the Model 'A'


3609 Traci Lane
Byrnes Mill, MO 63051-1047
Phone: 636-677-7201

Notes to audience:
My name is Terry Oberer and have been driving Model "A's" since I was old enough to get a driver's license. I have been a MARC Member since 1958 at which time we created the Missouri Valley Region and got our charter in 1959. I was so young that my mother or father had to drive me to the meetings at members homes.

This will be an informal seminar so if you have a question or comment during the talk please raise your hand so we may all benefit from your knowledge and experience. The talk will be illustrated with slides and the table up front will display some of the problem parts that we will be talking about. The text of this talk will be available at no cost in printed form at the table up front after the formal seminar is over. Hopefully we will have time then for some individual one-on-one discussions.

In this session we not cover authenticity aspects or fine point judging. We will assume that the vehicle is reasonably authentic. We will assume that the car has been operating normally and has developed some problem or just will not start. Trouble shooting in the garage is easier as time and basic test equipment is available. When an on the road breakdown occurs many tests, while not sophisticated, can be quickly performed which result in pinpointing common faults encountered while driving the Model ''A.'' On the road repairs can be most often handled quickly using a little ingenuity and common sense. Repair suggestions and parts cautions will be made as we proceed. What we want to avoid is a haphazard attack which will do more damage to otherwise functional parts and end up creating a bigger problem that the original fault. What we want to do is look at symptoms and quickly find the defect and correct it and any resulting faults.

Here we will assume that the engine has quit suddenly while driving and will not restart. Remember that an engine needs three basics in order to run - Fuel, Compression and Ignition in proper quantity and sequence. A few simple tests can narrow the problem area very quickly.

Sudden stoppage can be caused by dirt or debris blocking fuel delivery. Quick test for fuel: Crank engine with starter six or seven revolutions fully choked. Stop cranking and release choke. Fuel should dribble out of carburetor throat. If it does, go on to ignition test. If no fuel is seen check for fuel in tank. Don't trust the gauge. Remove the cap and while doing so listen for a sucking in of air which would indicate a plugged vent causing a tank vacuum. Remove filler safety screen and use a dip stick. You should have at least two to three inches for reliable delivery. If ok, remove fuel line at carburetor. A full stream should flow when valve is turned on. If not, turn line up or use a rubber hose over the end and blow back into the line and tank to clear debris. The use of a tank valve screen will help to avoid this problem. Older tank sloshing compounds may be turned to jelly by alcohol laced fuels. This problem can be almost impossible to cure on the road short of rigging up a separate fuel tank. Best solution is don't let it happen in the first place. Use only non-alcohol blended gasolines. Carburetor: If fuel supply to carburetor is ok but no fuel dribbled out while choking then remove lower casting center bolt and carefully disconnect choke rod to allow the lower casting to separate from the upper (attached) casting. Do not allow venturi and gasket to fall. Turn on fuel and it should cascade down over the float. If not check for plugged inlet screen or fuel valve by removing these parts one at a time. Blow out float valve. Check screen and also insure that the end of the fuel line does not extend past ferrule more that 1/8 inch or it may be up against the filter screen and flow will be restricted.

Note: Sudden excessive fuel or overly rich mixture can also cause engine to quit. Black exhaust smoke, smell of rich mixture exhaust or overflowing carburetor would be indicators. Check float valve for debris in valve preventing proper seating. Check that float still floats and has not developed brass stress crack or pinhole leak. Solder or shellac shut after draining float. Check float pin for being too short and falling out of pivot. Check float valve body for looseness or split gasket. Check main and cap jets for looseness, splits, or bad gaskets. Check that main thru bolt is snug - carburetor will run rich as main bolt backs out and lower casting starts to drop from upper. Venturi maintains air stream while bowl fuel level rises and fuel spills from throat jets into the air stream.

Hot weather fuel problems are more common now than some years back due to the lowered vapor pressure of current production gasoline. The ''A'' will run fine until a stop is made in hot weather and upon restarting run rough and rich due to the fuel boiling in the carburetor bowl and causing erratic fuel level problems. It will generally lessen as the car is driven (if possible) and the vaporization of fuel cools the carburetor body. Application of water or ice to the carburetor bowl area can be of great benefit. The addition of a thermal break spacer between the manifold and carburetor as on modern cars can also alleviate this problem.

