The Stovebolt Site Forums The Shop Area Engine Shop Is white smoke normal for an engine that has sat?

I am getting a lot of help so far on these boards so thank you in advance.

Long story short, recently acquired a 1953 Chevy 3100 that has a 1955 235 swapped. I did all of the recommended things on the tech page to get an older engine going again. It probably sat for 20 years. What is the main cause of white smoke coming from exhaust, mainly on acceleration? During idle it seems clear. The truck also seems to be running extremely rich, and I can smell heavy exhaust fumes. Is this normal for an engine that has sat for that many years? Is it burning off condensed water somewhere?

My initial thoughts are head gasket or it needs to be ran a few times up to temp to get all the moisture out.

White smoke usually means water in a gasoline engine. What does the oil look like? Have you cracked the drain plug after it sits for a while. Water will come out first. If you have no signs of water, possibly someone poured in a bunch of something like Marvel Mystery Oil to preserve it. Things like Marvel Mystery Oil will blow white smoke for a long time. But it prevents rust and dissolves carbon.

Oil looks good. I haven’t cracked the drain plug but probably should.

Hoping I’m not losing coolant/water. I’ve been checking the radiator frequently and so far it seems good.

New should have been a first step on the list?

Run it, drive it to see where it is coming from. Put a few tanks of gas though it looking for the issue. No major damage is going to happen.

1. After a good run let it sit and check oil. Any milk? If so probably a head gasket or cracked head and the vapor is burning off through the oil.

2. Could still be a head gasket from a water passage, but you will have to pull plugs to see. One will be super clean.

3. If everything checks out maybe not getting up to temp and the exhaust temps are not able to suspend the moisture all the way out of the pipe?

Thanks for the suggestions, I will do that.

The tech tips called for changing the oil after your first initial start (once you’ve warmed the engine up so the oil is hot). Of course it also called for checking and topping off the oil as needed. Oil looked normal to me, I just needed to add about a half a quart.

The white smoke isn’t overwhelming, but enough that it made it uncomfortable in my shop even with the door open. Definitely running rich or burning off some old crud. I checked the radiator this morning, it seemed normal. Also checked the oil again and it seemed normal.

I am leaning towards fuel quality issues. I put a new hose on the fuel pump to a gas can, blew out the line between the pump and carb, added a new filter, and rebuilt the carb. Is it possible there is still old gunky fuel in the pump itself that needs to work itself out? I might as well get a new pump so I can eliminate that.

Another question I had is that the truck does not want to start after you stop it. It will just crank and crank. I think that's because I am running the line into a gas can rather than gravity feeding from the tank down to the pump.

If you have a Rochester carburetor (and the likelihood is very high that you do), the super-rich running will be from a stuck power piston. There are lots of articles about that here (many I've written). When the piston fails it sticks in the "down" position and this leaves the power valve open (a simple spring-loaded ball) allowing a lot more fuel to enter the manifold. Time will never fix this...you have to disassemble and clean very well.

If you're fortunate enough to have a Carter carburetor, the super-rich condition will be from a failed diaphragm (accelerator pump diaphragm some will call it). If it has failed, vacuum will suck gas straight out of the float bowl and in to the manifold. I've written about that too, but we're not currently adding to tech tips so it won't be there.

Please let me know if you want me to resurrect any of the old carburetor articles for you.

Hi Jon, thanks for the reply.

Yes I have a Rochester. I fully rebuilt the carb. I read quite a few articles including one on the stuck power piston. It was indeed stuck in there. I didn't need to use heat, I was able to squirt some penetrating oil in there and it came free with a little force. It moves up and down freely now from what I can tell. The power piston is vacuum controlled correct? If I have a vacuum leak, which I am certainly leaning towards, would this cause rich running symptoms? I believe I have a vacuum leak somewhere between the manifold and wiper motor. It looks a little suspect to me.

These old trucks have no cat on them. It will not take long to drive you out of a garage. My 4 stroke smowmobile has no cat and it will drive me out of my 3 car garage with 5 min of idling.

Excellent point haha. I still have no brakes on the truck, need to address that next. But I suppose it wouldn't hurt to pull it out of the garage if I am going to be running it. Just need to get the new gas tank in first also!

