Hello, all ~
I could use some help figuring-out a strange occurrence.
We have a couple of long sweeping off-ramps here on I-5 in Seattle.
Whenever I come through those a bit hot, I leave a huge plume of smoke behind me. Some are right turns, some are left turns. Happens on both.
The motor doesn’t burn oil. Doesn’t smoke, never at start up nor while driving spirited.
It only happens on these sweeping curved ramps.
I can see a bit of an oil trace on the pass-side PCV-valve, which is an aftermarket one, but that’s it.

Might anyone have a theory what causes this condition …?

 

Does the smoke occur while your are accelerating or decelerating? Are you losing any ATF? Pull the vacuum hose of at the transmission modulator, there shouldn't be any ATF in the line at all.

Any chance of a plugged oil return in a head? Is the engine fresh? It looks great!

Is the aftermarket PCV valve application specific to the Olds 425? I've seen incorrect PCV valves cause oil usage.

 

The oil smoke does not seem to have anything to do with accelerating or deceleration, only when sideway gravity is in play, like during sweeping curves at a good clip.
The engine is original. Never been opened up.
The original PCV valve rubber elbow cracked recently, so I put a generic one on it instead, until I find an OEM one.
There is a bit of an oil trace around that area, but not enough to be causing a massive plume of smoke.

Thanks for trying to help me figure it out …

 

Replace the valve stem seals. Should clear it up.

 

Unless I am looking at something totally wrong I see a breather on the passenger side valve cover and maybe a pcv valve on the drivers side ? Pull the hose off that goes from the drivers side valve cover to the bottom of the carburetor and see if there is any oil in it.

 

Once had a 66 Dynamic 88 with a 425,, on the highway at 65+ mph lots of white smoke could be seen in the rear view mirror. If I slowed a bit it would stop. Turns out something was wrong in the trans and at speed fluid was being pumped out of the trans dipstick tube and onto the exhaust. Maybe you have something similar where trans fluid is the issue? Just a thought.

 

If the motor has never been opened up and is original, the rubber umbrella valve stem seals have most probably started to break apart from age and as you power into a turn oil in the upper cylinder head is pulled across the valve stems and is causing that. Replace the old rubber valve stem seals with the newer nylon type.

 

Thank you all for your advice. I certainly have some areas to troubleshoot now 👍

Tom

 

What color is the smoke, by the way? We are all assuming that it is oil smoke, but it could be something else.

 

Could someone follow you to see if the smoke is coming out of the tailpipes to eliminate a spillage burning off a manifold etc.?

 

Smoke looks white to me. A couple of times the oils pressure light briefly came on, which makes me believe it’s oil-related.
The worn valve stem seal theory makes the most sense to me, where oil is pushed into the heads during higher g-force sweeping turns.
But shouldn’t I also see a puff of smoke at startup then, too …?

 

 

White is likely ATF or coolant. Yes, valve seals usually give a puff of bluish smoke on start up.

 

Extremely beautiful car!!!
I've never seen a 66 (A code) in black before.
I've often said before I leave the planet I want a Dubonnet (U code) maroon 66 like Dad had. I guess I'll need to add black to that bucket list.

The valve seals can be changed without pulling the heads.
Pump cylinders with compressed air, compress the valve spring, and remove the retainer...R&R seal. reverse procedure.
Always a good idea to bring each piston up to TDC just in case something goes wrong you don't drop a valve.

 

You can also bring the piston to TDC, remove the spark plug and insert as much common rope into the combustion chamber as possible to keep the valve from dropping down as you change the seal. The new seal will be tight going on and will locate itself on the valve stem once you start the engine so when installing the new seal just push it down as far as possible on the valve stem. Some seal kits may come with an installation tool or you can use a deep well socket, tapping on it with a hammer to start the seal onto the valve stem.

 

Thank you all - very helpful🤞

Tom

 

Have someone else drive behind you when it happens. They will be able to see if it's white or blue better than you can via your rear view mirror. Another symptom of worn or missing seals is that when driving at highway speeds for say 15 minutes with the engine fully warm. Abruptly take your foot of the gas, it will let out a puff of blue smoke.