This is the most common area of on the road failures encountered in driving the Model A. We have a basic quick check here and then we'll use a simplified system diagram to isolate the trouble component and then explain various repairs and show some areas to anticipate and prevent problems. Quick test for spark: Disconnect one spark plug brass strip from the distributor terminal and position it with about a 1/4 inch gap to the distributor terminal. Turn on the key and crank the engine. A bright fat bluish-yellow spark should regularly jump the gap. The spark should be as thick as a pencil lead and produce an audible snapping sound. This indicates spark is good but timing might possibly be incorrect due to a insecure cam lock screw. The correct procedure to check timing is as follows: First set point gap to .010 to .022 of an inch with the point fiber block on the high point of the cam. Check all four lobes for uniformity of gap. (Plus or minus .002) It is best to set gap at high side since rubbing block wear will cause gap to decrease. Manually check distributor shaft for excessive side play (.001 to .003 is normal). Less play means a smoother running engine as the shaft won't chatter while rotating and result in variable point gaps. Also check the upper plate for excessive lateral play around the center hole as wear here will contribute also to variable point gap when advancing or retarding the spark. These variances from the ideal are all cumulative and can result in excessive tolerances resulting in poor or no ignition. Once the point gap is set replace the distributor Bakelite body and move the spark arm to the full retard (towards the starter) position. Remove the timing pin and insert it into the timing hole. Remove the rotor and manually slowly crank the engine until the pin just drops into the slight recess in the timing gear. At this position the next instant of engine rotation should just start the points to open and the notch in the cam should be near the number one cylinder contact in the distributor body. (While standing at the manifold side of the engine and looking down on the distributor it is in the approximate four o'clock position.) Remember that the distributor turns in a counter clockwise direction. If timing is not correct, loosen the cam lock screw and turn the cam clockwise to the correct position and re-tighten the lock screw. Turn the engine two full revolutions and recheck that the points just start to open the instant that the timing pin drops into the timing gear recess. Readjust as necessary. Make sure that the cam does in fact lock to the shaft. Some shafts have poor fitting cam collars or the lock screw may need a washer under the head. If rebuilding the distributor, you may want to drill the upper shaft and lock screw for oil access to the upper bushing to reduce wear. The use of the distributor heat baffle can prolong condenser life. Manifold heaters also tend to overheat condensers and some heaters make it impossible to remove the condenser without removing the whole distributor-- not an enjoyable task on the side of an interstate in rush hour in the middle of an August heat wave.

If spark and timing are correct but the engine still does not start, then check for the third engine essential--Compression; to be covered later.


