V8 Jeep - Carburetor - Exhaust Stinks!

[AutoInsane]

So.. this is not a question on a SuperCar or even a muscle car. It is on a muscle Jeep!

I have a 1974 Jeep CJ5: AMC 304 V8, Rebuilt engine, Edelbrock intake, MSD Ignition, Holley 650 4bbl, Patriot headers, stainless steel exhaust (no cats). The exhaust exits at the rear of the Jeep.

The carb was installed and tuned by a shop that does a lot of old school muscle and runs multiple race teams. The engine has tons of power and runs really well.

After driving the Jeep my sons and I reek of exhaust smell. My guess would be that it is running rich. When I asked the shop about the issue the response was that the carb is tuned correctly and the smell is what it is.

While it doesn’t quite make your eyes water, It is bad enough that I don’t want to even drive it.

My question is would y’all guess that it is not tuned correctly or with running a 4bbl the exhaust will have a bit of a noxious smell?

I have been thinking if I can’t get rid of the smell with the carb I will either go with Holley EFI but that won’t be cheap or if I installed some high flow catalytic converters.???

Please let me know if I need to provide any other details to figure things out.

Any thoughts are appreciated! Thanks!

[Mr. Chevy]

Are you certain there are no exhaust leaks anywhere? I had an older Jeep that did the same thing but it was due to an exhaust leak issue. I would maybe start looking there first. You could pull a spark plug to see how rich it may be running also.

Rich

[Locker537]

If the engine runs well, then I would not assume it is the carb. Is there any smoke coming out of the exhaust?

I agree I would start looking for an exhaust leak. How far does the exhaust extend at the rear? I wonder if it's simply getting sucked up and around?

[earntaz]

I have a 1974 Jeep CJ5: AMC 304 V8, Rebuilt engine, Edelbrock intake, MSD Ignition, Holley 650 4bbl, Patriot headers, stainless steel exhaust (no cats). The exhaust exits at the rear of the Jeep.

Sounds like the exhaust may be entering the back of the cab/vehicle ...suggest after the rear axle turn pipes 90 degrees to the outside ... exhaust will be pushed away from the rear ...

[AutoInsane]

No top on the Jeep, exhaust exits right at the back of the Jeep (no bumper so it is right at the end of the Jeep), I don’t think there are any leaks (I will check)

Is the noxious smell normal? I have been around carbureted cars at car shows and they don’t seem to stink like mine!!

Thank you all for the replies!!!

[SuperNovaSS]

It sounds like you are definitely getting exhaust in the cab/passenger area. Turndowns should help. You should be glad it sticks. If it didn’t, you would just get getting hit with carbon monoxide and wonder why you are tired and dizzy all the time. I agree with the above. Eliminate exhaust leak possibilities. If that does not do the trick then you will likely have to reconfigure the exhaust.

Jason

[Big Block Bill]

Just a thought, does this smell happen with all brands / grades of fuel? Some lead free fuels have a lot of ethanol in them which can be causing your smell. If you can, get some, (because you stated you do not have converters on it) leaded Racing fuel (like Cam-2) just to see if it makes any difference. If that does not change anything, then I would have to agree with everyone else that the exhaust exits needs to be modified. Good luck.

Bill

[olredalert]

[QUOTE=Big Block Bill;1497756]Just a thought, does this smell happen with all brands / grades of fuel? Some lead free fuels have a lot of ethanol in them which can be causing your smell. If you can, get some, (because you stated you do not have converters on it) leaded Racing fuel (like Cam-2) just to see if it makes any difference. If that does not change anything, then I would have to agree with everyone else that the exhaust exits needs to be modified. Good luck.

Bill[/QUOTE

----If you can find it try marine fuel. Its generally 90 octane if you can track it down and has no ethanol. If you can find it you may want to spike it with a couple of gallons of 110 to bring the octane up a notch or two......Bill S

[1971ls6]

Turn the idle mixture screws in 1/2 a turn and see if the smell is better, adjust the idle after. If it is rich, when you turn in the mixture screws, the idle will increase

[Big Block Bill]

I made my suggestion about trying a different Brand / Grade of fuel and possibly race gas assuming you had ruled out any vacuum leaks and the mixture was set correctly. Just holding your hand over the carb (trying to choke off the incoming air) while it is running can tell you if there is a vacuum leak or the mixture screws are not adjusted correctly if the RPM increases while you are doing that. Spraying carb cleaner around the carb base and intake gasket area can find a vacuum leak also if when you do the RPM increases.

An intake/vacuum leak can cause this smell you are talking about. Even if there is a vacuum leak it can run very well off idle. Once the engine is up to operating temperature, have you hooked up a vacuum gauge to manifold vacuum and adjusted each mixture screw until you have the highest vacuum reading and RPM? If not, that would be my first step.

I'm surely not questioning you're mechanical abilities but as I stated, I "Assumed" and we all know what that stands for. Just trying to help here.

As Snap On tools tag line went from years past, "Test, Don't Guess"

Let us know how you make out, Good Luck!

Bill

[SuperNovaSS]

Any updates on this? I’m curious about the outcome.

Jason

[Big Block Bill]

So......Anything to report? Inquiring minds need to know. You have us all wondering how you made out with your stink concerns or did you just decide to have kwhizz schedule it to install an LS Motor in it? Let us know.

Bill

[Big Block Bill]

Any reports on what you did to fix this issue? Let us know.

Bill

[Lynn]

l think this is the update.

https://www.yenko.net/forum/showthread.php?p=1551987#post1551987

[Big Block Bill]

Thanks Lynn, I must have missed it. That's one way to fix it (As long as it's not a vacuum leak from the intake manifold or such). I always thrived on diagnosing drivability or challenging issues. Thanks again Lynn for posting this.

Bill