Technical Tips
Every owner should have a copy of the factory service manual for your P15 or D24. Even though you may not work on the car yourself it provides your mechanic the necessary information to properly service and maintain your car. You can bet he won’t have information in his shop covering a 50 year old car. For those of you who do turn a few wrenches, which I feel is one of the best reasons for owning a 15 or D24, this section covers some common questions ranging from general maintenance to engine overhauls.

Lug Nuts
Lug nuts on your P15-D24 don’t always follow the righty-tighty, lefty loosey rule. Lug nuts are tightened in the same direction as the wheel rolling forward. Why were the lug nuts set up this way ? It is a safety feature ! The idea was any momentum transferred to the lug nut from the wheel turning would always be in direction to tighten the nut. So, on the drivers side wheels, you turn counter clockwise to tighten the lug nut (Lefty-tighty !) It you look closely on the lug bolt or stud you will see a "L" or "R" stamped on it. So when you are doing a brake job, don’t get the drums mixed up. If you are having the tires serviced be sure to warn the shop about the reverse threads, as they have probably never seen a car with lug nuts like this. Also, ask then not reinstall the nuts using an air gun. It is very easy to strip a reverse pitch thread in the wrong hole using an air gun. If they use a manual torque wrench it is pretty hard to screw up.

Valve Adjustment
Proper valve adjustment is critical for quiet and efficient operation of a flathead six, and also the first line of defense against burned valves. Compared to todays overhead valve engines, the flathead is a very simple design. A tappet follows the contour of the cam lobe pushing a valve up and open at the appropriate time. The only adjustment is the clearance between the tappet and valve stem. Accurate adjustment can only be made while the engine hot. To complete the job you will need a valve gasket set, set of go/nogo feeler gauges, pair of tappet wrenches and a pair of gloves to protect you from burns on the exhaust manifold.

While the valve covers are readily visible from the top of the engine, don’t attempt this job from above the manifold. Instead raise the right front side on a jackstand and remove the right front tire. Inside the wheel well is an access panel approximately 3 feet wide and 18 inches high. Remove the bolts which hold the access panel in place, using plenty of Liquid Wrench. They have probably not been removed for quite a few years. You will now be looking directly looking at the valve covers. Start the engine and bring it up to operating temperature. After the engine warms up, stop the engine and manually turn it over to Top Dead Center (TDC). Verify piston #1 is in firing position by checking the position of the distributor rotor. If should point around 7 o’clock. If it points to the 1 o’clock position, you have piston #6 in firing position. Manually turn the engine one full revolution and you are ready to start. Remove the valve covers and use the following sequence for the order of the valves to adjust.

Exhaust valve clearance .010
Intake valve clearance .008

Stage A, #1 and #6 at TDC, #1 in firing position
Stage B, #1 and #6 at TDC, #6 in firing position

Stage A - Adjust
#1 Both valves
#2 Inlet valve
#3 Exhaust Valve
#4 Inlet valve
#5 Both valves

Stage B - Adjust
#2 Both valves
#3 Inlet valve
#4 Exhaust valve
#5 Inlet valve
#6 Both valves

Using the two tappet wrenches you can use one hand to adjust the tappet, leaving the other hand free for the go/nogo gauge, The gauge has three steps cut into it. If the adjustment gap is too wide, you will be able to slide it to the third step. If the gap is too narrow only the first step will slide between the valve and tappet. What you want is the middle step to fit snugly. Adjust each valve as specified in the adjustment sequence. It is better to err on the side of too much clearance versus not enough. Too much clearance may result in a slightly noisy tappet, while too little may burn the valve. After you finish the adjustment, reinstall the valve covers with the old gaskets. Bring the engine back up to operating temperature and you will notice the engine is much quieter. Sometime you will need to readjust a single noisy valve. Just make sure it is fully off the cam lobe and totally closed. If everything is OK remove the valve covers and install the new valve cover gaskets (780-469) with sealer. When re-tightening the valve covers don’t go overboard. They just need to be snug, letting the gasket and sealer do the work. Too tight distorts the sheetmetal cover and usually results in leak. Reinstall the access panel and tire and you are back on the road.

Properly adjusted valves result in a quiet running engine and help protect against damaged valve train components. If you have done the job right it will be difficult to tell if the engine is running from five feet away because it so quiet !