If spark is not present when the engine is cranked with ignition on, then a systematic trouble shooting of the ignition system must be performed. Referring to the basic ignition system diagram we see a series of components and their connections to each other. A fault in one or more locations will create a ''short'' or ''open'' in the circuit resulting in a no spark situation. The ignition system is but a simple series circuit with a voltage source--the battery; a coil to produce a secondary or high tension spark, a means of switching the coil on and off in time with the engine--the distributor; a cam operating the points, and the coil high tension wire connecting to the rotor to distribute the spark to the appropriate spark plug. Also into this circuit a driver controlled keyed switch is placed to ''open'' or ''close'' the circuit at the driver's will. The series of components are as follows: Battery voltage source at the battery #3. To the starter switch terminal #4. From the starter switch to the terminal box stud #5. From there to one side of the ammeter #6. Thru the ammeter to the other ammeter stud #7. From the ammeter back to the other stud of the terminal box #8. Now we begin the actual ignition circuit at the terminal box with our six volt supply going from stud #8 to the coil battery terminal #9. Thru many fine windings of copper wire in the coil to the other terminal, the distributor side of the coil #10. However, before we run to the distributor a driver key controlled switch is placed in the circuit terminating at #11 and switched on and off internally at #12. From the switch the lead runs in a tamperproof armored cable to the base of the distributor for connection at #13. A condenser is attached here to prevent excessive arcing at the points and can be considered to be an ''open'' in the circuit when operating normally. From the base plate connection #13 the short pigtail wire #15 connects the switch to the points where they can then make and break the connection to ground #16 by the action of the cam which is timed to engine rotation. The high voltage is distributed sequentially to the spark plugs by the coil wire and rotor to the distributor body and then to the spark plugs. This is a totally separate system but is combined with the rest of the distributor for simplicity of construction. Quick test: Check both coil terminals for 6 volts #9 and #10 on diagram. Use volt meter (or just a wire touched to a ground) between each terminal and ground with the switch off. The black lead comes from the generator side of the terminal box #8 and should always show six volts. The red lead goes to the ignition switch #11 and should always show six volts when the switch is off and zero volts when the switch is on with the points closed. If no voltage reading is detected at either terminal check to see if the lights work which would indicate satisfactory battery and wiring condition thru the terminal box. If lights do work then remove terminal box cover and see that the black wire from the terminal box stud to coil terminal is tight and in place. You should now have six volts at the battery side of the coil terminal #9. Disconnect the red coil to ignition switch lead and then check for six volts at the ignition switch side of the coil terminal #10. If you now have six volts, then there is a short in the ignition switch circuit. The short could be in the switch assembly and you would be able to get going again by removing the switch cable from the distributor base and hooking a jumper between the coil terminal where the red ignition switch wire was removed #10 and the distributor base condenser screw #13. Or the short may be farther down the circuit in the distributor.

Namely in the lower plate #13 and its associated wire #15 and connection to the point stud. Or the condenser #14 may have shorted out. The most common and easiest to correct is a shorted condenser so the logical step is to remove the condenser and then again check to see if you have six volts at the ignition switch lead coil terminal #10. If the above test showed six volts at both coil terminals with the ignition switch off, remove the distributor cap and crank the engine by hand until the points are closed. Slip a clean piece of paper between the points and turn the ignition switch on. If the ignition switch and condenser is good there should be a six volt reading at both coil terminals and at the point stud #15. If you get a zero volt reading at the ignition switch coil terminal #10, either the switch or the condenser is shorted. Remove the condenser from the distributor. If you now have a six volt reading at both coil terminals, then the condenser is shorted and must be replaced. If removing the condenser did not result in a six volt reading at both coil terminals #9 and #10, then the ignition switch or lower plate and wire to the points is shorted. If the switch is shorted it must be removed from the distributor since it will ground out any jumper if left in place. As a matter of fact a properly working original pop out will ground the distributor when in the off position rendering a ''jumper'' useless unless the switch cable is physically removed from the distributor base. Be sure to remove the paper from between the points before trying to start the car. Quick test for proper ignition operation: Crank engine until points are closed. Turn on ignition switch. Remove coil wire from distributor cap and hold end of wire within 1/8 inch of a head nut and open and close the point arm with your finger. A fat spark should occur each time you open the points. Be sure to turn the ignition switch off when finished as leaving the switch on with the points closed can overheat and burn out the coil and burn the points.

Common ignition trouble areas:
Blown fuse at starter (if equipped), Corroded or broken ignition switch contacts, Shorted (old) wire in the pop out cable, Shorted lower plate bus bar due to loose rivets and cable end spring pressure, Shorted lower plate wire to points due to connection failure or worn insulation, Shorted condenser due to heat and/or moisture. Points physically closing but not making electrical contact due to oxidation (Usually from long storage or moisture or oil on the points), File to get going again. If a fuse blows while driving, the generator system voltage rises and will also cause oxidation or burning of the points. After correcting the cause of the blown fuse and replacing any light bulbs that burned out from the excessive voltage, the points may have to be filed to get the car running again. Point fiber rubbing block may be worn down causing the cam to short to the point fiber block rivet head. Coil may have good spark when cool but go open circuit or short circuit when warm. Coil high tension wire should be of the metal core type, not resistance type as a bad spot will allow good idle but poor high speed performance due to weaker spark at higher RPMs. Distributor's Bakelite body may have cracks allowing moisture to enter and cause mis- firing or cross firing between cylinders one and two or, between three and four.

