I have a 69 vert 350. I don't know if the cause of my overcoming exhaust smell is:

1) It's just a convertible and that is the nature of the beast
2) my exhaust is leaking somewhere
3) It's getting in through the firewall

The floors have been redone, but it is bad. Today, I got stuck in stop and go traffic and I really thought I was going to get carbon monoxide poisoning. It is worse when the car is stopped. But even at highway speeds, something does not smell clean. I would expect fresh air with the top down.

And ideas?

I'd say door # 2...

I do know coupes seem to have this issue, so I think its a bit common. I have the top down 98% of the time with my 'verts, so I don't notice it in those.

Maybe your real lean on your car adjustments? If it is burning real rich it has bad fuel odor too. Is your breather on the valve piped back into your air cleaner? unburned fumes smell.

Just thinking of other items.

If I recall, I moved the idle mixture until the engine stumbled and the backed off either a half or quarter turn (according to Chilton's).

But twice in the last two weeks, I have noticed a black chalky substance directly behind the right tailpipe on the concrete. It looked like soot. Over-rich?

Sounds like it. Sometimes we can not go by the manual today on the adjustments because the gas is not the same today.

I'm not a good source on adjustments but I know we don't want a bunch of fuel fumes reaching the exhaust, That just means your wasting fuel. We want it burned before getting in the exhaust.

Sometimes the carb goes bad and can allow you to run real rich.

Do you have the original quadrajet on?
I ask because the well plugs on those almost always leak which will end up giving you a very rich idle.

If you know how to use a vacuum gage, I'm pretty sure its ported vacuum and you adjust each screw to maximize the vacuum reading. 1/2 turn at a time and let the car recover. Higher number is better. I'm sure someone can chime in with better details.

It is a 2 barrel rochester.

That would be interesting to know, hopefully someone can chime in and give a play by play on how to set the carb with a vacum gage!

I'd say door number two as well, but.

It's manifold vacuum where you want the gauge. Keep adjusting the idle mixture and the idle speed until you get the highest vacuum at the correct idle rpm.

Is it a stock engine or did you put in a cam with a bunch of overlap and high duration?

If you have the timing retarded it can fire the fuel charge late, which can lead to the charge burning as it's going out of the port rather than in the cylinder. But the soot behind the exhaust pipe sounds like it's burning too rich. I wouldn't think it's the idle mixture though if it is stinking at highway speed.
Maybe a sticky or sinking float?

Thanks BlueBird, I had never heard of setting it with Vac on the port, but with Man vac, so I thought I was missing something and glad you heard the same thing!!!

Mine stinks too, especially when I'm running it in the garage and the whole house gets stunk up (the wife loves that). I think it has to do with the modern 93 octane gas without a catalytic converter.

I feel your pain Bob, I catch hell and have to open the garge door and the door leading outside in the garage to expel the smell...lol

That's not "stink". That's nostalgia.

Well, sometimes it's not the gas or the timing or the carb idle adjustments, but the engine components.
Joe blow wants to have a 532 HP engine. He reads all the literature and determined he needs an X camshaft and a B intake manifold and a F carb to get the 532HP. After all if the magazine says they can do this for $534 in parts then 'why can't I?' After boring the cylinders and buying the hot pistons, intake manifold, carb, cam, and heads he has an engine that gets 532 hp on the dyno. Man is he happy!
Then he puts it in his Pontiac and it runs like crap, stinks like hell and gets 4 miles per gallon. All the drilling of holes in the carb plates and timing adjustments in the world do nothing to stop the smell. WTF?
He has an intake manifold that is rated from 2000 rpm to 7000 rpm a camshaft that comes online at 3300 RPM, and a carb that will support a 1127 CID tractor puller.
Joe drives the car to the local A&W at 34MPH. Everyone around him puts on safety glasses and a respirator. Joe can't figure out why, after all he got all the latest RACE parts.
I have a friend who suffered with stinky exhaust for ages, but for some reason wouldn't entertain the thought it may br the parts not the adjustment that was the problem.

I'm sorry, was I ranting?

Manifold vacuum is the vacuum below the throttle plates, the vacuum reading one has whether the throttle is open or closed. Ported or timed vacuum is just above the throttle plate, none until the throttle is opened. No, or little, vacuum sense at idle and total vacuum sense with the throttle open. We adjust idle mixture with the throttle closed so we need to have the guage connected to manifold vacuum.

But I could be wrong, happens all the time.

x2 I sent my final adjustments with vac gauge as well.
Stink? You got a monster with the power of 3 - 2013 trucks under your hood with no smog control. You going to have to break a few eggs to make an omelette. lol

Sry Gus, not sure what you meant by that but I have a stock 69 400, so figured a carb not adjusted right or I am just totally missing your comment...?

How about #2 Jack your car up and check for leaks. Muffler shop should check it for free.

Well if you don't crack the eggs they roll around in the pan.

How's your vacuum advance working? If it's hooped you could be running with late timing and not knowing it, just the initial and mechanical.

When I finally got my 428 put back together I set the timing to 29 degrees [best power on the dyno]that gave me only nine degrees initial. The thing ran very hot at idle and made my clothes stink. I put on a new vacuum advance can and connected it to manifold vacuum rather than stepped. It ran cooler and the stinky exhaust quit. You would have yours set higher than that though. Just a thought.

Man, I skipped the most obvious, it your choke working correctly?
Sticky choke=rich burn.

Wow! Bad news... I was checking for fumes in the engine compartment and saw a little smoke coming from the manifold. But it was oil from above. Don't know if it is the cause, but it led me to a horrific discovery. Since I saw some oil staining above manifold, I figured I would check the oil level since it may be a little low. A little would be an understatement! It was 3 quarts low from just 1200 miles of driving. And there is no 3 quart oil stain on the concrete. The oil was just dark. Did not look creamy. I will check the coolant for oil. I wonder if it could just be oil leaking past the rings that burned almost 3 quarts of oil. :-(

That's a lot of oil gone. Is it leaking out of the rocker cover and burning on the exhaust? Three quarts burned while driving would be a real stinker at that.

There is some oil that has come out below the valve cover.

Also, I usually only see visible smoke coming out of the tailpipe on startup and when I rev the engine. Not when I am cruising or idling. The smoke is whitish greyish.

This sounds all to familiar to me.

I have gone through the stinky exhaust and the valve cover leak as well as many other leaks with my bird.

Best advice I got for the valve covers was silicon the gaskets to the covers and lay them flat on a counter to dry. Then when installing them finger tight and all the way around then another 1/4 turn, no more then that. I did my last set that way and it worked great, no leaks at all. That burnt oil on the exhaust was really bad, would burn my eyes.

With the stinky exhaust, I had a 110 lsa ultradyn cam that had some low manifold vacuum. Around 10 to 11. Not really low but had nozzle drip bad in my Cliff Q-jet. Only had to fire it up for a second in the garage to stink the whole house up and my clothes. I went with a roller cam on a 114 LSA and now have a smooth idle and 14-16 vacuum, not to mention much more power. I also had my heads done at the same time. My plugs were all ways getting gummed up. I had those crappy umbrella shields on the valves and my engine builder mentioned they just pump oil into the valve stem. They were replaced with Viton seals and its a night day difference.

I still have a little stink to the exhaust but nothing like I had before. I hope to get a A/F gauge and tune it a bit better and see if that helps.