VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 33 coupe belching soot

My 33 has begun to blow black smoke while idling and under acceleration blows smoke like a diesel. Naturally I am also fouling plugs. Can I adjust the fuel mixture on the carb to get the car to run leaner, or do I simply need to rebuild the carb?

If this a recent occurrence, it could mean something broke. Otherwise it may be the rings. A simple test is to warm the engine up to operating temperature and slowly dribble some transmission fluid down the carburetor while keeping the engine running. You will get an enormous cloud of smoke, so warn the neighbors not to call 911.

Next step is to check the float in the carb and see if it has sunk.

Keep us posted.

Well it may be more serious than I thought. I figured if it was bluish smoke it would be the rings. I will run the test you suggest. The car runs pretty smoothly but seems to be lacking power and compression. I am about to run a compression test. What should I see, about 90lbs per cylinder?

First thing I would check is the float. It may be filling with gasoline and therefore causing a rich condition. Next is the needle and seat. If not sealing properly will overfill the float bowl and cause engine to carbon up.

I just pulled each plug and ran a compression test on each cylinder. All my brand new plugs are black with carbon-the plugs are dry-no oil. Each cylinder did not show a reading. All were 0 lbs. That seems odd because the car starts just fine and runs fine albeit maybe not as powerful and quick to get up to speed as I think it should. Chipper I will check the carb, but now I am concerned I am showing no compression. With the way car runs I should get a reading on my compression gauge. I may have a leak in the gauge. With the condition of the plugs it seems to be the carb. I will check back when I run Chippers tests.

Check to be sure the air cleaner is not plugged. Little air and lots of fuel have the same results.

Your compression gauge may have a problem.

Chipper the flat bowl is half full.

Did you check the float to see if it is full of gas?

The float has no fuel in it, just the float bowl. The float appears to be fine-no cracks or holes. I did notice the air filter is not letting much light in so that definitely was overlooked and needs replacing. So as Steve D suggested can it simply just be the clogged air filter?

Try to run it with the air cleaner on and then off. That will check the air cleaner. Put your thumb over a spark plug hole and push as hard as you can. If your thumb is blown off the plug hole when the engine is cranked over you have decent compression. If the exhaust system is partially plugged it will also cause a rich combustion condition.

Just ran car with air cleaner off. Very dark black smoke when I punch accelerator. I think you are onto something with the exhaust. I have noticed the exhaust has suddenly gotten loud. The car sat for about a year and was not driven much so the muffler could have rusted out from lack of use and gotten clogged. Guess I can piss off the neighbors and run the car without the muffler to see how black the exhaust is. There is likely lots of carbon to be blown out of the engine so the exhaust will be black for a while. I will pull off the muffler and shake it to see if the insides have broken down.

Remove ALL spark plugs, before doing compression test.

hi there,
reading all the posts made me think of the very obvious............is the choke knob puled out and needs to be pushed in?
simple solution but so obvious that no one else posted it?
I had the same problem with my ride on mower, running roughly and I had forgot to move the choke to RUN position....such is life and getting older ..

Peter

Black smoke generally indicates excess fuel, blue smoke indicates oil and white smoke (steam) indicates water (often seen in cold humid weather).

Generally engines are hard to start with less the 60lb compression on at least 4 cylinders. I look for at least 80lb in all and preferably 100lb + with no more than 15lb variation between least to most.
A squirt of oil in each cylinder and retest, big difference indicates rings worn and little difference indicates problem above the head gasket. With this in mind I would think JYD is right, your compression guage is not working correctly.

Tony

Car starts easily and with a loosely fit high performance muffler, still blowing tons of black smoke. Took loose fit pipes and muffler off and inside of pipes are black as coal. Will run compression test next. Car starts easily but has no power.

Still betting on a sinking float (float filled with gasoline) or a needle and seat problem.

Do you have experience with rebuilding the carb ?

Not a carb guy. I might just ask Doyle Stokes to send me a rebuilt exchange. He sent me a rebuilt for my 34 sedan. Ran great. I sure hope it is nothing more serious than the carb.

Thanks much

Let us know what you find when you do your compression test.

Have you added ANYTHING to the gas? No need for additives, substitutes or oil of any kind with todays gas. If nothing additional in the tank then your mixture is too rich, change carburetor and if the proble still exists then you probably have a loose valve stem or worn-out passage(s).

Carbs are not really that complicated. If you say the float has no leaks, how did you test the float? Shake it? That might be ok if there is enough fuel in it to shake. Otherwise heat some water in a pan to almost boiling, no bubbles in the pan. Dip the float in the hot water and look for bubbles coming out of the float. If all is ok, have you checked float level? Does the float have the metal needle and seat or the flat rubber plunger "needle" and seat? They have two different height specs. Even before you disassemble the carb, look down the carb while the engine is running at idle and look for fuel dripping from the boost venturi. That indicates a fuel level problem, either float, height, or needle and seat. Too high a fuel level will cause dripping. Needle and seat work may be in the offing.

My neighbor is a prime example, as danger working with carburetors. He was attempting to pore some fuel in the carb in order to start it. It backfired, caused him to fall and spill all the fuel on his face and upper body. He spent several days in a burn center just to save his life. He is fairly well healed now with scars all over his head and chest and shoulders. No ears, some nose, badly scarred chest.

Even to look down in a carb to check the action of the accelerator pump, you should have a plastic shield. Better yet, use a mirror and set up a 90 degree line of view.

Didn't mean to disrupt this thread, but that needed to be said.

Loss of Power-- causes

1. Loss of compression -- test with compression gauge. 90 to 70 pounds good. If one cyclender is low and the rest have a close range then the low one is your problem. Could be a blown head gasket.

2. Too rich mixture because of some defect in carburetor. Did you look for "grit" in the bowl under the float valve?

3. Late ignition timing. Use a tming light. Check the "ball" on the fly wheel in the square hole. See where the needle is pointing to the "ball" when the timing light flashes.

Due to work and family obligations, it has been a while, but I wanted to provide an update of my problem. I sent my carb to Doyle Stokes and he sent me a replacement. He said he needed time to rebuild mine which he said was a mess, likely from contaminated fuel. A new gas tank for this 33 is $875 as it apparently has a unique gas filler neck. So rather than buy a new one, I removed, flushed, rust proofed and sealed my tank. I also flushed the fuel line to the pump. I will get the tank back in the car hopefully this weekend. I just did a compression check with a new compression gauge and a cold engine. I got a consistent reading of 70 pounds in every cylinder. Not sure, but I guess that is acceptable for an original engine with 82,000 miles.

I will replace the carbon black spark plugs, add a new fuel filter, cleaned air filter, and new muffler, and pray the problem was the carb. The muffler was broken down inside so I am sure it was not helping matters.

As soon as I get it all together, I will advise the result. Again thanks to all for your assistance. If anyone has an opinion on my 70 pounds of cylinder compression, I would like to hear it. Seems a bit low to me as I was expecting 90 pounds.

Best regards,
Jolo

Just checked the TANKS INC website and they do not make a gas tank for either the 1933 Chevrolet standard series or the 1933 chevrolet master series .

Very surprised !

mike lynch