Reduced or lack of compression will cause an engine to loose power or stop completely. Quick test for compression: Remove all four spark plugs. Place your thumb over a spark plug hole and with the ignition off, crank the engine several revolutions. The compression, if adequate, should forcefully blow your thumb from the spark plug hole. If using a gauge it should register from 45 to 65 psi after three or four compression strokes. Look for uniformity of readings of no more than ten psi difference between the highest and lowest cylinders. Low compression on all cylinders--Check that timing gear has not stripped by removing the distributor cap and crank the engine. If the rotor moves the timing gear is good If the rotor does not move confirm a bad timing gear by removing the timing pin and reverse it in the hole and while cranking the engine ''feel'' if the gear moves. If it does not then the gear is stripped and will have to be replaced to get going again. The use of a good quality laminated fiber (not macerated fiber) gear is recommended. Sometimes the metallic center hub of a gear can break loose from the fiber portion. The gear will run but with a distinct knock similar to a worn tooth knock. An aluminum or brass gear can be used for severe service. Be sure to replace the crank gear also as it also wears but not as visibly as the fiber gears. Check that the crank gear is correctly marked with the alignment mark to the right of the key way. Once in a while one will be incorrectly marked. To reduce timing gear wear an oiler can be fabricated from a standard bolt to replace the side timing gear cover upper bolt and some tubing. The oil supply is from the oil pump plug in the block and is metered by a 3/32 inch hole drilled in the short length of copper tube soldered into the end of the bolt. The hole is drilled so as to spray the oil directly on the gear. It works !

Lack of compression on one or more cylinders--Possible causes are: A ''burned'' exhaust valve. A ''blown'' head gasket (generally between cylinders one and two or three and four, which would show up as low compression readings on both adjacent cylinders). A foreign object lodged under valve head (possibly a carburetor jet) under an intake valve. Can cause loss of power in adjacent cylinder due to fuel being fired in the paired intake port). Illustrated is a jet which would lodge in the valve at speeds over 38 MPH but drop out and allow normal valve action at lower speeds. It was not discovered until the manifold was removed for inspection and re-surfacing. A burned piston due to running with an antifreeze leak into the combustion chamber can erode a significant portion of the piston to cause compression loss. Broken rings and/or scored bore will cause low compression. Illustrated is a piston from an engine with less than 500 miles which was run without water until it seized due to heat. Upon cooling and the addition of water a distinct knock was heard. Cylinder number three was found to be scored and this was the piston from that bore. A minute crack had developed in the piston from the seizure and the opening and closing of the crack during engine operation was causing the knock. Replacing the one bad piston, honing of the bore and replacement of all piston rings restored the engine to use. Excessive blow by from the crankcase breather is an indication of compression leakage past the piston and rings. If compression readings are increased ten to twenty psi upon squirting oil in the cylinders, it would confirm worm rings.

Adequate compression on all cylinders, No distributor movement--Possible causes are: Loose cam locking screw, re- time and re-tighten screw securely. If it won't stay tight check the distributor shaft collar as some collars just slide down the shaft. Cam lock screw may need a washer under the head. If cam is secure to shaft, the distributor drive gear (accessible through the valve chamber) may have a broken drive tang or the press fit of some replacements will allow the gear to spin on the shaft. Replace if required. A broken distributor shaft drive tang due to seized bushings from lack of lubrication or extended storage can also be a problem. Replace distributor shaft as required.

