401 smoking issue

[brentwood]

Hey guys, my 401 is smoking badly. It smokes a bit at idle and gets worse at higher rpm.
It's not burning oil or coolant. It starts right up, idles well at 950 rpm, runs strong and sounds good.
I readjusted air fuel mixture, made sure choke is opened all the way and double checked timing.
Everything seems fine besides excessive smoke, which is primarily coming from right side of exhaust.

What do you guys suspect the problem is?

[levelhead]

A faulty modulator valve on your transmission can cause your 401 to suck trans fluid through the vacuum line to it into the intake manifold and burn it. Pinch off or plug the vacuum line temporally (your trans won't shift ) and see it that stops it. If so replace your modulator valve.

[SC/397]

This might sound strange but check for a valve cover gasket leak first. If a valve cover is leaking and a exhaust manifold is leaking, the exhaust manifold or header will draw oil in to it and of out the tail pipe in smoke.

[Cliff]

I had a strange problem where my fuel tank vent line (the one that goes to the charcoal canister) had rusted closed, and on warm days the fuel was building pressure in the tank and pressurizing the fuel line to the carb and richening the mixture, and making tons of black smoke under acceleration. Since this is affecting one side more than the other I wouldn't suspect this, but thought I would throw it out there anyway.

[brentwood]

A faulty modulator valve on your transmission can cause your 401 to suck trans fluid through the vacuum line to it into the intake manifold and burn it. Pinch off or plug the vacuum line temporally (your trans won't shift ) and see it that stops it. If so replace your modulator valve.

Thanks, I'll check that next time I work on the truck.

[brentwood]

This might sound strange but check for a valve cover gasket leak first. If a valve cover is leaking and a exhaust manifold is leaking, the exhaust manifold or header will draw oil in to it and of out the tail pipe in smoke.

Not seeing a valve cover leak. Installed new gaskets a few months ago.
This reminds me that I plugged exhaust manifold emissions ports back in the summer. The driver side went smoothly. On the passenger side, pieces of inner tube came out with stock bolts. Could this be my issue?

[brentwood]

I had a strange problem where my fuel tank vent line (the one that goes to the charcoal canister) had rusted closed, and on warm days the fuel was building pressure in the tank and pressurizing the fuel line to the carb and richening the mixture, and making tons of black smoke under acceleration. Since this is affecting one side more than the other I wouldn't suspect this, but thought I would throw it out there anyway.

Thanks for your reply. I have a fuel pressure regulator set to 5psi.

[jammer1]

Could it be bad valve seals (letting oil into the cylinder). May be able to see it on the plugs.

[MysticRob]

...It's not burning oil or coolant...Everything seems fine besides excessive smoke, which is primarily coming from right side of exhaust.

I don't see where you've described what the smoke smells like.

You said it's not burning oil or coolant, but how did you verify that?

You also stated it's coming from the "right side of exhaust". Do you mean it's emanating from inside the engine bay or the right side exhaust pipe (assuming you have dual exhaust)?

Hard to help troubleshoot when we're not right there with you, but first I'd ensure you've properly identified the type of smoke (maybe you have, it's just not clear in your posts thus far), then work on identifying where exactly the issue is coming from.

[brentwood]

Could it be bad valve seals (letting oil into the cylinder). May be able to see it on the plugs.

I'll check, thanks

[brentwood]

I don't see where you've described what the smoke smells like.

You said it's not burning oil or coolant, but how did you verify that?

You also stated it's coming from the "right side of exhaust". Do you mean it's emanating from inside the engine bay or the right side exhaust pipe (assuming you have dual exhaust)?

Hard to help troubleshoot when we're not right there with you, but first I'd ensure you've properly identified the type of smoke (maybe you have, it's just not clear in your posts thus far), then work on identifying where exactly the issue is coming from.

My oil and coolant levels aren't noticeably dropping. Smoke doesn't smell like coolant.

Yes straight dual exhaust, no x or H pipe.

Drivers side has "normal" amount of exhaust smoke.
Passenger side has excessive smoke that gets worse as engine warms up and at higher rpms.
Smoke comes from passenger side tailpipe and back of engine bay/front of cab area on passenger.
It's not safe to drive, the fumes are getting into the cab.
I have to spend some time looking at it and I'll update the post if I find anything.

[MysticRob]

My oil and coolant levels aren't noticeably dropping. Smoke doesn't smell like coolant.

Yes straight dual exhaust, no x or H pipe.

Drivers side has "normal" amount of exhaust smoke.
Passenger side has excessive smoke that gets worse as engine warms up and at higher rpms.
Smoke comes from passenger side tailpipe and back of engine bay/front of cab area on passenger.
It's not safe to drive, the fumes are getting into the cab.
I have to spend some time looking at it and I'll update the post if I find anything.

That helps narrow it down. If not smelling of coolant, it also won't be carb related since the effect would be seen out both pipes, so it has to be something related to that passenger side.
Does it smell like unburned gas or oil? You didn't mention that either.

I'll assume oil since you didn't mentioned it misfiring from a bad plug or lack or spark on that side, so maybe the valve seals as jammer said, gummed up rings not sealing a cylinder properly, or something else along those lines.

I had gummed up rings on my high mileage Saturn 4-banger. I poured Seafoam into the crank to loosen all the sludge and deposits, ran that for quite a few miles, and that eliminated the problem for me. Hopefully your plugs give you more info.

[wiley-moeracing]

Are you getting a lot of blow by out of the vents?, If your getting more smoke when warmed up I would look at valve guide seals, the umbrella type get hard and break off with age, viton seals are better but require machining of the head.

[brentwood]

I tried seafoam in fuel and crankcase oil last week. Also used a bottle of the seafoam for carb/intake.
I ran it for a couple hours since. Can't drive it because it smokes too much.
The smoke is a light grey whitish color.
I pulled passenger side spark plugs... No oil on plugs but they did have a lot of soot/carbon on them.
I tried pinching off trans modulator line...made no difference.
Still no noticeable oil or coolant loss.
I really don't know what to do and can't afford an engine rebuild right now. I may just end up selling it.

[Heep-J4000]

Maybe not a question that makes sense , but how is the brake fluid level in reservoir?

Maybe doing a compression test also to rule out all possibilities!?