This is probably a question that's come up a million times on this site. My 69 cutlass 350 has an extremely strong pungent exhaust odor. So much so that other cars following behind me drop back to avoid the fumes. The engine burns no oil, has no smoke and good compression. I installed a new edelbrock 4 barrel to no avail. My mechanic buddy tells me they all smelled like that back in the day but I don't recall it this strong. Im thinking it could be ethanol gas. Any suggestions?

 

Air fuel mixture could need some adjustment... I recently made some adjustments in this department myself.

https://classicoldsmobile.com/forums...ds-etc-187428/

He's right... We are getting old and the younger generations have had a continuous string of decades of less and less exhaust smell. At the same time we old schoolers have been conditioned to modern exhaust traits as well. Plus the issues with the quality of modern gas running through our cars antiquated system. That's why I have gone with high flow cats on my ride. Makes a world of difference, I can eat while standing behind my running car now if need be. I wouldn't of dared pre cats. Also cars stay behind me now, versus backing off or eventually switching lanes when there is no other apparent reason to do so.

 

When I got my 75 Hurst Olds the catalytic converter and the single exhaust were long gone. After I had changed the muffler to Super Turbos, I installed two high-flow cat converters. Smell is gone.

 

Glenn, that's great, but OP's car was never equipped with cats from the factory so it's not likely he has that classic '70s sulfur "rotten egg" smell.

@Blafau , can you describe what your car's exhaust smells like?

 

👍

And I bet she is quicker than new Red.

​​​​​​Blafau, high flow cats have a 1/4 of a regular cats honeycomb cell count. So it doesn't hinder performance, while still getting the job done. I'm on my 3rd set in 10 years, mainly because I was testing performance at the track. Flowmasters, Magnaflow, and back to Flowmaster. 0 negative effect in all out performance. Tested dozens of times in various tracks and various conditions.

Magnaflow was pricier and not worth it in my opinion. Flowmasters are perfect but the price has doubled since I first had them installed.


They were 1/2 that when I first got them. Then around 75 the last time. So they are creeping up but still well worth it in my opinion. Good solid quality piece.

And as you can tell by my short video clips she still sounds angry as ever. (But there is a slightly lessened audible tinge in aggression.) Still a win win in my book.

 

This is all well and good but @Blafau 's car DOES NOT HAVE a cat unless somebody retrofitted one. Absent that exception, the explanation for the odor must lie elsewhere.

 

When our cars run rich, the smell increases. Decades of people "improving" their cars by changing jets and carburetors is often the reason.

Find someone with a lambda meter to test your car and change jets. Your gas mileage will increase as well. This can be done on a chassis dyno.

Smell at idle can be reduced by turning in the idle jets until the idle speed decreases by about 100 rpm, then readjust the idle speed screw back to spec. Be careful that there is no missing, otherwise the smell will be back again.

 

The idle AF mixture screws do nothing for the rich condition once off the idle circuit. I would check the ignition timing, retarded timing will cause it to smell pig rich.

 

No, is is not the ethanol gas. All we have here in Phoenix for the past 2+ decades is 10% ethanol fuel, and it does not produce the smell you are experiencing. My car has undergone and passed emissions testing for years running E-10 fuel. You likely have an overly rich air/fuel mixture. Did you re-jet and tune the new Edelbrock carburetor?

 

For a really quick reference, look in your tailpipe(s). Are they tan, black or really sooty black? If black, you’re running rich, if sooty black, you’re really running rich and adjustments must be made.

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As mentioned, make the investment in a A/F gauge, then hit you tube on tuning your carb. It will likely improve power, drivability and the smell.

Also as mentioned, don't tune the carb until ignition timing is right.

 

Meh, you can tell whan a vehicle has had the cats hollowed out of removed, even on new cars. The gas stinks. There has to be something in the fuel that causes this. These are 2023 mustangs and vettes/etc that they are not going to be running rich.
I'd not be shocked if they add something so the popo can tell you removed the cat.
My B body with a 2023 Chevy Camaro lt4 v8 when running. pump gas it stinks. Sonoco 100 octane . no stink , it smells a little but not like the 93 pump 10% alky mix.

 

I'll second that as timing is easy to check although probably not the direct cause. Timing first then carb.

 

Checking timing with a dial back gun is all of 15 minutes. Not just at idle, I'd check it through 3K and get some idea of it's curve. I never touched an Olds 350 but with a SB Chevy, vac advance disconnected and the vac port on the carb plugged you're looking for 34-36 degrees max @ about 3000 RPM.

I'd be looking for vacuum leaks too which are extremely common. If I don't find a cracked or unplugged hose I usually shoot carb spray around the base of the carb and intake and if you hear the idle increase you found the leak.

You can set the base fuel/air mix by ear but I use a gauge. They might be available as loaners from one of the chain Auto Parts stores