Water pump and fan
Many fractured and thrown fan blades can be avoided. Always before any tour check the fan blade hub area for an indication of a crack. Any blade showing signs of a crack should be TIG welded not brazed. A thrown blade can kill or injure an observer and can do serious harm to the hood and radiator. A common cause of the cracks is turning the engine over by pulling on the fan blade. Don't do it ! Always check the blade for running true after mounting on the water pump shaft and straighten and balance as required. On 1928 - 29's check that the blade does not hit the upper radiator hose or clamp. If you do throw a blade on a tour, if the radiator isn't damaged, you can continue on your way by breaking the other half blade off. That way there is no unbalance and the waterpump is still functional. The ram-air effect will keep the car cool unless you are in slow traffic. Watch the temperature! On long tours a spare blade may be helpful. Many replacement waterpumps are assembled with the front bearing race split in the bottom of the bore. On any pump remove the front bearing and make sure to have the split at the top (no load) position. A lot of kits use a brass sleeved steel rear bushing and a steel nut. The steel nut can rust to the steel bushing during a non-use period and results in not being able to tighten up the packing nut. Sometimes the shaft will seize in the bushing and the bushing will spin in the casting. The use of a solid brass bushing and brass or die cast pack nut eliminates these problems. Some of the packings are not suitable. Use only pure lead and graphite packings. Don't use any with hemp or fiber in their makeup. Some of the new pack nut seal kits work well too. Check the impeller fit on the shaft before pressing it on, some are too tight and will crack the impeller. Despite the instructions in the kits, it is necessary to pin the impeller to the shaft. More than one radiator has been destroyed by having the ''press fit'' let go!

Clutch and linkage
External linkage failure indicated by pedal falling to floor. Shift transmission to neutral while releasing throttle to remove gear load in transmission allowing easy shift lever movement. Coast to safe pull off and inspect external clutch linkage for missing or broken part. Common failure point is a replacement cast iron not forged like original trunnion (the threaded adjusting rod). Sometimes the lever pin can shear or the trunnion nut will pull out of the pedal due to excessive wear from lack of lubrication. (But we would never let our beloved A's to wear that far without some attention.) External release shaft levers have been known to break or wear out. Here replacement is the solution and can easily be done on the car. For an easier-to-use clutch a 1928 multiple disk clutch arm can be fitted with only minor filing of the pedal required for clearance of the trunnion threads. Clutch pedal adjustments are slightly more frequent and exacting but it is worth it, particularly in parades.

Internal Only rarely will the internal release fork break though the shaft pin can shear. Disassembly is usually the only cure. Sometimes the release bearing lubricant dries out and a squall will be heard when depressing the clutch pedal. If greasing the release sleeve fitting does not get lubricant into the bearing, then a temporary fix is to drill a 1/8 inch hole in the bearing outer shell and use a pump oiler to get some 600W transmission oil directly into the bearing. Then plug the hole with a tooth pick. It worked for me!

Non-releasing clutch can be caused by extended damp storage causing the disk to rust to the fly-heel or pressure plate. Generally happens when all parts are new freshly machined, assembled and then stored. Sometimes if not too seriously seized it can be broken loose by putting the car on a concrete surface and vigorously rocking the car fore and aft with the transmission in reverse while someone holds the clutch pedal down. Lately a new clutch problem has appeared with the presence on the market of the Ock brand Japan made spring center disks. These disks appear to be good quality and are exact reproduction of the American made ones except the metal is not tempered. When in use the springs seem to work out on the flywheel side and then jam between other springs and the flywheel mounting bolts. This jams the clutch disk and it will not release by depressing the pedal. The only fix here is disassembly and replacement.

Most transmission problems can be traced to worn gears shafts and bearings which will normally be replaced during rebuilding. On occasion a gear tooth may be chipped or broken due to a missed shift. The transmission case should be drained and cleaned of any pieces as soon as possible to prevent further damage from the pieces being picked up and meshed into the gears with disastrous results. Worn gears with tapered tooth faces will tend to push the gears out of mesh while under load and in the shift rail detent plunger spring is weak or broken it will pop out of gear quite easily. The best solution here is prevention by careful restoration of the whole assembly. The universal joint sometimes can come loose from the rear shaft due to a weak lock washer on its retaining bolt. Always use a new lock washer when assembling a u-joint to the transmission.

