Jumping Gear

If you have a Model A that jumps time, check the distributor/oil pump gear.  The later models gears were pressed on the shaft and could slip.

This tech tip was provided by John Walliser and was printed in the Jan./Feb. 1987 “A” Quail Call.

Model A Fan Airflow

There has been a lot of discussion about which is the best fan to keep that Model-A temperature the coolest. Is the original 2-blade metal fan, the later 4-blade metal fan, or the aftermarket 6-blade plastic fan the best?

For this test a sophisticated instrument was used to measure the air speed in MPH (Miles Per Hour) at three different engine RPM’s (Revolutions Per Minute).  The results are not scientific but do give a good indication of which fan produces the most airflow.  The tests were performed on a stationary vehicle.  The following tests indicated the fan air flow MPH speeds with engine speeds of 500 RPM, 1,000 RPM, and 1,500 RPM.  The measurements were taken at the front right corner of the engine block.

Engine @ 500 RPM Engine     @ 1,000 RPM  Engine         @ 1,500 RPM
       (12 mph ground speed) (25 mph ground speed) (37 mph ground speed)
 Fan         Air Flow                           Air Flow                            Air Flow
 2-blade    7 mph                            18 mph                             25 mph
 4-blade   11 mph                           24 mph                             32 mph
 6-blade    8 mph                            22 mph                             34 mph

 The above Air Flow test results indicate:
1) The 2-bladed fan produces less air flow than either the 4-bladed or 6-bladed fan.
2) The 4-bladed fan produces the most air flow up to 1,000 rpm.            
3) The 6-bladed fan produces the most air flow at 1,500 rpm and higher.
            Summary:  The 2-blade fan should be adequate if the cooling system is up to par.  If not, more fan blades might be needed.  A cars higher speed will increase airflow through the radiator, but also increase engine heat.  Remember, a good clean radiator, correct coolant, and a tight fan belt are essential to good Model-A cooling.

This article was authored by Marvin Melage with data provided by the Model A Times Magazine.

Is A Thermostat Needed?

That is a question that has been kicked around the garage for some time now.  The early thoughts were that a thermostat was needed to slow the water flow in the radiator.  Extensive tests have shown that changes in the rate of water flow through the radiator results in negligible change in water temperature.  A Model A radiator should cool the engine under normal driving conditions.

A good clean radiator, even a stock one, should keep the engine operating at a normal level (160-170 degrees). If your engine is running hot you should look at all of the things that could be cause.  An older radiator, one that appears in good shape and flows well, may have deteriorating connections of the fins to the tubes, which reduces its ability to transfer heat to the surrounding air and is usually the cause of engines running hot.

The original design of the Model A radiator is for a Thermo-Syphon system used in conjunction with a water pump.  The entire cooling system was engineered to use the best of both types of systems.  The thermo-syphon system keeps the coolant in place until the engine reaches an operating temperature of around 180 degrees.  The pump increases the flow of coolant when the engine is operating at higher speeds and the thermo-syphon system would not move the coolant fast enough to cool the engine.  So the Model A was equipped to have a thermostat of sorts with the thermo-syphon system helping the engine warm up before the coolant started moving.  This still doesn’t answer the question regarding installing a new thermostat.  The modern fuel of today requires the engine to operate at above 160 degrees to burn clean and with the most efficiency.

Tests were made using a new reproduction radiator along with a high compression head.  The Motometer temperature gauge (thermometer) on the radiator cap takes it’s readings through a special stud, mounted in the motometer.  Through many operating conditions, the thermometer never rose to the operating range on the motometer.  A modern temperature gauge with degree readings was then installed along with a temperature sensor mounted in the upper water outlet neck.  After running the Model A through many operating conditions it was surprising to find that the newly installed temperature gauge never rose above 140 degrees on a hot summer outing.  After seeing the engine operating so cold, a 160-degree thermostat was installed in the upper radiator hose.  In a short period of time the engine water temperature now rises to 160degrees F as seen on the water temperature gauge.  The opening and closing of the thermostat can be seen on the temperature.  The gauge displays change as the indicated temperature rises to 170° and then drops to 160° as the thermostat opens and closes.