Evr-Dry Kits
Evr-Dry kits are rubber boots which enclose the spark plug and wire, creating a waterproof enclosure. Looking at the hood you will notice a seam alone the center of the car, directly over the spark plug wells on the cylinder head. Rain water can seep through the seam and drip down onto the plug wires, often filling up the shallow plug wells recessed in the head. Then when you try to start the spark plug wires are shorted by the water. Also water drips onto the distributor cap with the same result. Evr-Dry kits are the solution and will keep you going rain or shine. The kit consist of a small metal lipped cup which sits under the spark plug, rubber boots to cover the top of the spark plug and distributor cap terminals, new plug wires and brass connectors. Installation is a simple 30 minute job. Separate the new plug wires by length. After removing the spark plug, place the metal cup under plug and screw the plug back into the head. A Plymouth Product Information Bulletin indicates you should remove the spark plug gasket. The metal cup acts as a washer and correctly positions the depth of the plug electrode in the head. Next remove the old plug wire from the distributor. Push the new plug wire through the Evr-Dry boot, and install the brass sparkplug terminal. Depending upon the terminal design, you may need to strip the plug wire back a 1/2 inch, then crimp the terminal in place. Push the terminal onto the spark plug and mount the boot on the top edge of the metal cup. It is now watertight. Feed the other end of the new plug wire through the distributor wire guide mounted on the side of the coil. Push on the smaller distributor rubber boot. Finally install the brass distributor terminal and re-insert the plug wire into the distributor cap. This simple and inexpensive add on will guarantee easier starting in wet weather year round. Evr-Dry Kits are available from Robert's Motor Parts.

Evr-Dry Revisited
After several emails from P15-d24.com readers with similar experiences regarding Evr-Drys, consider this tip. More than once after installing a set of Evr-Dry and plug wires the car would refuse to start, or run poorly with a bad ignition miss. Every time this was tracked down to a connector on the plug or coil wire which did not seat properly in the distributor cap. The problem is the brass terminals. They use a small spade point which is pressed into the center plug wire conductor. However this terminal design has nothing to hold the terminal to the plug wire except the sides of the cap as you slide it in. If they are slightly off center the spade point loses contact with the center conductor. One P15-d24.com visitor had a simple fix. NAPA sells replacement plug wire terminals and the design allows you to securely crimp the brass terminal to the wire. Discard the terminals which came with your Evr-Dry kit and use the more secure NAPA terminals.

Hard Starting Hot Engine
One of the most common complaints is hard starting when the engine is hot. Usually the starter will just grind away but won’t fire. Usually after about 15 minutes when the engine has cooled down, the car starts immediately. Generally the problem is caused by vapor lock, that is the fuel getting so hot in the fuel line it vaporizes or builds pressure and floods the carburetor bowl. The culprit is heat, specifically from the exhaust manifold. The Chrysler engineers addressed the problem when building the car. However the appropriate equipment has been lost or modified over time, causing the problem to reoccur.

First, your fuel pump should have a flat heat shield installed between the pump and manifold. It is held in place with a bolt on the manifold and tall bolt to the fuel pump. It is very common for this part to be lost when the fuel pump was replaced. If it is missing reproductions are available from Paul Taylor Industries, PO Box 618, Arroyo Grande, CA 93421 for a reasonable cost

Second, is your heat riser system working correctly ? If it is preheating the fuel mixture all the time it will just contribute to your hard starting problem. Check the heat riser section for more information.

How far is the fuel line from the exhaust manifold? If it is less than one inch from the exhaust manifold, replace the line. Relocate it away from the exhaust manifold. Do you have an aftermarket fuel filter installed on the line ? This is not a good location as it provides more area to absorb heat. And NEVER use a plastic fuel filter. Under heavy engine load the temperature will get high enough to melt the outside of the filter case, allowing fuel to be sprayed directly onto the hot engine.

Next check the carburetor float and make sure it is correctly adjusted. It the float valve is out of spec, it can make the carburetor much easier to flood

If you still have problems after checking these items you can try a couple inexpensive modifications. First, install a Carburetor Anti- Percolation Spacer from Phillips Performance (360-652-3595). This insulates the carb from the heat in the manifold.

