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

Starting black smoking after a coil replacement highly suggests an ignition problem and not rings or other mechanical malady. That does not mean it can not be a coincidental failure. Just going with odds. Making a change that results in a new observation is more likely due to the change.

The black smoke indicates too much gas being burned AND BEING BLOWN INTO THE OIL. The thinned out oil could cause excessive blow-by.

Black smoke is unburned carbon from incomplete combustion. Either too high fuel to air ratio or lack of enough "spark" energy to have burn rate fast enough to combust everything before the pressure reduction stops the burning. Though most often too much fuel it can be due to timing and/or weak spark at the plugs. Because of the design of the combustion chamber in the head a strong spark is necessary in the early 6 cylinder engines.

I guess it is still running rich. I will go through the ignition again. Seems I should also try another new coil. I believe I have a spare. I put Castrol GTX 10w 40 high mileage oil in and it does seem awfully thin to begin with. Notwithstanding I may have gas in the oil, once I sort out the running rich issue, what grade oil do you suggest? Can I use a 20w 50? I have seen on these posts that 10w 30 non synthetic is the recommended grade. I am in a hot climate-South Carolina.

I will also reset the timing and put the Octane selector to +8 and see how it starts and runs.

10W-30 is what I use in all my old Chevys. I live in as hot a climate as SC. DO NOT use too high a viscosity oil as it will not properly lubricate the cylinder walls and wrist pins. They are lubricated with an oil mist generated when the dipper passes through the trough. Some of that mist also helps lubricate the rod bearings.

If you crank over the engine with the ignition on, spark plug removed (wire still attached) but grounded against the block should be able to determine if you have a strong spark at the plugs. It should be bright and make a "snap" sound. If tested at the coil the spark should jump a 1/2" gap and also make a "snap". While you have the plug out is it black? Should be if you are getting black smoke from tail pipe. Clean them all before putting back. Also check the gap. Should be between 0.025-0.040". Many of us prefer the wider gap as it produces a hotter spark at the plug.

Very helpful. Thanks.

I have good spark at all plugs. I installed brand new plugs gapped at 0.040. Car started easily. I ran it for two minutes then pulled the number 1 plug and it was already black. Even with the rebuilt carb, the engine is running rich. The car ran ok but has a miss. I did not get it to running temp. I am thinking this is a compression issue. I got cold readings of 70 lbs in all cylinders but with 12 volts. So the true reading would likely a bit less than 70 with 6 volts. Unless the rebuilt carb is defective, I think I potentially have bad rings? I adjusted the idle mixture screw on the carb 3/4 from closed then adjusted from there to even out the idle. With the mechanical fuel pump, I doubt I have too much fuel pressure.

I highly suspect the "rebuilt" carburetor. Those engines will run fine with 70 psig cylinder pressure. Are you sure that the metering rod and throttle plate are coordinated? Was it set with the proper gauge? Is the float properly set?

Also, does the "rebuilt" carburetor have all of the correct parts for that particular model of carburetor?

Thanks for the quick responses. I am not sure about the carb. I will contact the rebuilder today. If no luck there, I am willing to try another carb from someone else.

Here is a simple test I learned from an old time mechanic I
apprenticed for when I was about 15 years old! Probably not the most sanitary, but it works! Remove the brass fitting from
between the fuel line and the carburetor; wash and rinse the
fitting with hot soapy water, then rinse with cold water. Now, remove the carburetor and turn it upside down to drain all the gas. Re-install the 'now clean' brass fitting. With the carburetor in it upright (normal) position, blow through
the fitting; air should go freely since now the float has dropped and the needle and seat are open! Next, turn the carb
upside-down, and repeat! Now, the float should have fallen down and closed the needle and seat! You should not be able to
blow through there at all! If you can still blow air under these circumstances, either the float is stuck, or the needle
and seat is leaking! From everything I have read on this post,
I am convinced the problem is carburetion. I hope you have made sure the choke is open, and tried running the engine with
the air-cleaner removed!

Smoke comming from the valve cover after shut down is normal. I would think that doing a compression test would show a low reading on a bad ring. You will have to Re-test each cyclender again to make sure one of the rings did not blow out during your starting. If it was my car, I would have put oil in the cyclenders before starting after setting a long time. Some rust could have been there from an open valve on the cyclender wall. This rust could possably have caused a ring or rings to fail before getting lubrication during start up. TO PROVE IT IS NOT A BROKE RING...Removeing the plug and place compression gauge. Take reading, If low, put oil with a oil can into the cyclender in question; replace compression gauge and see if the reading comes up. If comes up...bad ring.(Note: some people who know the engine will be in storage for a long time place oil into the cyclenders to save the rings on re-start. The engine will smoke a lot upon start up until the oil burns out. Also rings have to "seat" and will make smoke until seating is finished. Set Timing with selector on "0". Then move Selector to improve starting and gas milage.)

