VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 To idle in traffic - fast or slow?

Just got back home in my 39 Mstr Dlx from the post office mailing my accessory steering wheel to get recasted. Looking for some coventional wisdom. No one goes anywhere quickly on a Friday afternoon in the Washington DC area. So, when I'm backed up in traffic or sitting at a long red light, is it better to idle at the normal speed setting or is it better to pull out the throttle knob a bit to idle a lttle higher - turning the fan and water pump faster?

Or, am I just thinking too much while sitting there watching the temperature gauge rising towards the red marks?! Just wondering.

The most important thing is to shift into neutral.

When you have your foot on the clutch you are providing an additional load for the engine.

This pressure on the clutch is transferred to the flywheel and as a result pushes the crankshaft to the front. This will cause additional wear to the thrust bearing.

If you follow this rule you may not have a serious overheating problem.

Thanks Ray. I always do that because I had my foot slip off the clutch once in another car - that was exciting! I'm using an original heater shut-off valve and don't know if that would make the engine run a bit hotter or if there's any back pressure from the water pump into the heater unit. I'd think there shouldn't be any additional pressure because the shut-off valve is on the heater supply line (top of water pump) if I remember right. I raise that because my heater started leaking only AFTER I installed the valve - never when the water was flowing freely.

Fast is best.It not only circulates the water better but the oil also. The fan turning faster draws more air thru the radiator. Went I drove my '39 in prades I always pulled the throttle out so the engine was at a good fast idle, about 1200 RPM. It would run hot but never boiled on a 90 Deg. day. It not unusual for the needle to hit the 200 Deg. mark. If your running a 50/50 antifreeze mixture it will not boil till over 220 deg.
The only time I had my '39 throw out coolant is when we were in Colorado in 1976. If you were making a steady climb and would stop (I always run the engine fast for about 2 minutes before shutting it off) it would puke out a little coolant. The needle wasn't that high but water /coolant boils at a lower temp. at high elevations. I eventually installed an overflow tank and on its second trip to Colorado everything was fine. A pressure cap would help also but you can't used one on a 1939 or older.
In general the 1937-40's are not cool running cars. On a hot day mine will run over 180 on the highway...a little more or less depending on the wind direction. I installed a new radiator when I first went thru the mechanicals and a new block six years later so everything is as new. When several of us used to travel together with our 1937-40's we all ran about the same but never really cooked.

Hi Gene, It's been a long time. Thanks for the info - you confirmed what I was thinking made sense. Mine puked about a half a cup the other hot day after shutting it down. I had parked and immediately turned off the engine. I now have an original overflow tank I'll install soon to take care of that sort of thing. By the way, did you see my comments about my heater developing a leak. It was always fine before I installed the heater shut off valve and then a while later it developed a leak. Seems bizarre - like it sound have leaked when water was flowing through all the time instead of after the valve was closed. Any thoughts? The shut off valve show makes a more comfortable ride in the summer.

My heater has an original 1939 shut off valve and I always leave it open....acts like a little extra radiator. Never told my wife it could be shut off. Used to run the heater in prades to help cool. Strange about the leak. My '50 developed a leak. I installed a shut off valve for both hoses for the trip to Colorado....and its still that way. Forgot all about it till now.Never need the heater in Summer.
With out an overflow tank its best to keep the water level down a llittle lower. Just so you can see it when cold. The '39 is not easy to see. The first year we were in Colorado I thought I could see the water so never added anything, On the trip ome the engine was running hot. I finally pulled over and removed the thermostat. (lot of good that does)...I unbolted the thermostat housing with out draining any water and nothing came out. It was that low. Probably what eventually help crack the black and head. It ran hot but didn't boil - the water probaly never got up to the sending unit to tell the correct temp.....live and learn by experiance-the story of my life.

I lowered the level in my 38 HB and my car quit "puking". TX heat can be brutal. Mac

I have found that if the water is just at the very bottom of the tank when cold and about mid way when hot it will not puke except in extreem conditions.

Ralph,
I've pondered the idling oil question for a decade or two. At idle your oil distributor valve is closed, keeping oil out of the connecting rod nozzles. This isn't terrible, since you don't have much bearing load at idle. HOWEVER, you need some oil pressure to open the oil distributor valve to refill the dipper troughs. I have concluded that the troughs will eventually run dry after extended idling. I have never seen a warning about this in any Chevrolet literature.
As engine speed increases from idle the oil gauge will show pressure correspondingly increasing, then level off for a while. That is the point where the distributor valve opens, refilling the troughs as well as activating the pressure stream oiling system.

It wasn't until 1952 or so when the head was drilled for coolant bypass when the thermostat was closed. On these earlier 216 engines its best to let some coolant circulate thru the heater to prevent steam pockets toward the rear cylinders before the thermostat opens. Also on cooling, the thermostat restriction, especially at higher flow rates--at high speed--creates positive coolant pressure in the block which also helps prevent boiling. That's why you can boil over if running without a thermostat.

In the 1970s I started opening my hood after shutting down to lower peak "hot soak" temp. Gas had a higher vapor pressure then and boiled out of a carb easily. That trick kept the float bowl full, and should help prevent coolant spit on the hottest days.

I respect Bob's knowledge and advice but I must beg to disagree with one statement. The oil to the rod troughs continues at idle just as the rocker arms recieve oil at idle speed. The cars from 1935 and up have the pressure stream system for lubricating the rod bearings.At low engine speed and low oil pressure the troughs are fed enough oil to keep them full. As the speed and pressure increase the stream rises and shoots directly into the dippers.
To quote the 1935 Engineering Manual "At low speeds and when idling, sufficent oil for good lubrication is fed into the oil troughs which act as oil reservoirs from which the connecting rod dippers dip oil as they revolve."
Prior to 1939 the rocker arms recieved their oil from the low pressure side of the pump. In 1939 the oil distributor valve was changed and they recieved oi from the high pressure side, just as the connectimg rods did.
I do not recommend the engine idle for long periods of time as little oil is thrown up to the cylinder walls and wrist pins.

Gene & Bob,

Thanks for all the good scoop. I really appreciate the insights and experiences. I learned to keep the level a bit lower after I had a really bad puking experience when I had filled the radiator too high. I also started opening the hoods after a drive to help things cool a bit faster, to include the carb to reduce the boil out. Hope to install my overflow tank this week. Take care, Ralph.