VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 excess smoke

I have a 1931 Chevrolet 5 window coupe. I inherited the car from my father and believe that it was completely restored. When it runs for any period of time the vents on top of the valve cover send out a lot of smoke. It has the orginal style oil pump. Is this normal?

A small amount of smoke (oil vapor) from the valve cover vents is normal but a lot of smoke is not. If the rocker shafts/bushings are worn then extra oil will be dumped onto the head increasing the amount of smoke. If the valve cover gasket leaks then hot oil can contact the manifold increasing the smoke.

The oil pump type will not have any effect as only the rocker shafts are lubricated. Lots of smoke out of the crankcase vent indicates more of a problem.

Or no smoke out of the crankcase vent (road draft tube) indicates the vent is plugged-up with sludge and all the "fumes" are exiting through the valve cover vents.

When driving at speed fresh incoming air actually enters through the vents and the fumes are drawn out throught the road draft tube.

Thank you for the information. It is hard for me to know what is too much but the last time I ran the car there was some smoke that was visible coming from under the hood when it was closed. I suspect that is too much.

Yep, that is definitely too much smoke.

If the car gets limited use or it sat for a long time it is possible the rings are 'frozen', causing the smoking. A light oil such as Marvel Mystery Oil (added to your oil) can frequently help un-stick rings. Just today my neighbor was cursing his lawn mower for poor running and smoking severely. We cleaned out a mouse nest, cleaned the carb and added MMO to the oil. After several minutes the severe smoking stopped and the mower runs great.

The car had not been started for a decade at least when I loaded and took it to a mechanic to get it started. I will try your suggestion because I have run it less than 3 hours total since that time.

Thank you

Please let us know how you make out with the fix.

The Marvel Mystery oil in the motor oil may make for more smoke as it is partly solvent and will burn-off when oil is fully hot. This indiactes that it is "working"

Gene,
When we first started the mower every mosquito for 50 miles was either dead or wishing they were! My neighbor thought for sure we had killed the engine, but after a few minutes the cloud blew away and bit by bit the engine ran with less and less smoke. After 5 minutes it ran 'good as new'.

I will be trying Marvel Mystery Oil in the next couple of days. I will report the results to all of you. I thank you so much for your interest and help. I am just getting to know my car and haven't been able to find anyone locally who can give me advice. This site is amazing and very helpful.

We're glad you have found us to be helpful. I looked at your profile and it appears you are not a member of VCCA. You may want to consider investing $35 per year to be member and receive our monthly magazine. It has all sorts of tour, show, technical and classified info you will find invaluable. Being a VCCA member also allows access to 'members only' pages on this website.
Membership info can be found in a link on the main website page.

Yesterday, I started my car after putting some Marvel Mystery in both the oil and gas. I ran the car until the temperature came into the normal range. There was no smoke at all. I did not drive the car but just let it idle. I am not quite sure what is happening. On another note, I have sent off my application to join VCCA. Thank you for the recommendation.

As soon as you receive your membership card your car will run perfect and no smoke.

I knew VCCA membership was great but just not that GREAT. Come to think of it my engines don't smoke either. Now I know why.

That's good news times 2! The car is better and you'll be a member of the world's greatest Chevy club!

What happened with the MMO is that it probably disolved the gunk that formed when gasoline, carbon and oils mix. The result is a black deposit that makes moving parts stick together. It sounds like your piston rings were stuck and that allows oil to get sucked into the combustion chamber thereby causing the oil smoke. The MMO frees us the stuck parts and the rings are able to expand to conform to the diameter of the cylinder and keep the oil where it belongs.

The next step will be to change the oil in the car. You now have a lot of slimy sludge in the oil pan that should be removed. It may take several frequent oil changes (with a good detergent oil) to clean the inside of the engine. Keep an eye on the oil pressure when driving...if too much sludge is drawn into the oil pump screen you can have restricted oil flow which is not a good thing. You may have to drop the oil pan and clean the screen (there is no oil filter).

MMO is also useful if you store the car for the winter. Add it to the oil and gas before storing. Chevgene also recommends when prepping the car for winter storage to add it directly to the carb until it stalls. It coats all the key pieces and makes it easier to restart when the weather warms up.

Welcome aboard!