Lastly, insulate the fuel line. I have used small rubber hose split in the middle, wrapped the length of the steel line with good success. Insulation products made specifically for this purpose are also available from aftermarket suppliers.

Hard To Start When The Engine Is Cold ?
(Plymouth with manual choke)
Try this tip. Pull the manual choke out 3/4 to 1 inch. Pump the accelerator once or twice, then hit the starter button. Just setting the choke doesn’t always set the linkage on fast idle ramp. Pumping the pedal sets the fast idle and you should start right up.

Crankcase Ventilation System
The crankcase ventilation system on your flathead six is simple to check and maintain. Its’ job is to clear the crankcase of unburned fuel and moisture to prevent sludge forming in the crankcase oil. This is accomplished by bringing in fresh air through the oil filler cap and tube. Under the exhaust manifold a downdraft tube creates a vacuum as you drive down the road, pulling gases and moisture out of the crankcase.

The recommended maintenance includes cleaning the filter in the filler filter cap with kerosene. Perform this with your oil changes. After it dries, recoat the filter material with engine oil. Go easy with the oil, 5-10 drops is fine, or you will be wiping it off your distributor and oil filter for the next thousand miles.

Make sure the orientation of the cap is correct. The open filter area should face the rear of the car. The maintenance instruction decal should be visible on the side of the filler cap. The keyway in the oil filler cap fits over the ridge pressed in the oil filler tube. Turn the oil filler tube so it allows the correct orientation of the oil filler cap. If the open filter area is facing forward, the engine fan will blow more dirt and dust into your oil. You may need to adjust the two flats springs inside the cap for easier removal. When everything is set up correctly, the cap will come off easily without pulling the oil filler tube out of the block.

Last check the downdraft tube under the manifold. Even though most illustrations show the tube positioned vertically, visitor Bob Douglass forwarded a Plymouth Service Department flyer stating "It is important that this pipe (ventilator outlet pipe) be returned to its extreme rear position... If this is not done and the ventilator pipe is left in forward position, dust will enter the engine oil pan, causing rapid wear of moving parts." This extreme rear position maximizes the vacuum effect created by they air moving past the tube, thus pulling the gases out of the crankcase. Make sure the tube is not damaged or partially blocked by oil sludge. It is attached to the block by one bolt and is easily removed for cleaning or repair.

Keeping your crankcase ventilation system correctly operating will improve the life of your oil and general engine life. Just remember to check it with each oil change.

Rear Brake Drum Removal
Unlike most "modern" cars, rear brake drum removal requires a special brake drum puller. Fortunately, these pullers are available at most automotive tool rental shops. This is one tool buying may be a wise investment if you plan to work on you P15-D24 on a regular basis. Most tool shops rent them for $30 to $40 a day, while you can purchase one for about $125 dollars.
To remove the drum, jack up car and place on jackstands. Back off the "minor" brake adjusters using a 3/4 inch wrench on the back of the backing plate. The wheel must turn freely. Next, remove the axle cotter pin and locking nut. An air gun is very useful for breaking the nut loose. You may loosely re-attach the axle locking nut. This insures the drum won't fly off the axle when it breaks free. Attach the puller to three of the lug nuts and snug the puller against the axle. Using a large hammer or mallet strike the puller arms until the brake drum breaks loose. An air gun can be used instead of a hammer on the puller adjusting nut. Slide off the drum and be sure to remove and save the square steel key. I have seen newsgroup posts recommending heating the drum to help break it loose. I have never needed to heat a drum and do not recommend it. It is very difficult to control the heating and you may cause serious damage to the underelying components such as axle seals or wheel cylinders. Usually the drum is stuck because the brake adjusters are not fully backed off.

Before re-assembly you might consider adding some lubricant to the rear axle inner bearing.

Re-assembly is easy. Put a very light coat of grease on the tapered axle. This will keep the drum from rusting to the axle in the future. Slide the drum on, aligning the keyway on the drum and axle. Carefully drive the square key back in with a hammer. Tighten the locking nut to 120 Ft/Lbs torque and insert a new cotter pin. Adjust your "minor" brake adjusters and remount the tire. Revised 11/19/99.

