Removed Emissions - Exhaust Smells to High Heaven...

[PWagon]

I have a 86 K5 Blazer with a 305, and the exhaust (tail pipe) has always stunk. I suspected I had a cracked head, so I pulled the engine (with 180,000 miles) for an overhaul two months ago. I removed the stock intake manifold and carb and replaced them with an Edelbrock intake and 600 CFM carb. The carb is calibrated for economy (my thinking was less fuel will equal less smell at the tail pipe). I also installed a brand new MSD Streetfire distributor, plugs, wires, and new catalytic converter. Everything fuel related is brand new or rebuilt, and my exhaust still stinks (like burned fuel - not rotten eggs). My question is this. Does the factory emission systems really remove the stink from burned fuel? All my life I have hated all those emission hoses, "coffee can" looking containers, EGR valves, and all that other emission junk. Do I really need to hook that crap back up to remove the stink, or am I missing something here? I would really appreciate your input on this.

 

[Jessie James]

I had a similar issue with my 90 TBI Blazer. PO had removed the catalytic converter and I couldn't drive it without smelling like I bathed in gasoline cologne. My wife refused to go in the truck. I put a new cat in and it's completely gone.

So in my experience ... yes, the emissions stuff does make a big difference. YMMV though.

 

[NorCal_Chris]

I have a 86 K5 Blazer with a 305, and the exhaust (tail pipe) has always stunk. I suspected I had a cracked head, so I pulled the engine (with 180,000 miles) for an overhaul two months ago. I removed the stock intake manifold and carb and replaced them with an Edelbrock intake and 600 CFM carb. The carb is calibrated for economy (my thinking was less fuel will equal less smell at the tail pipe). I also installed a brand new MSD Streetfire distributor, plugs, wires, and new catalytic converter. Everything fuel related is brand new or rebuilt, and my exhaust still stinks (like burned fuel - not rotten eggs). My question is this. Does the factory emission systems really remove the stink from burned fuel? All my life I have hated all those emission hoses, "coffee can" looking containers, EGR valves, and all that other emission junk. Do I really need to hook that crap back up to remove the stink, or am I missing something here? I would really appreciate your input on this.

Its strange that the new Cat didnt tone it down.

The charcoal canister is to keep gas fumes down, not neccisarily anything you would smell... Old gas tanks vented into the atmosphere, but now with sealed tanks and evap systems that has changed. Charcoal canister holds the gas fumes untill the engine is started, then the purge valve lets those fumes into the engine via vaccumn to burn the fumes.

The purpose of the (EGR) valve is to meter a small amount of exhaust gas into the intake system, this dilutes the air/fuel mixture so as to lower the combustion chamber temperature. Excessive combustion chamber temperature creates oxides of nitrogen, which is a major pollutant.

There will always be some unburned fuel in the exhaust. This increases hydrocarbon emissions. Thats why there are the air pumps . Inside the exhaust manifold there is sufficient heat to support combustion, if we introduce some oxygen than any unburned fuel will ignite. This combustion will not produce any power, but it will reduce excessive hydrocarbon emissions, That is the Air pumps purpose.

So i think having the EGR and air pump would be your best bet for lowering the smell

 

[rufusbooth]

The Cat should have taken care of most of your smells.

One thing to clarify is if the smell is 100% raw fuel from the tank vapors or if it is unburned fuel coming from the exhaust.

If it is raw fuel smell from the tank you will need to get the EVAP system hooked up. It has 0 impact on HP and will remove any vapors escaping from your tank.

If it is unburned fuel in the exhaust then there are a couple of suspects.

1. The carb is not tuned properly. It may be too rich. You mentioned that you had an "economy" tune on it but how was that accomplished? Was a wide band O2 sensor used on your engine or was it a generic tune from a carb tuner done off the truck? If the truck is REALLY rich the cat could have been destroyed rendering it useless and doing nothing to reduce the smells from the truck. To truly tune the carb you need to jet it on a dyno with a wide band sensor before the cat. You would be amazed how much better a well tuned carb will run when tuned properly and not on a guess.


2. The cat is too large or too far away from the motor. Either condition will cause the cat to run too cool. If the cat can not reach operating temp (about 750 degrees) it will never be able to "fire off". What size cat do you have and where do you have it mounted (how far away from the motor)?

Also, I am assuming that the smell never goes away? Remember that in order to operate properly that cat needs to be hot. On a cold start it will not be working and you will smell fumes. Once the cat is up to temp the smell should go away. By removing the air injection system this process will take longer than normal. Adding the additional air into the exhaust forces the cat to fire much earlier than without.


