Aug 13, 2011
Explosions in the muffler can be the result of intermittent ignition, throttle open and after-burning in the muffler due to lean gasoline mixture. Muffler explosions can occur if the ignition is turned on after the engine is cranked. The cure is to turn on the ignition first. If slight muffler explosions are heard when running downhill with the car in gear, ignition on and the throttle closed, see that the gas mixture is not too lean and that the spark is advanced all the way. Some causes of backfire are cold engine, spark retarded, mixture too lean, dirt in the carburetor, leaking through the intake valve, excessive clearance on the exhaust valves. The lack of sufficient fuel can create overheating of the exhaust manifold, which in turn creates popping noises. Clean out the fuel lines and adjust the carburetor for a possible cure. Symptoms of a leaky manifold are rough idling and poor performance. You can place a few drops of oil around the leaky gasket under the manifold. If the oil is sucked into the manifold and the engine changes in its idle, you could have an air leak at that point. If so, replace the gasket, but make sure the mounting surface is not too badly warped. The clamps holding the muffler to the exhaust muffler can let go with a bang! Don’t forget to check the muffler clamps often for looseness. When you tighten the nuts holding the exhaust and intake manifold in place, be sure to pull the nuts evenly, tightening each a little at a time. This procedure will prevent leaks and prevent the manifold from cracking which sometimes happens. Lastly, the smoke coming out of your tailpipe is telltale. Too much fuel or too little air creates black smoke to trail from the tailpipe. Excessive oil burning causes blue smoke. White smoke is caused by moisture and can be caused by head gasket problems.
This tech tip was originally printed in the Mar/Apr. 2000 “A” Quail Call.
Jun 4, 2011
After a period of use your Zenith Carburetor may develop seepage. The cause is usually the compressed paper gaskets under the jets in the bowl and under the metering valve, which the float operates. If this occurs, remove the carburetor and separate the halves. A 5/16” nut drive will fit the cap jet. Remove the bottom plug. Using a common screwdriver, tighten the main jet (next to the cap jet). Then tighten the compensator jet in the bowl. Next remove the float pin and float. Take a 5/8” 6-point socket and tighten the metering valve, 10 foot pounds, using a ½” drive torque wrench, or 150 inch pounds with a 3/8” drive torque wrench. Re-assemble and use. If seepage should recur, there may be a small foreign particle holding the needle off its seat in the metering valve. Remove the metering valve and blow out with air. If seepage returns, recheck all jets for tightness. Then check fuel tank, filter and lines for dirt or foreign particles.
This article was printed in the May 2008 issue of the “A” Quail Call.
May 21, 2011
The rotor position shown below is the proper position with the timing pi in the gear depression and piston #1 at the top of the cylinder. The dashed line shows the position of the rotor when #1 fires with the spark lever fully advanced (down). NOTE: This is for reference only and not a suitable method for final adjustment of the timing.
This article was printed in the May 2009 issue of the “A” Quail Call.
May 7, 2011
Anyone that has tried driving a model A with a V8 pressure plate just won’t go back to the standard “A” plate. It takes about half the pressure or less to depress the pedal. “What a difference!” It also eliminates clutch chatter. For a touring car this is a must in the author’s opinion.
But as far as I’m concerned this is not enough. When cutting down the rim and face of the flywheel, you should take it one step further and lighten it. I mean don’t mess around, cut it. I lighten a flywheel to 37 lbs. starting off with 64 lbs. This is quite a reduction.
I once had a flywheel in my garage that I thought was too light to use in a sedan. I gave it away to a friend who was building a Speedster. I felt that you needed some momentum that is created by the flywheel. Well, after some experience, I now know we are not driving tractors.
The benefits of a lightened flywheel are many. A lot less stress on the rear main is one of them. Quicker acceleration and deceleration is the most beneficial to most of us with standard transmissions. It makes shifting a lot easier and with patience can even shift without double clutching. Even going to a lower gear is easier. Not one person that has “lightened up” has regretted their decision.
This article was printed in the June 2010 issue of the “A” Quail Call by AJ Pennington.
Apr 2, 2011
The Model A had a thermo-siphon cooling system. Coolant is not only pumped through the system, but is also circulated by hot water from the engine block forcing the collar water down through the radiator and back into the water jacket in the block. All cooling system components must be in good condition to ensure efficient cooling, but in this article we’ll focus on the radiator.
The Model A radiator consists of a top tank and a bottom tank joined by a series of either round or oval metal tubes, depending on the vehicle and year of manufacture. In operation, the engine-driven water pump supplies water to the top tank which flows through the tubes to the bottom tank and then back to the engine block. Thin sheet metal fins secured to the tubes serve to dissipate the heat of the water flowing through the radiator. The system is open to the atmosphere and is not pressurized.
An overflow pipe is soldered to the radiator frame in two places and extends to the bottom of the radiator. On the ’30-’31 models, there is a hole located in the frame cross-member so that overflow water can fall straight through to the ground. The ’28-’29 models did not have this hole. Some “driving” car builders have added a rubber hose extension to the pipe so that overflow water does not drip on the front spring or axle.