The Heat Riser Advisor

The heat riser system diverts warm exhaust gases to a chamber inside the intake manifold. When the engine is cold, the valve is held closed by a thermostatically controlled spring. The hot exhaust gases preheat the intake air, enhancing drivability during warm up and cold weather. As the car warms up the thermostatic spring controlled valve opens, reducing the amount of warm air being diverted. At wide open throttle, the valve opens automatically, allowing the exhaust gases to pass straight to the exhaust system.

The heat riser is an import part of the fuel system. A valve stuck in the open position causes problems such as slow warm up, carburetor icing, stalling and flat spots during acceleration. Another serious problem is the potential for crankcase dilution caused by excessive choke during starting and warm up. A valve frozen in the closed position is just as detrimental. Common problems include hard starts when hot, detonation (pinging under load), overheating, burned valves and a warped manifold.

Regular maintenance of the heat riser should be on your monthly checklist. With the engine cold, inspect the counterweight, looking for a broken return spring. The unit should easily turn clockwise, then snap back to the upright position when released. If it sticks or is frozen, try carburetor cleaner or Liquid Wrench to looses up the carbon. Don’t lubricate the shaft with motor oil. It will burn, causing additional carbon buildup. If none of these work plan on spending a Saturday afternoon to remove, overhaul and reinstall your manifold. Plus you will need to make a trip to your local welding shop.

Before you get started, make sure you have the following parts:
Heat riser repair kit, including shaft, bushings (2), diverter valve and spring.
Some kits include a new stop, counterweight and spacer. You can use your old parts if these are missing.
Manifold gasket set (780 460)
Exhaust gasket (679 023)
In addition, you will probably need to replace the nuts and bolts for the exhaust flange (7-16"-20 pitch x 2"), brass nuts for the manifold studs (3/8" x 24 pitch), four bolts (5/16"-18 pitch x 2-1/2") which hold the manifold together.
Repairs typically address problems such as a frozen shaft, missing diverter valve, broken thermostatic return spring, or the entire assembly missing! Also, it is common for the gasket to fail between the intake and exhaust manifolds, resulting in an exhaust gas leak. The repair procedure is covered in the service manual but here are a few tips.

Before disassembly, drain your coolant. When you are removing the manifold nuts it is quite common for the stud to back out of the block. Many are tapped into the water jacket and when they come out your coolant leaks out. After you unscrew all nuts the manifold should slide off with some gentle persuasion. If not, STOP ! You have probably missed a nut. The total count is 13 nuts, with one under and behind the heat riser. This one is usually missed. You can, with some difficulty, reach it from above. It is much easier to remove the front passenger wheel to reach the wheel well valve adjustment access panel. Once this panel is removed the nut is within easy reach. In addition, now you can use your torque wrench to properly re-torque everything when you reinstall the manifolds. Also, you may need to loosen all the nuts about a half inch, then slide the manifold assembly out the half inch before you can remove the nuts.

Be sure to use plenty of Liquid Wrench when removing the bolts which hold the exhaust and intake manifold together. My luck has been about fifty-fifty in removing the bolts without breaking. When they do break all is not lost. First, try to carefully drill out the old bolt, then run a tap to clean up the threads. If that fails, use a helicoil kit and install the helicoil per the manufacturer instructions. I have had success using both approaches.

When you reassemble the manifolds you might consider using stainless steel bolts. I have found the different metals, along with an anti-seize compound, make it much less likely to freeze together, making future maintenance easier. Also make sure you use the correct length for the bolts. The parts book calls for 5/16"-18 pitch x 2-1/2". Too long a bolt will not allow the gasket to seal along the intake and exhaust seam resulting in an exhaust leak. Also an overly long bolt may crack the intake manifold as you torque it down.

Verify the replacement shaft for the diverter valve is the same length as the one installed. Some kits provide longer shafts, which work on the larger 250 cubic inch flathead six, which if used unmodified, will cause the counterweight to miss the stop post on the intake manifold.

Remove the old bushing with a drift punch if possible. If they refuse to budge, drill them out with an appropriate sized bit. Be sure to install new bushings with the new diverter valve shaft. I use the new shaft as a guide for the bushings, seating them with a rubber hammer. After you have installed the new bushings verify the shaft turns freely. It they have any binding, take the assembly to a machine shop to have them hone the new bushings. Any binding will cause the heat riser valve not to work correctly.