Now that you have it running, it needs a good hot run out on the street. Idling will not do it. Get a load on that motor and drive it. Lets see what its doing under actual operation. A good long run is likely to burn off any junk, crud or accumulated sh&t in the motor. Now you can go through the normal diagnostics, compression, tail pipe emissions, carb adjustments, timing adjustments, check coolent, check oil.

Excellent advice, thanks.

I will get the new gas tank in, address the brakes and give her a good long run on the street.

Rochester carbs have a bad habit of warping the top cover, which creates an internal vacuum leak that keeps the power valve open most of the time, creating an over rich mixture. There is a procedure to straighten the cover which works at least temporarily. Make that carb a stinky paperweight and find a Carter carb to be a long term solution. White smoke is usually condensation in the exhaust system, which will be resolved by a highway run under load. If the engine has been idle for a long period of time, the rings might be stuck in the grooves in the pistons, resulting in low compression and oil consumption. I add 2-3 quarts of Diesel fuel to a full crankcase of cheap oil, and run the engine at a fast idle for 20-30 minutes. DO NOT drive the vehicle or put the engine under any kind of load with the thinned out oil on board. The crankshaft and rods splashing into the overfilled sump will splash the inside of the engine like the agitator in a washing machine, dissolve sludge and debris, and free up the rings. Drain the hot oil and refill with 15W-40, and change the oil filter.
Jerry

Is there a method to testing the top cover of the carb to see if it's warped? I assume a nice metal ruler would tell you if you're off square or not?

While you have it running, spray some carb/choke cleaner all around the carburetor base and the seam where the top joins the body. If the engine revs change you have found your vacuum leak and likely point of warpage.

When the carb is off the car and taken apart, lay the mating surfaces of the parts on a piece of window glass and look for gaps. A metal straight edge works, too, of course but the glass method is a little easier

I will do that. This truck also has about a 1" throttle body spacer between the manifold and the carb. I noticed there wasn't a gasket between the spacer and manifold, so I added one. I also have one between the spacer and the carb. Is this the correct method?

Carter's sales slogan in the 1950's was "The ABC's of fuel systems- - - -Always Buy Carter!" There's a very interesting story about Carter producing direct-replacement carbs for Rochesters, and the CEO of Carter vowing to sell a million of them. It took a few years, but when the one-millionth carb came off the production line, it was gold plated and presented to the CEO of GM. Patching up a Rochester will keep a stovebolter too busy to engage in very many vices in his spare time, though!

If the spacer (actually a heat insulator) is flat, it doesn't need a gasket on the manifold side. Scuff it on a piece of sandpaper supported by a sheet of glass to check for flatness. Be sure the carb to spacer gasket has slots in the proper location to prevent blocking off the vacuum passages.
Jerry

A gasket isn't supposed to be required between the spacer and manifold.

I use one because I had a vac leak there even though a straight edge showed the manifold was straight.

A gasket is required between the spacer and the carburetor.

I'm wondering if the white smoke you're experiencing is from MMO or Seafoam or some other oil the previous owner put in the cylinders to keep them from rusting up while the truck sat around.

That is very possible.

Based on all the information I have gathered I think I will start by ensuring no vacuum leaks. I am fairly confident the carb is functioning correctly other than possibly being warped - again this might be a vacuum issue. Whenever I blip the throttle it sure sounds like air coming from the engine bay. If I give it a slow rev it seems to do ok, and this is when the white smoke seems to pick up.

If I can figure out why it won't start on it's own this might resolve both issues. Whenever I shut the truck off it will not start again without a little drop of gas in the carb. I am hoping the new fuel pump and tank will solve this issue. I would really like to get the truck running and take it for a drive to see if the smoke clears up. But I would hate to go too far without knowing my fuel pump and carb are functioning correctly.

Any recommendations on a fuel pump for my 235? It was built in 1955.

Find an original pump and have it rebuilt or do it yourself.

The pumps on the market today are all made in China. They are junk straight out of the box. You can see my recent experience with two such pumps in another thread a few lines down from this one.

I had the original pump rebuilt by Then & Now Automotive and works as it should.