Octane Selector: Make sure the slide under the Selector is well oiled and free to move. Set the Selector on 8 or 10 Advance for the regular, non-ethonal gas of today. It has 85 to 89 octane in it. 10 is the max Advance on the Selector. On my car that is towards the fender (advance or +).

If it was my car I would re-test each cyclender.

I think I can finally shut down this very long thread. I spent a few hours on the car this morning. I just took it out for the first time and it ran well albeit only at 25 miles per hour; I did not take it out on the highway yet. When Junkyard Dog and Chipper kept pointing at the carb as the problem, I figured I must have it set up wrong. So I started all over and set the idle mixture as lean as I could and have the car run smoothly, set the idle speed then reset the timing (it was off slightly) and the car suddenly started running well. I cleaned all the new plugs and pulled one out after running for a while-no black on the electrodes. So I think I am there finally. I want to thank all the valuable input from everyone and I hope other backyard hackers like me can benefit from this novel. To sum up, I had multiple issues-a bad carb and a bad Petronix electronic ignition. I am back to way the car should be; with the points and condenser. The only non original things are 12 volts and a new fuel sender and auxiliary fuel gauge.

Now if I can only get where I am going without overheating. Thanks again to everyone that contributed to my success.

JOLO.........its nice to see somebody who has been helped with info from fellow hobbists come back and actually say thank you.....

a rare occurance

mike lynch

Don't know how bad the overheating issue is but just because the water blows out the radiator cap doesn't mean it's overheating. My '34 runs fine with the water about two inches below the top of the radiator.

Hi Ron
I was idling a long time in the driveway and the temp gauge rose above 200. The car is due for a radiator flush (lots of rust under my Eagle radiator cap) and my water pump is leaking slowly, so I will flush the radiator and replace the water pump and thermostat and see if that solves the problem. Idling for long periods is not helpful and it was hot down here in Hilton Head yesterday. If that does not work, I will take the advice from a G&D article and install a Chevy Truck fan. My last resort will be an electric fan, but my luck has not been good introducing modern solutions to my car. The closer to stock, the better.

Thanks Ron

the stock 4 blade low pitched rad fan just cannot move enough air at idle.

IN a large long thread in this section where-in MILLN PHIL did the tests on the truck fan on his 35 std coupe. His results were proven successful . I believe the truck fan has a pitch angle of 28 degrees and draws more air thru the radiator.

Find it and read it .

Its not always a whole lot of backward flushing and boiling out.
Fins need to be tight to the tubes.
Tubes need to be clean.
Water pumps need to tight with no leaks.
thermostats need to be 180 and operating properly.
engine timing must be set to stock specs.
plus no leaking cylinder head gasket


mike lynch.............

Thank you Mike, very helpful

I am Phil, the guy who wrote the'Truck fan blade article. If
you look at my story again, you will see that I discovered it
was an flow problem by placing and electric fan about two feet
in front the radiator and watching the temp gauge while the
engine was still idling. When I did that, and before doing anything else, the additional air flow through the radiator
dropped the temperature about 20 Degrees! The larger fan blade
did the trick for me, and I have heard from several people with similar experience! Good luck, and let me know how it works out!

Pay attention to what Phil has said about the fan. Also, If the engine sat without water (dry) for a long time there will be "sheet rust" that has broken off and is stuck on the "head gasket" holes blocking water flow into the head. I have tried flushing and other products without success. The only way that I have be able to solve this overheating issue is to remove the head. Use a wire in all holes to losen all rust. Blow out with compressed air. Do the block too. That stoped the overheating. She runs nice and cool now.

Funny how we know the right thing to do but walk around it until we're forced to do it right way.

What you are risking by running hot is a broken head or cracked block. Replacing a head gasket compaired to the cost of a new head is nickle/dime vs. big bucks.

I just did this to my head. It soaked in the tank for 3 days and flushed out. I put evapo-rust in it for 2 days and took a power washer to it and the inside looked like a new casting. Another 2 cups of scale came out. It can be bought at Advance Auto and the same thing WD40 brand can be bought at Walmart. It is completely biodegradable and can be reused. I plugged the holes on the top and leveled it. 1 gal is enough.

I just reviewed the Evaporust videos on YouTube. Very interesting. Great to know. Thanks, I am always learning something on this forum.

In these years (33 to 36) they placed water "jets" in the heads. These jets shoot water onto "hot spots" in the head. These jets are easy to plug up as the hole is about pencil size. When they plug the head runs hot. It is real important to keep these free and totaly open.