When mounting the valve to the shaft, be sure it sits on the top of the flat cutout in the shaft. It is easy to get it on backwards. Check the shop manual if you are not sure about the correct orientation. If you repair kits provides a shaft with two tapped holes, use the provided machine screws to attach the new valve plate. While the screws will work, I recommend also having the valve spot welded to the shaft. It will cost a few bucks but the valve won’t fall off in a thousand miles. I have never seen one separate from the shaft that was welded.

When attaching the spring and counterweight be sure to wrap the spring the correct number of turns and in a counterclockwise direction. It should be wrapped 335 degrees. Also check the valve alignment to the counterweight. When the counterweight is a 12 o’clock the valve is closed (or in the up position), diverting hot gas into the intake manifold heat chamber. When the counterweight is in the 3 o’clock position, the valve should be open, allowing the exhaust gas to pass straight through the manifold to the exhaust system.

The service manual covers the reinstallation procedure but just few reminders. Use a die to chase the threads on the studs before re-assembly, and replace any studs where the threads are not in good shape. Also you might consider replacing the steel nuts with brass, except for the locking nuts used on the exhaust manifold at cylinders 1 and 6. Leave the 2-1/2 inch bolts which joins the exhaust and intake manifolds together loose until you have mounted the manifold back on the block. Use new gaskets. Snug the manifolds against the block, then tighten the two manifolds together. This insures proper alignment of the entire manifold against the block preventing exhaust or vacuum leaks.

Also make sure you put the proper nuts and spacers on the correct studs. The exhaust manifold tubes for cylinders 1 and 6 have special spacers and nuts. The spacer is concave on one side and this faces out toward the nut. The nut is split on one side. This faces into the concave surface. As you tighten the nut is compressed by the spacer, locking it in place. The manifolds by cylinder 3 and 4 use a wide flat spacer. Torque manifold stud nuts to 15 to 20 foot-pounds.

After installation test the operation of the heat riser. With the engine cold and not running you should be able to move it forward almost 90 degrees, release and have it snap back to the upright position. Start the car, and rev the engine. The counterweight should again move forward as the force of the exhaust gas causes the valve to open and exit out the exhaust system. The counter weight should return to the upright position when the engine drops back to idle. Check the spring resistance of turning the counterweight. (wear gloves, it will get very hot ! ) As the engine warms and the exhaust manifold heats up, spring tension should lesson, divert less hot gasses to the heat chamber.

A properly operating heat riser system makes your car easier to start, improves drivability and reduces engine wear. A monthly check of its’ operation will insure a longer operating life for your flathead.

Water Distribution Tube
The water distribution tube provides a vital function in cooling your engine. It directs cooling water in the upper block and valve area. Generally it is removed for inspection when an engine is overhauled, and replaced as required. However, in my experience, many production rebuilders do not perform this repair because the tube is rusted in place and difficult to remove. Failure to replace a rusted out water distribution tube will certainly lead to hot spots in the block and future problems. Replacement water distribution tubes are readily available from many NOS suppliers, manufactured in either steel or brass. Be sure you order a tube for a Plymouth or Dodge. The ones used in DeSoto or Chrysler look similar but are designed to fit the larger blocks found on those cars.

Access the tube by removing your water pump. If you are doing a rebuild, access is straightforward. If you are trying to do this in the car you will need to drain the coolant, remove the radiator, fan and water pump. Looking at the block face, it is the "D" shaped opening on the left, almost in line with the valves. Using a hook formed from 1/2 inch steel rod, insert the hook and catch one of the slots cut into the upper edge of the tube. This is not an easy repair to do with the engine block in the car. If you are really lucky, a sharp pull should break it loose and the tube will slide out. I you are like the most of us, it won’t come out. Next step is to liberally apply a lubricant like Liquid Wrench or motor oil along the edges of the tube. I flip the engine block upright, and this allows the lubricant to run down the sides of the rusted tube. Let it soak for a while and give the hook another try. If you are having trouble getting the hook to stay set in the tube hole, try squeezing the edges of the tube together with a pair on needle nose visegrips. You can generally collapse the tube sides inward 2 – 3 inches and this provides a firm griping for the vice grips to hold onto. A small slide hammer can be hooked on to the visegrips and a couple swings on the slide hammer pops the tube out. Still no go ? Take a piece of 1/2 wide flat bar stock and gently drive it into the block between the thin straight side of the tube wall and the block. Again, use plenty of lubricant like Liquid Wrench or motor oil. You are trying to break loose the rusted tube wall from the block. Usually the tube collapses inward a bit, making it easier to remove. Drive the bar stock in 6-8 inches, then try the vice grips and slide hammer. If this doesn’t work, try driving the bar stock in a little deeper until you can finally remove the old tube. I have used this technique on four different blocks with success. If it is not moving, be patient and let the oil soak overnight. Give it a chance to loosen up the rust bond between the tube wall and block.

