Can a rich mixture make a flathead boil over?

S

storyteller

Member
I installed a brand new Stromberg 97 on my 1939 flathead. It started right up and I noticed a very rich exhaust. It ran fine for maybe 10-15 minutes. This car NEVER overheated in years. Could it be that the very rich mixture would cause it to boil over? I was just about to adjust the idle mixture screws when she puked all over the place. Glad my hands weren't down in there!
 
storyteller said:
I installed a brand new Stromberg 97 on my 1939 flathead. It started right up and I noticed a very rich exhaust. It ran fine for maybe 10-15 minutes. This car NEVER overheated in years. Could it be that the very rich mixture would cause it to boil over? I was just about to adjust the idle mixture screws when she puked all over the place. Glad my hands weren't down in there!
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Mine runs warmer with a lean mixture.

Vergil
 
In general, a rich mixture has a cooler combustion chamber than a lean mixture. Normally to lower exhaust gas temperatures you richen the mixture and vice-versa to raise it.
 
When it first started there was a lot of white smoke coming out of the tailpipe. It filled the garage with a very stinky-gassey smell. The car is on dollys so I pushed it around so the tailpipe was pointing out the garage door. I had to turn on the exhaust fans. Another thing I noted, the temperature gage therometer never did go up even though it was boiling out hot water/antifreeze around the radiator cap. It stunk so bad, I assumed that it was too rich. Some other guys say lean is hotter and rich is cooler. I ran it last summer for over an hour and it never got overheated. This was the first time I started it this year. (the only change was the carb.)
 
is it a stromberg carb or one from Speedway??.....white smoke usually means coolant leak....was coolant topped off before starting??...do you have thermostats??....Mike
 
Do a pressure cheak on you radiator and see what happens, probably coolant if there was that much smoke. Put your hand in front of the tailpipe and see if there is a smell of burnt anti-freeze, white smoke is usually coolant, blacker smoke is usually tells you its to rich.
 
Based on all the posted info, I'd be tempted to think you developed a coolant leak over the winter or when you started it up. Check compression and, if possible, check coolant for the presence of combustion by-products. Good luck.
 
Rich combustion produces black smoke. Coolant produces white smoke. A combustion leak into the cooling system will pressurize the system and puke out the coolant without necessarily showing hot on the temperature gage. It does sound like a leak between the cooling system and combustion chamber/s.
Further checking should show the problem.
 
I agree. The white smoke is coolant getting into combustion chambers somehow. Rich mixture burns cooler, lean burns hotter. To understand this, think about your acetylene torch. Lots of acetylene with little oxygen burns cool--just makes a lot of soot but not enough heat to cut or weld anything. That's what a rich mixture is, way more fuel than oxygen. You get soot or black smoke, which indicates incomplete combustion because there's not enough oxygen in the mix to support full combustion of the fuel. Decrease the acetylene and increase the oxygen and the flame gets hotter. That's what a lean mixture is, way more oxygen than fuel, which burns very hot.
 
If your car was stored over the winter with coolant in the system, there is a good chance that the head gasket has developed a leak. Your symptoms of white smoke and a sweet smell indicate a coolant leak of anti freeze in a cylinder. The added indicator that the water temperature boilded over was not necessarily boiling over but the escape of compression gases into the cooling system giving the impression that the engine was over heating but not true as evidenced by the temp gauge low reading.

You probably have a blown head gasket. Pull the spark plugs and check for condensation on the plug , rust or a super clean plug and that will indicate the offending cylinder. If you have this issue you will have to pull the head replace the gasket and check the cylinder wall for rust pitting damage.
 
Also if some coolant leaked out, there is a good chance that the temperature sensor was not in contact with the coolant. Hence no hot reading on the gauge. If you use thermostats(and you should) be sure you drill a small hole or two in them to allow air to escape when filling the system.
 
A stuck thermostat wouldn't make white smoke. White smoke indicates a compression leak. You indicated it was running for a while before it blew the water. You can tell which side of the block has the leak by removeing the two top radiator hoses and install two short srraight hoses a few inches long. Remove the fan belt, fill the water up into the hoses and start the engine. Let is run at a fast idle watching the water in both hoses. If you have a compression leak bubbles will come up in the side that leaks. If the bubbles are less the 3/8" in diameter it is a small leak and barrs heavy duty stop leak will usually stop small leaks. Put the hoses and belt on, make sure your pressure cap seats down on the bottom seat if you have a radiator with the over flow in the neck. If not put a thin plastic tube over the radiator overflow tube and AFTER you get the engine temperature up to 200 with the barrs leak clamp the hose closed and shut it down in two minutes. Let it cool over night with the cap on tight and the over flow closed off. This trapped pressure will force the barrs into any small pin hole leaks sealing them. You don't want to close off the over flow until right before you shut it down so you don't build up to much pressure and blow something. G.M.
 
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