47-59 cat converters

[nvrdone]

anyone added Catalytic Converters to a dual exhaust system? my wife complains about exhaust smell from my 327 and a friend recomended adding cats to clean up the smell. any thoughts or ideas would be appreciated. Thanks

[MiraclePieCo]

Cats to clean up the smell? Sorry, but they do just the opposite. When I drive over my local mountain passes the rotten egg stink from all the hot catalytic converters is nauseating.

Maybe your truck is running too rich?

[mr48chev]

If there is a smell it isn't because of a missing cat. It is because the fuel system isn't adjusted correctly or your exhaust exits out from under the truck in the wrong place. It does exit from out under the truck and not under the truck?

[nvrdone]

ok, you got me. the exhaust does dump straight out in front of the axle. and maybe the carb is running rich. maybe i should leave it that way & my wife will want to stay home. JUST JOKING !!!!

[MiraclePieCo]

Haha, try some fuel fragrance. My favorite is Groovy Grape:

https://www.powerpluslubricants.com/...ragrances.html

[mr48chev]

When I lived in Texas I had a buddy who had a 60's Mopar with a big block who ran turbos with the exhaust dumping down in front of the rear axle under the car. Serious fumes while cruising around town and a headache making drone going down the road. I rode with him to the drags at Little River once and about hooked a ride back with someone else.

No excuse for a carb that isn't tuned right so it doesn't run rich though.

[nvrdone]

mpc - what kind of a scam is this fuel fragrance ???

[MiraclePieCo]

Originally Posted by nvrdone

mpc - what kind of a scam is this fuel fragrance ???

There are dozens of scents, including one called Reefer Madness that makes your exhaust smell like burning marijuana:

https://www.powerpluslubricants.com/...ragrances.html

[mr48chev]

That is too funny, scented exhaust.

[1project2many]

Originally Posted by nvrdone

mpc - what kind of a scam is this fuel fragrance ???

Not a scam. It works. Covers the smell of illegal... err... "reformulated" race fuel. Also helps make nitro smell better.

anyone added Catalytic Converters to a dual exhaust system?

Cats can clean up excess fuel smell but they also need oxygen to work. If your exhaust is too rich the catalyst will have trouble getting warm enough to make a difference. Part of the reason OE's add air pumps is to help get the cat warm when the engine is cold and running rich. That's also part of the reason OE programming for EFI swings rich / lean / rich.

Some cam designs are more likely to cause rich exhaust at idle. Too much overlap at low engine speed can allow exhaust gas into the intake and can cause partial combustion. It actually acts like EGR by cooling and slowing the reaction. Are you running a stock cam?

No excuse for a carb that isn't tuned right so it doesn't run rich though.

Agreed. Get the carb tuned.

[nvrdone]

ok, no its not a stock cam/ engine etc. its a 327 block, bored 30 over, 4 bolt mains, 194 heads high lift cam & a whole lot of stuff i cant remember. it was originally built for a sprint car & wound up in my truck in 1973. so i will start by tuning the carb & timing & see if that helps.

[dennislbrooks]

Ok, I'll bite. I did run cats on my 67 swb with a crate 350 with an edelbrock 600. They need to be up near the engine to work correctly as they do need to be hot. And yes I think the exhaust smell was better with them. I agree running too rich is a noxious smell. Tune and if that does not do it run an oxygen sensor and gauge and run cats. Run unleaded.

I do not run cats now with a bbc and a qjet but I would not be afraid to run them again if sized correctly.

[mr48chev]

The only viable reason to run cats on a pre 75 rig is that your state requires them because of the year model of the engine you installed. In the "must meet emission requirements for the year model of the engine installed."

It works the other way around too. I know of one guy in this state that stuck a mid 60's 327 in an 81 Camaro during a rebuild (car was bought from the same outfit I bought one from with a bad engine and salvage papers) and flunked the state inspection. The guy pulled the 305 out, stuck a 327 he had in and took it to inspection and the inspector failed it. That from the same inspector who checked my 81 and told me that it had been severely wrecked and repaired once before. My wife got so many tickets in it that she got her license suspended and I sold it.

[layinrocker65]

Adding cats can help with exhaust smell but you should try tuning and moving the exhaust outlet as far back as possible before doing anything else. And have the exhaust point towards the back.

There’s a reason people always complain about the exhaust smell after removing cats from cars(mostly modern cars since the cats are more effective this making a bigger difference).

[Jemezcrusher]

Originally Posted by 1project2many

Not a scam. It works. Covers the smell of illegal... err... "reformulated" race fuel. Also helps make nitro smell better.




Cats can clean up excess fuel smell but they also need oxygen to work. If your exhaust is too rich the catalyst will have trouble getting warm enough to make a difference. Part of the reason OE's add air pumps is to help get the cat warm when the engine is cold and running rich. That's also part of the reason OE programming for EFI swings rich / lean / rich.

Some cam designs are more likely to cause rich exhaust at idle. Too much overlap at low engine speed can allow exhaust gas into the intake and can cause partial combustion. It actually acts like EGR by cooling and slowing the reaction. Are you running a stock cam?


Agreed. Get the carb tuned.

Sorry, cover up the smell of nitro? Blasphemy! When Ron Capps was sponsored by Brut years ago they put that crap in his nitro funny car. Smelled horrible!

[1project2many]

Sorry, cover up the smell of nitro? Blasphemy!

I know. Some of those tech guys have no sense of adventure.

When Ron Capps was sponsored by Brut years ago they put that crap in his nitro funny car. Smelled horrible!

What? Brut? In a Funny Car??? That just ain't right.

[mr48chev]

Originally Posted by layinrocker65

Adding cats can help with exhaust smell but you should try tuning and moving the exhaust outlet as far back as possible before doing anything else. And have the exhaust point towards the back.

There’s a reason people always complain about the exhaust smell after removing cats from cars(mostly modern cars since the cats are more effective this making a bigger difference).

You must live in a far different world than I do as I have never once since 1975 when cats became required on US cars heard or read that removing them may cause noticeable smells until I read your post. Where do you get this information?

Bad cats that need to be replace stink. The exhaust on my 2K Cad DTS that I don't have anymore stunk with some brands of gas but the cats were in place and functioning and the car was tuned.