the line 455 Firebird Trans Am.

[96blazr]

Originally Posted by Nima

Hi:
This might be an stupid question but I have to ask. I know catalytic converter are generally more restrictive than mufflers and they can cost some HP and maybe torque, besides I think they are more expensive than mufflers. My truck, being a 1967 and carburated, has this old car smell.

Seriously!!?? WTF kinda question is this?? It's a1967, THEY DIDN'T HAVE CATS, NEVER HAD CATS, NEVER USED CATS!! Why would you even think about putting Cats on any vehicle from 1967? Just run your Mufflers, whichever you choose, and be done with it.

[leddzepp]

If you read the entire post, he is asking if it will help reduce the exhaust smell.

[Bigdav160]

Catalytic converters don't do anything until they are heated up. I don't think they are going to help the OP's problem.

[El Dorado Jim]

I really don't know why you would want to waste the money on cats, I am glad I only own '75 and older vehicles here in Ca, so I don't have to run cats or even smog my vehicles

[Highlander72]

I hear ya. The exhaust smell didn't bother me when I was a kid, but today's gas is a lot different.
Cats do need to get hot to be effective, I'd run just one up near the engine because of that, then split into duals if you want, or just run a big single.

['68 Newtricks]

I like Special-K's idea of running the truck onto a couple small ramps. Open the garage door, put in neutral, roll out and start. Best way to do it.

If you run cats, they need to be as close to the cylinder heads as possible. Running two small ones at the collector will work best for cutting down on morning smells. The larger cats will take longer to heat up and thus longer to be effective. Neither small or big cats will help contain the smell in the garage, just not enough time for them to heat up.

Do the ramp thing or exhaust fan on a timer. I think you'll be happier with the outcome than changing your exhaust.

[special-K]

Originally Posted by 96blazr

Seriously!!?? WTF kinda question is this?? It's a1967, THEY DIDN'T HAVE CATS, NEVER HAD CATS, NEVER USED CATS!! Why would you even think about putting Cats on any vehicle from 1967? Just run your Mufflers, whichever you choose, and be done with it.

Originally Posted by El Dorado Jim

I really don't know why you would want to waste the money on cats, I am glad I only own '75 and older vehicles here in Ca, so I don't have to run cats or even smog my vehicles

If people voluntarily kept their vehicles properly tuned there would be no need for mandatory emissions testing. I don't like the testing any more than anyone else. In fact, I have never owned a vehicle required to go through that, either older or diesel. But...on the '90 Blazer I bought new for my wife, I wanted dual exhaust for the 350. It's what I have always done. My exhaust guy wouldn't do it because the state dept of environment had come down on the state dept of trans for not enforcing the laws. The law reads the exhaust must run same size same design same exit point as factory for that particular engine in that vehicle. They were fining and taking the (emissions) license from violators. I finally found a shop not concerned and had my true dual exhaust using 2 Flowmaster mufflers and 2 Thrush full flow converters run. With the better flowing less restrictive exhaust the Blazer made more power using less throttle while emitting less harmful gases than factory. I reduced the emissions output while breaking the emissions laws.
This got me to thinking why not on an old truck? I came up hating converters, but if they don't hurt performance with the result being cleaner air than what's the harm? This was 25 years ago and I was looking ahead at what they might do about older vehicles emissions in the future. Having my exhaust guy turn down my dual exhaust job sent my mind reeling and that's where it ended up. If keeping these trucks registered required installing catalytic converters I would be willing. If someone wants to do this on their own I say more power to them.

[67ChevyRedneck]

I did a little reading on this myself not too long ago (I have a 65 Mustang with the same problem, car runs great, is tuned right, but backing out of the garage in the morning is a little stinky), and the general "consensus" seemed to be that carbureted engines, even properly tuned, just release too much unburnt fuel and would likely burn up a cat. I don't know how true that is or how long it would take, maybe it does, but would take a few years?

The best option would be adding a fuel injection kit and cat to your motor, but last I checked, most kits are still around 2K... for that price it would be LS time.

