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Tech Q&A - Engine - Other


My Model A is running a little rough with a lot of backfiring when you step on the accelerator. Can you give me some idea where to start looking?

Back firing is usually caused by the condenser failing or... the points may not have sufficient gap. Make sure they are set at .018 to .020". Make sure they are not burnt. Backfiring can be caused by intermittent firing of the ignition system or very lean fuel mixture. If the car has been setting for a while, the carburetor float valve may be sticking. Clean the float valve good and set the float level. Backfiring due to intermittent ignition can be caused by a frayed wire on the bottom side of the distributor plate . . or .. by intermittent connection of the ignition switch.
1.) Check point setting first.
2.) replace condenser next. Make sure the condenser you buy is the right length, some are too short, and that it is a good quality.
3.) Check that the carburetor float valve is operating correctly.
4.) Sometimes the pop out type ignition switches get intermittent. As a last resort, replace the ignition switch/cable.
-- Les Andrews, Technical Director


Just looking for some advice on starting a '29 Sedan (of which I know nothing about) It was my grandfather's car and has been sitting unused for 15 years. Prior to his passing, it was driven on a regular basis. How do I set the spark control for start up? What fluids should be changed etc... I just need to put it on the trailer, off the trailer and into my garage. I would eventually like to drive it on occasion. The tires are still holding air. Any suggestions would be appreciated. -- CA LINDLEY

Here's a list of the steps you should take. Also consult the "Model A Instruction Book" which was included in the original tool kit. Reprints are available from your local Model A supplier.

  1. Change the oil before starting the car. Use 30W non-detergent.

  2. Check transmission fluid level. Fill to just below the fill spout on the right side of the transmission. You will have to remove the floor boards to get to it. Use 600W oil or straight STP.

  3. Check radiator water level. 1" below filler neck.

  4. After sitting for 15 years you may have gummed up gasoline in the gas tank. There is a gas shut-Off valve under the gas tank just above the emergency brake handle. Turn the handle on the shut-off valve up to the horizontal position for shut-off. Disconnect the gas line at the carburetor and then open the shut-off valve to see if you get a good flow of gas out. Reconnect gas line.

  5. Make a couple of primary checks before trying to start: Model A has a negative (-) 6 volt system. Place a piece of paper between the point contacts. Turn the ignition key On and check for 6 volts from the Point arm to a ground point. (- or ground lead of the volt meter to the point arm). If 6 volts is present then remove the paper from between the points and then pull the point arm open and closed to see if a spark is generated. If it is, you are ready to start the engine. Turn the key OFF.

  6. Turn On the gas shut-Off valve. Turn handle down (vertical position).

  7. Turn the choke knob CW until it seats then CCW 1/4 turn.

  8. Place the left (Spark) control rod full up (retard position).

  9. Place the right (gas) control rod full down. --- MAKE SURE SHIFTER IS IN NEUTRAL POSITION----

  10. Turn on ignition key, pull out the choke rod and hold and press the foot starter. After about two revolutions let go of the choke rod and the engine should fire and start. As soon as it starts, move the spark control rod about 3/4 way down and move the right control rod ( gas) up to an idle position. Both control rods can be left in that position for normal driving.

-- Les Andrews, Technical Director


What precautions do you recommend before starting a rebuilt engine for the first time or an engine that has not been run for many months or years?

When the engine first starts, you want adequate lubrication to all engine parts, particularly the rods, mains and rings. This requires that there be oil in the valve chamber to provide lubrication for the mains and the cam shaft bearings and in the oil pan tray which provides lubrication for the rest of the engine. The only way to be sure of this is to drain a couple of quarts of oil from the oil pan and pour it down the distributor mounting hole.
-- Lyle Meek, Technical Director


My question of the day relates to fitting exhaust manifolds and gland rings. I have tried to install three different original manifolds onto gland rings without any success. Although the rings will fit into both the manifold and the block, the alignment for putting them all together is way off. What is the solution to this problem? Many thanks for your assistance. -- Kirk Mohney, Gardiner, Maine

Ford had the same problem or recognized the problem. That is why the gland rings were eliminated in Jan 1929. He went to a copper clad manifold gasket . Make sure your intake manifold and the exhaust manifold have been machine surfaced together so they are the same height. Throw the glands away and use the good quality copper clad asbestos gasket and you won't have a problem.
-- Les Andrews, Technical Director


I recently bought a 1931 AA truck for restoring and was wondering what horsepower these engines came in? Are they any different from engines produced in automobiles? -- Bob Pearson

The truck engine is the same as the Model A car engine. The torque power for the trucks was obtained through changes in the transmission and differential. All Model A engines were rated at approximately 24 Horsepower (SAE) or 40 Braking Horsepower.
-- Les Andrews, Technical Director


I have been working on the '29 "A" Coupe but hit a glitch on the front motor mount. Removing the front bolts from the motor mount and the yolk stud lower hardware and raising the front of the engine slightly, the yolk should fall forward and be removable from under the crankshaft pulley by moving forward and up. It seems logical, but it doesn't happen that way in my car. I raised the front of the engine up (loosened the rear mounts some) to the point where the throttle linkage was just touching the firewall and I still couldn't get the yolk out from under the crankshaft pulley. What am I doing wrong?? I wanted to replace all the parts and pieces and repaint the yolk and cross frame. I had to settle for leaving in the old spring mounting plate which looked OK and splitting the leather washed to get it around the stud and under the yolk collar (hope it stays there).