Hope that helps,

Cheers,


Rufus

 

[Sqeejo]

The Cat should have taken care of most of your smells.

One thing to clarify is if the smell is 100% raw fuel from the tank vapors or if it is unburned fuel coming from the exhaust.

If it is raw fuel smell from the tank you will need to get the EVAP system hooked up. It has 0 impact on HP and will remove any vapors escaping from your tank.

If it is unburned fuel in the exhaust then there are a couple of suspects.

1. The carb is not tuned properly. It may be too rich. You mentioned that you had an "economy" tune on it but how was that accomplished? Was a wide band O2 sensor used on your engine or was it a generic tune from a carb tuner done off the truck? If the truck is REALLY rich the cat could have been destroyed rendering it useless and doing nothing to reduce the smells from the truck. To truly tune the carb you need to jet it on a dyno with a wide band sensor before the cat. You would be amazed how much better a well tuned carb will run when tuned properly and not on a guess.


2. The cat is too large or too far away from the motor. Either condition will cause the cat to run too cool. If the cat can not reach operating temp (about 750 degrees) it will never be able to "fire off". What size cat do you have and where do you have it mounted (how far away from the motor)?

Also, I am assuming that the smell never goes away? Remember that in order to operate properly that cat needs to be hot. On a cold start it will not be working and you will smell fumes. Once the cat is up to temp the smell should go away. By removing the air injection system this process will take longer than normal. Adding the additional air into the exhaust forces the cat to fire much earlier than without.


Hope that helps,

Cheers,


Rufus

Not to hijack but this is happening to me as well. My cat is the stock cat and ehaust system minus the AIR system. Would carb tuning be the culprit or a bad cat? I was going to go aftermarket on exhaust system during the engine build but def want to quit smelling like I bathe in gas

 

[Blue85]

The cat is the biggest thing in getting rid of the smell. The AIR pump helps the Cat burn correctly - so there's no point in having the AIR pump if you don't have the cat. Adding/removing the cat makes a night and day difference in the smell.

 

[Cornfield creations]

I got my quadrajet tuned pretty good and I still have my cat on there and it smells like a hot runnin race-car. Course if you got your cat from a discount parts store the effect it has is intended for will be minimalized. Their cats are cheap because the necessary metals ( irodium, platinum) are barely there. Therefore they are known to kick check engine lights on ob2 systems, but still has the same effect on none computerized vehicles where it doesn't convert the gases or burn fuel efficiently enough.

 

[rocknerd]

bought my 88 (71 350 motor converted to tbi) without a cat and the smell was unbearable. Installed the stock cat that was given to me with the truck and it made a very small difference. Truck runs rich so looking into timing and injectors, but a cat isn't necessarily the magic answer. it may work, and it will probably help, but in some cases it may not.

 

[Cuztom Racing]

Good topic! Sounds like you have a carb issue.. Im also wanting to remove all that crap on mine, the charcole canister and what is the ball looking thing with one single hose coming from it??

 

[xCaliK5x]

Mine is left 100% stock on emissions. It runs great with it there, I won't mess with it.

 

[Jessie James]

what is the ball looking thing with one single hose coming from it??

I think that is the vacuum reserve so your power brakes work when under power or when vacuum is not present ... correct? Anyway, removing that might not be the best idea if you like your brakes to work.

Someone will surely correct me if I am wrong!

 

[tRustyK5]

It's for cruise and AC/vent control. Under heavy throttle you get near to no vacuum, without that vac resevoir you'll lose your vent position as they're vac controlled.

Brake booster vacuum is the big ugly thing the MC is bolted to.

Rene

 

[Duntz00]

You need to have the carb tuned right, I took all the emissions junk off mine and running headers with no bad smell.

 

[djtejas]

Canister/Gas Smell

On my 83 Blazer, the canister on the passenger side is for the AC/Vent/Heat controls. The canister on the driver's side is for the cruise control.

I have no emissions on my Blazer...no charcoal canister, egr, or cats. I have no gas smell inside the engine compartment or at the exhaust. I did spend a day tuning and calibrating my carb to make it run as best I could.

I have an Edelbrock 1405, Edelbrock Air-Gap intake, Edelbrock Performer Plus cam, and headers...I get 16 mpg...it didn't get that when it was new with the smogged 305.

 

[mnstrburbon]

Sounds like the smell is a timing issue double check the timing and make sure you have the vacuum advance hooked up to the proper port on the new carb.