[Nima]

Well, thanks for all the posts. I guess making a small ramp would be the fastest and cheapest option while I decide on more permanent solution.
I was also thinking about a fuel injection (TBI, TPI or LS conversion) but the cost of entry is still too high for me.
Thanks again

[MARKDTN]

You can almost change to fuel injection for what Cats cost. My '83 K20 has dual exhaust with hi-flow cats and no mufflers. I had an '89 IROC with dual cats (California emissions) and ran it for a while with no muffler. Both sound weird. You really need a resonator at least with a Cat. But I agree with above. NO WAY would I voluntarily add Cats to a vehicle that did not require it.

Cost of small-block fuel injection is dropping. I went to the AACA swap meet in Nashville over the weekend. I always carry a TPI to sell, or at least draw people to my table. I was asking $250. There were people reporting buying complete TPI units for $125-150. So cost of entry for TPI is not that high really. Lets say a $150 intake (not from me), $200 rebuilt Bosch injectors, $25 ECM, $100 PROM, $75-100 fuel pump, and a $250 harness. $20 oxygen sensor. Optional $75 VSS, but I would run it. Some fittings and gaskets and air cleaner. You could take some $$ off if you used a 3.1 Corsica or Caviler harness and adapted it (or found a Camaro cheap enough). You might find a tank that had an internal pump or you might use external. You can do the swap in a weekend. I love the way a TPI runs. I have 2 of them running. The visual appeal is awesome. If I was doing a big build I would do LS, but if you have a good running long block small block, TPI is great.

[Eddie H.]

Catalytic converters need to warm up for a few minutes before they start working, and even then, they require a very precise fuel/air mixture in order to reduce emissions efficiently.

[ironroad9c1]

Yea a cat on a carbed engine would fail pretty quickly due to the amount of unburned fuel in the exhaust.

[Grumpy old man]

The whole emissions/inspection saga is political BS when you consider many states don't even bother . And when you consider all the other countries (China) that are still belching poisonous contaminants into the atmosphere so we can buy a reproduction mirror for $19.95 are we really kidding anyone ? Look at Flint with leaded water ...There are a lot of people down stream that no one is even talking about yet ...

[davepl]

Originally Posted by 96blazr

Seriously!!?? WTF kinda question is this?? It's a1967, THEY DIDN'T HAVE CATS, NEVER HAD CATS, NEVER USED CATS!! Why would you even think about putting Cats on any vehicle from 1967? Just run your Mufflers, whichever you choose, and be done with it.

I'll answer that, because I contemplated it.

They never had stereo radios either, but people add those.

Old cars smell. They just do. My clothes smell like gas, my hair smells like gas, and my truck doesn't run rich. It's simply because they're inefficient and a lot of unburned fuel comes out at idle.

I don't care about the emissions on a "pleasure" vehicle like this, it's not about that. Just the smell.

You may not care. But some wives and girlfriends do.

My concern was that they're -so- much worse than modern engines (primarily the combustion chamber and cam) that there would be too much extra fuel to burn. My '75 Monte Carlo had cats and a carb, so they did build them that way. And it wasn't a computer-controlled Q-jet either, just your basic 2bbl.

[Grumpy old man]

http://www.autonews.com/article/2008...ways-to-comply

[special-K]

Originally Posted by Grumpy old man

The whole emissions/inspection saga is political BS when you consider many states don't even bother . And when you consider all the other countries (China) that are still belching poisonous contaminants into the atmosphere so we can buy a reproduction mirror for $19.95 are we really kidding anyone ? Look at Flint with leaded water ...There are a lot of people down stream that no one is even talking about yet ...

Yeah, I always look to those who are doing a worse job for an example of how to improve myself

[BigRed76]

Fuel injection with no cats will do you better than carbureted with cats.

[MARKDTN]

Originally Posted by BigRed76

Fuel injection with no cats will do you better than carbureted with cats.

I agree!

And to those who said that you can't do carbed with cats-I think you need to look at all American cars from 1975 into the mid to late 80s. The first successful domestic electronic fuel injection was the 1982 Corvette, but many cars didn't get it until much later in the '80s.

[70cst]

The smell is part of living with old school rides ...

I luv it