If you are really unlucky, the tube will break and only a section will come out. I have not had this happen, but have seen it mentioned in the service manual. Slightly sharpen the edge of the bar stock so you can catch and lift the remaining tube pieces away from the block side and again lubricate well. I think you will need a stronger hook to catch the remaining tube pieces. In my experience it was very easy to pull the hook out of the 1/4 inch rod stock when trying to pull the tube. A heat formed hook would be the way to go. If you are doing a rebuild, cleanup is easy. When they hot tank the block it will remove the lubricant from the water jacket. It the block is in the car, rinse well with a soap solution, then flush the water jacket until the water runs clear.

Installation of the new distribution tube is straightforward. Inspect the block to make sure the water jacket is clean. If not flush and clean. The new water distribution tube is slid into the opening and then the front D shaped edge gently peened over to hold it in place. Reinstall the components you removed and refill with appropriate coolant.

New ! Water Distribution Tube Tip
Visitor John Moschinger had a great tip to help remove a badly rusted water distribution tube. After you have removed the flathead note the row of manifold studs drilled through to the water jacket. Once the studs are removed penetrating oil can be applied through the holes directly onto the sides of the rusty distribution tube for the entire length of the tube.

Convert Or Keep The Faith, 6 or 12 volts
A common topic of discussion for P15 and D24 owners regards conversion of the original 6 volt systems to a "modern" 12 volt environment. While such a project is technically feasible, it’s a good idea to review both the objectives and issues of a 6 to 12 conversion project.

The first question is why. Common answers include "the lights are dim", "faster cranking to start easier" or " I want install a Cassette or CD player". Some owners feel a 12 volt system is "safer and more reliable" or "easier to jump start if the battery is dead."

Lets look at these issues and balance it against what you face if you decide to convert. Your author is firmly in the "keep the faith" school. Conversion, as you will see, has a whole set of issues and ultimately reduces the show and resale value of your car. When these fine automobiles were built, headlights were bright and in 1948 the weather was just as cold today, and the cars started. A poorly maintained 12 volt will be just as problematic as a poorly maintained 6 volt system. Dealing with the core maintenance problems of your 6 volt systems will usually eliminate the reason for contemplating the switch to 12 volts.

Still not convinced? Well lets look at the potential impact of switching from 6 volt positive ground to 12 volt negative ground.

First the good news. Six volt systems required greater amperage for the same load as 12 volt systems, which means the wire gauge currently installed is larger than what you would find on a modern 12 volt system. So you won’t need to rewire provided the existing wiring harness is in good condition. However, a deteriorated wiring harness is probably the most common source of electrical problems. Fifty plus years of thermal cycles have left the insulation rotted and broken, and connectors, rusted and corroded. Only a new wiring harness will fix this problem. In fact, the higher voltage potential of 12 volts will create a greater hazard and potential for fire. If the wiring harness is not in top condition, replace it. Same is true of the existing battery cables. Next you will need to switch all light bulbs including: headlamps, front and rear running lights, brake lights and turn signals. Then the turn signal flasher and dash indicator lights. Finally all dashboard illumination lights, hi-beam indicator and inside courtesy lights.