Not too many differential related problems are experienced on the road other than abuse due to lack of lubricant. A normal rebuild will dictate replacement of all bearings and races and seals. All gears and axles should be carefully examined for broken or worn teeth, worn keyways, cracks, and stripped threads. An axle nut that won't hold on the stripped threads can be sawed through and clamped to the remaining threads with a vise grip pliers and the car can be slowly driven to a repair site. Worn keyways can be re-cut oversize by a machine shop and a custom made ''T'' shaped key used. However, be sure to examine the axle keyway area very carefully for indications that the axle is fracturing at that point. Most often the most economical solution is a select used axle. Many replacements are so poorly made that they are unsatisfactory in use. Once in a while an axle key will be sheared in two while driving. If a spare key is not available a quick fix is to take the two halves and put them together vertically in the keyway. Not the best, but it will get you going again until a proper repair can be made.

Hubs and springs
An alarming lack of lubrication seems to be common on restored cars . In an attempt to keep the restored ''A'' clean it appears little if any periodic lubrication program is being followed. Remember the ''A'' does not benefit from the modern technology of sealed joints and must be adequately lubricated to force out the old contaminated lubricant and road grit. Brakes must be periodically disassembled and cleaned and re- lubricate with high temperature brake grease. Wheel bearings must be inspected and re-packed with good quality wheel bearing grease and the hub filled between the races with lubricant as a reserve or on-the-road problems will result with disastrous results.

For a really complete and accurate study on the operation and rebuilding of the brake system I highly recommend the film How to stop on a dime by Victor Duncan . If you haven't seen it yet have your region rent it from the National or buy it from Double D Productions. It is worth it.

Not all problems are predictable such as a broken front hub, but things like welded in studs should be avoided as the studs will usually crack loose at the welds or the emergency brake clevis pins will scrape or snag on them. This usually results in the emergency brake applying and tearing up the carrier plate. The use of an axle shim may be required but remember to periodically re-torque the rear axle nut to 90 ft-lbs to prevent movement and consequent wear on the shim and key. Careful attention to the brake lining material is absolutely essential. Use only lining with fine brass wires in it --no aluminum wires--as the aluminum wire is not compatible with the steel drum. The steel galls onto the aluminum wire and quickly forms a mass of steel impressed in the lining which scores the drum in short order. Check all linings before installation by grinding the end and look carefully for the wire color. Even some lining from Snyder's Antique Auto Parts advertised as having brass in fact had aluminum in it. Samples are shown. Brake rods are another area of problems. Most old rods should be replaced with new due to wear rust and stretching with age. However some rods seem prone to having the eye break off at very inopportune moments. On these rods the return spring swedged collar is in fact a braised on collar and is usually incorrectly located by about 1-1/4 inch. These rods are usually zinc chromate plated. The better rods, while not perfect, are unfinished but well made. The thickness of the eye end is thicker than original but can be ground to fit a worn lever.

Steering gear
There is a prolific supply of replacement steering gear parts. It is best to use good used originals or new old stock replacements if possible. However the current replacements can be used if nothing else is available and if you examine the parts carefully. Here is a comparison of a good used sector and a J. C. Whitney sector. Aside from being soft due to no heat treatment, the tooth angles are completely wrong. This is unusable! Generally the "made in Argentina" steering parts seem to work with a minimum of grinding and fitting and most of them seem to be heat treated. The addition of sector housing needle bearings and oil seals helps to retain the lubricant in the housing ant that is the reason most a steering gears are bad today--lack of fluid lubricant. Chassis grease used in the housings doesn't run out, but it doesn't follow the gears. Using the lip type seal on the sector housing and the tube and plate on the bottom keeps the fluid lubricant in the gearbox. A tube seal can even be made for the seven tooth gear by using thin wall brass hobby tubing. A $1.00 piece silver soldered to the old cork seal nut does the job nicely.

I know I haven't been able to touch on even a fraction of the trouble areas of our restored driven cars, but I hope that you have gained some knowledge and maybe can pass it on to some of your fellow Model ''A'' friends. Tips and hints that you have learned from your many experiences with the Model ''A'' may seem trivial to you but can be of invaluable help to others. Please write your ideas and suggestions down and share them with all of us through your club magazine -- The Model ''A'' News. Send these hints to the editor; Mr. Ken Keeley. He will appreciate it as will your fellow club members.

Thank you for your attention. Some of the parts used in the slide illustrations are available for your inspection here in front of the room. Feel free to come and look.


Another pretty good web page by
Grant MacLaren