Installing a thermostat will allow the engine to operate at the most efficient temperature range, getting the most out of the fuel that is being used and at the prices we are being forced to pay you best get the most out of your money.  This is an easy and beneficial improvement that will make your Model A operate at an efficient temperature level, allowing complete and proper burning of the fuel, thereby reducing unburned fuel and fuel contaminates that produce carbon buildup and sludge in the engine.  The illustrated thermostat can be purchased from any Model A Parts Supplier in temperature ranges of 160° or 180°F operation.  Installing a water temperature sensor in the upper water outlet neck and a water temperature gauge, will provide a more accurate indication of your engines operating temperature.

Cleaning Dirty Spark Plugs

When the spark plugs are dirty, they demand a really good cleaning.  You can take care of the job yourself by buying a bottle of household ammonia.  Simply soak the plugs and they will emerge cleaner than sand blasted ones.  The ammonia loosens the deposits and floats them away.

Diagnosing a Cylinder Miss

On our way to the Spring Banquet this year, my wife and I were riding with Les Meacham in his Fordor Sedan, following Don Harvey in his modified Tudor Sedan.  Suddenly, two puffs of smoke came out of Don’s exhaust pipe.  He immediately pulled off of the road into a vacant parking lot and we were right behind him wondering what happened.  Without opening the hood, Don said, “The head gasket blew.”  I don’t know how he knew this so fast, past experience I suppose.

He opened the hood and took out a long screwdriver from his bottomless toolbox and showed Les and I how to check which cylinder or cylinders are affected.  He held the screwdriver blade to the head, with the engine running, and had the shank of the screwdriver to the spark plug wire.  If a miss is noticed, that cylinder is okay.  In checking the others, if no miss is noted, that’s where the gasket is blown.

Flying into action, Don pulled out the appropriate tools to remove the head as cylinders three and four were affected.  Now taking the head off of Don’s engine is no easy matter, as there are water hoses for his hot water heater, wires and assorted plumbing for horns and whistles.  He removed the head, replaced a new gasket and had the car running in just forty minutes.  Being a novice in the mysteries of Model A’s, I was impressed with his instant diagnosis of the engine and fast repair.

The whole point of this story is knowledge and having spare parts and tools, including a torque wrench for the head bolts.

This tech tip was provided by Tom Easley and printed in the June 2004 “A” Quail Call.

Ruling Out A Blown Engine Gasket

When all the symptoms point towards a blown head gasket, like loss of power and backfiring, try this quick and easy way to confirm the diagnosis.  First, you will need to take out all the spark plugs.  Next, take a section of paper towel, roll it up and push it into the removed spark plug hole.  When you have all the spark plug holes plugged with paper towel, roll the engine over and see if the entire paper towel is blown out of the spark plug holes.  The paper towel that remains in the hole will indicate a loss of compression in that cylinder.  The loss of compression will keep the gas from firing and force the raw gas into the exhaust pipe.  That will cause backfiring and a loss of power.

If a blown head gasket is indicated, it is time to take the engine head off and replace the head gasket.  Once that is completed and the head is back on and tightened to 55 foot-pounds, it is time to recheck the timing of your car.  A nice tool to use to get the first cylinder piston to top dead center for timing the car is one available from Eastwood.  It is called the “Whistler” and is part #46048.  Once you have this tool, you will need to make an adapter so that 18 mm will fit into the Model A spark plug hole.  The way it works is as the piston rises, compressed air escapes through the whistle.  When the whistling stops, the piston is at top dead center.  Then you can set your distributor to the first pole and the car should be timed.  Good luck and I hope this little technique helps you solve your engine problems.

This tech tip was provided by Jeff Johnson and printed in the September 2003 “A” Quail Call.