The amount of water that can be pumped through the cooling system is determined by how much water the pump can deliver and how much water can actually flow through the radiator itself. Pump output is dependent on engine speed and under Model A era driving conditions the pump normally did not deliver more water than the radiator could pass. Times change and today’s Model A can be driven at speeds much faster than were envisioned at that time. As a result, it’s possible to pump more water at highway speeds than the radiator can handle. If this happens, the excess water will either flow out the overflow pipe or from under the radiator cap. When you lose enough water, the engine will overheat.
The original Model A radiator could pass from 38 to 43 gallons per minute (flow rate) depending on tube configuration (the ’30-’31 4 row AA Commercial radiator could pass 48 gallons per minute). However, over time, several factors conspire to lower the flow rate:
- Corrosion and mineral deposits inside the tubes.
- Pinched or dented tubes caused by stones or other external factors.
- Damaged tubes removed from service by well meaning, but ignorant, radiator service shops.
Another important, and often overlooked, factor is the replacement of a worn-out or damaged radiator with a reproduction type. In many cases, the “repro” actually has fewer or smaller diameter tubes than the original. It’s no wonder that the flow rate of some “repros” may be less than 30 gallons per minute. A conversation with one reproduction radiator manufacturer revealed that he did not even know the flow rate of his product! For this reason, the Model A owner may be better off restoring the original radiator than installing a reproduction.
A good radiator shop will perform the following steps when rebuilding or repairing an original Model A radiator.
- Measure the flow rate before doing anything else. This can be rechecked later to verify the effectiveness of the repairs.
- Use a caustic solution and ultrasonic equipment to thoroughly clean the tanks and tubes.
- Replace and repair any damaged tubes, maintaining the original number if possible. Extensive radiator damage may require that some tubes be pinched off and soldered closed.
- Reattach loose cooling fins to the tubes. A fin not secured to the tube will not dissipate the heat. In the original radiators, fins were individually soldered to the tubes.
- Lightly paint the radiator with special radiator paint to prevent corrosion. It should be noted that any type of radiator paint or primer will impede heat transfer to the surrounding air but is a necessary evil to protect the radiator.
- Check the flow rate of the refurbished radiator. Remember, a good radiator should be able to pass from 38-43 gallons of water per minute (48 gallons for the ’30-’31 4 row AA Commercial radiator). Any less could be asking for trouble.
Few radiator shops have the equipment or expertise to measure the flow rate and some will maintain that this is not even necessary. Actual experience has proved otherwise and it’s worth the effort to find a shop equipped to do this measurement.
Sometimes a simple back flushing of the engine will clear up an overheating problem. This can be done after the radiator have been thoroughly cleaned. One precaution should be observed if this procedure is used. DO NOT use more than five to seven pounds of pressure or the radiator may be damaged. Original cooling system components were not designed to operate under pressure.
Some controversial consideration…
The following items are considered controversial by some Model A enthusiasts but in my opinion offer some very real and practical advantages:
- Antifreeze coolant – Use of a good antifreeze provides freezing protection if you want to drive your “A” during the winter months. In addition, the built-in rust inhibitor will help keep your cooling system rust and corrosion free. Modern coolants also include a special water pump lubricant, which can extend the life of your pump. In contrast, plain water can promote rust and scale and offers no freeze protection or water pump lubrication.
- Thermostats – Any gasoline engine runs better at a constant temperature because the gasoline vaporizes more evenly. In addition, engines operating at a temperature of at least 165 degrees will evaporate combustion chamber water resulting from the combustion process, helping to prevent rust. A third benefit provided by the thermostat is to act as a “restrictor” at high speeds and reduce the flow rate through the system. This can help prevent water or coolant overflow under highway driving conditions.
Incidentally, if a thermostat is installed, a 1/8 diameter hole should be drilled through the valve plate to allow a small amount of water to circulate through the cooling system at all times. This will ensure that heated water from the block will actually reach the thermostat and cause it to open. If this is not done, the engine may be running hot and the thermostat will not sense the overheating.
More controversy…
If you plan to do a lot of driving at highway speeds, you might consider grinding a little off of the water pump impellor ears to reduce the water flow. This will also reduce flow at lower speeds so it should be done a little at a time. Grind the ears evenly to maintain impellor balance. It would probably be a good idea to check out this procedure with friends or fellow club members before you start!
(Note: Additional information on water overflow and radiator baffles can be found in the April, 1930 Ford Service Bulletins).
This tech tip was originally provided by Walt Wawzyniak and printed in the June 2001 and the August 1992 “A” Quail Call.
Feb 6, 2011
The next time you do engine work, throw away the pistons and install new ones with cam ground .020 or less! Until recently, most replacement pistons were cam ground as much as .040, too much for the “A” that never reaches the 220 degrees of your late model car. This will result in poor compression and blow by.
Normal choking and blow by will dilute the oil rapidly at about the same rate you burn oil; 500 miles per quart. The level on the dipstick remains high and becomes the consistency of cutting oil in 1500 miles. The “A” normally runs too cool to boil off the gasoline.
On new pistons the thrust surfaces are usually about .003 under bore size. They must be trying to tell us something here, but just try to obtain factory spec clearances. The engineers are always out to lunch. I shoot for .002 side clearance, so far so good.
You will be pleased with the increased performance and will, after the break in, have at least 20# more compression than your buddy’s ride.
This tech tip was supplied by Pete Amsler and printed in the June 1997 “A” Quail Call.