I did replace the springs (one collapsed and one broken in half) and all the bottom brass bushing, spring and castle nut hardware. Also, I noticed that when the motor mount spring apparently broke the front of the engine had dropped enough to hit the pulley housing on the front cross frame and wear a little grove in the shaft part of the pulley housing. Doesn't seem like anything to worry about for now. However, is there some other hidden damage I should look for?? Should I replace the pulley immediately?? When I do replace the pulley, do you recommend the two piece or the webbed one piece?? Also when replacing the pulley, should I replace the upper and lower "dog turds" with original design or move into the one piece neoprene seal they now have available and say it does not require any engine modification??

You must remove the crank pulley to get the front motor mount off. Here is the advantage of a two-piece pulley. Two-piece means the pulley shaft that slides on the crank is in two pieces. This is strictly after market. Ford never made it this way. The advantage of having the shaft in two pieces is it will allow the pulley to be removed from the crank shaft without removing the radiator. There is only a little over 2" clearance between the pulley and radiator. The standard pulley and shaft is 3-1/2" long. The two-piece pulley is 2" long and the separate shaft portion is 1-1/2" long. They are notched so the two pieces lock together when bolted in place. Therefore, the front pulley section can be removed without removing the radiator. With the standard pulley you must remove the radiator to get clearance to pull it off the crank. The pulley nut takes a 1-3/8" socket if original Ford. Three replacements have been used over the years. I suspect they are from different year or make cars but have the same thread size for crank. These socket sizes are 1-1/8", 1-1/4", and 1-5/16". Check your size before buying a socket. All should have the cast iron sprocket design.

Another caution with some of the two-piece pulleys. A slot is cut into the back end of the pulley shaft and fits into a key on the crank, locking the pulley to the crank. Some of the pulleys slide too far onto the crank shaft. This allowed the end of the crank shaft to stick out beyond the end of the pulley casting by .010" or more. The end of the shaft MUST stop short of the front face of the pulley. This allows the ratchet nut to firmly tighten against the face of the pulley and pull it tight to the crank. If the crank sticks out beyond the pulley face any amount, the ratchet nut can not be pulled against the pulley, and the pulley will be loose on the crank shaft.

My recommendation : Replace the pulley if it has any defects in it. I have seen these blow apart many times when on the road. It's easier to fix in your garage then on tour. It's ok to go with the two piece pulley (two piece shaft) but get a good quality one. Then make sure it fits correctly. The advantage is if the pulley blows when on the road, you can replace it with out removing the radiator. If the two sections are not fit extremely tight (with the ratchet nut) it will make a clicking noise like a loose tappet, where the two sections are notched together.
-- Les Andrews, 1998 Technical Director


I have a 1930 four door sedan recently purchased. There is a very strong odor of oil entering the car after it heats up. Does it come from the oil breather? If so, is there a way to deflect the exhaust under the car so that it doesn't smell up the inside? Thank you.

Sounds like you have a very tired engine. What you are smelling is cylinder blow by caused by worn out rings and worn cylinders. The combustion chamber is leaking past the rings into the crankcase and being blown out the oil breather pipe. You can minimize the amount that gets into the inside of the car by putting a flexible breather pipe tube on the breather pipe to replace the cap. This is an accessory that has a flexible pipe that is about 24" long to route the blow by under the front floor boards. This may help some but will not eliminate the problem. An engine rebuild is the only solution. In the mean time use 40W oil and add some STP to thicken the oil around the rings and get a little better seal. This is not a fix, just a temporary band aid. Good Luck.


A question about the starter drive (this would be much easier if I could draw a picture!) Starting at the end of the shaft there is a piece that holds one end of the drive spring and is pinned to the shaft by the bolt. It is cut so that a tab mates into the end of the rest of the drive. It is this second part, that has the center cut to accept the tab, that I have the question about. It is in two pieces and the separation appears to be a break and not manufactured that way, but it also has a groove and a thin retaining ring which holds it together. If it was one piece it would not fit over the end of the main part of the drive. So - is mine broken or just worn. It was working fine before removal. --Cary Taylor, Alameda CA

It sounds like you have a broken drive sleeve or service sleeve. In the Ford Service Bulletins, page 577, you can find a partial description of the service sleeve and drive head. A full description of how it all goes together is found in the Model A Ford Mechanics Handbook, page 1-21 and 1-22 with full illustrations. Spring clips were a service item used under the two bolts. If that is what is broken you can discard and no need to replace. But it sounds like you have a cracked Bendix drive sleeve, in which case it will have to be replaced.
-- Les Andrews, Technical Director

Last Updated: 04/01/2012