Equipment changes include: battery, regulator, generator, coil, horn relay, horns and starter solenoid. You will probably need to fabricate or buy a mounting bracket for the alternator and appropriate belt(s). Voltage reduction devices are required for non-resistive loads like the interior clock, radio, fuel gauge and heater motor. I have seen several types of voltage reduction devices, ranging from resistors to sold state devices. Pricing is in the $5.00 to $15.00 ranges, depending upon amperage. It is unlikely the ammeter could be used unmodified. Technically, the starter motor would need to be replaced, but do to the short duty cycle you probably can get by with the existing 6 volt unit.

Now, if your P15 had been manufactured with a negative ground system, you would be pretty much finished. However, P15s are positive ground, which makes the conversion much more interesting. Devices, which are on a voltage reduction device, such as the heater motor, may require positive ground for operation. If would be impossible to isolate these devices from chassis ground (I.E. "float" the grounds) and any such devices would require replacement with a negative ground device. Stock radios are most difficult because of the required antenna ground. Why not make it a 12 volt positive ground conversion? Good luck on finding any 12 volt equipment that is positive ground.

As you can see you have spent a considerable amount of money and have replaced many items with non-stock parts just to get the system to work. These changes alone would substantially reduce the resale value of the car. After making all these changes, how is it going to be more reliable?

The second and better approach is to fix what is wrong with the existing 6 volt system. Then look at few options to satisfy the objectives mentioned at the beginning of this article.

First, replace the battery and battery cables with the correct sized parts. The battery tray will hold a Group 2 battery. If you are going with a wet acid battery, most battery suppliers do not stock this size and they will try to sell you a smaller battery. Have them order the correct battery or better, replace it with one of the new dry cell Optima batteries. These put out over 650 amps, while the smaller 6 volts cases are in the 350 to 400 amp range. See the Enhancements section for more info.

Second, make sure you have 6 volt battery cables. You can bet somewhere along the way the cables were replaced and it has been my experience they will be 12 volt cables. You will probably need to order the correct cables as auto parts stores just don’t stock them.

An another option is using an 8 volt battery. This will provide a slightly higher cranking speed and brighter lights at the expense of bulb life. There is also the potential to damage existing radio equipment. In addition, an automotive electrical shop will need to adjust the voltage regulator/generator so the battery will fully charge. The 8 volt units are special order items but generally available, especially from battery suppliers who deal with agricultural equipment. If any readers have tried this approach please provide some feedback on how well it works.

Dim lights are caused by poor connections, usually a bad ground, a deteriorated wiring harness or an incorrectly installed 12 volt bulb in your 6 volt system. Switching to 12 volts won’t resolve this problem. You need verify the condition of the wiring harness, perform proper maintenance on the connectors, junction blocks and grounds and verify the correct bulbs are installed. The single most common cause of dim tail lights is someone installed a 12 volt bulb ! Check our Reference section for 6 volt bulb information.

The condition of your wiring harness is the crucial link in the chain. If you wiring harness needs replacement, changing over to 12 volts will not improve anything except the potential for a fire. If the rubber insulation is broken or cracking, replace the harness. Check with YnZ Parts of Yesterday (909-798-1498) or Rhode Island Wiring. Both are quality sources for a new harness. My personal experience with mass market "mail order" suppliers is they do not provide the correct wiring gauge for a 6 volt system, so shop carefully.

Connecting a modern sound system is problematic, but not impossible. For your stock radio, you can add FM Stereo capability to the AM unit while maintaining a 100 percent stock appearance. For a CD or cassette, use a 6 to 12 volt DC inverter. You will need to insulate the unit from chassis ground and run separate circuits for the hot and ground from the inverter to the unit. Don’t use speakers that have a common ground with the speaker leads and frame ground. Your speaker grounds need to "float". You can not use a 12 negative ground device which requires an antenna as the ground will cause a dead short. Even better, keep it simple. Buy a portable CD/cassette player.

If you have a choice, keep the faith and don’t convert. A properly maintained 6 volt system is neither intrinsically more or less reliable than a 12 volt electrical system. The system’s condition is what determines if is safe and reliable, and proper maintenance is all that is needed.

6 or 12 volts, Part 2
One P15 owner who made the switch to a12 volt system shared his experience. First he replaced the wiring, using a homemade harness. The generator was replaced with a 60 amp chrysler alternator which bolted to the original generator bracket. It did require some home made bushings as spacers. A external voltage regulator replaced the stock regulator. The original oil and temp gauges, being non electrical, required no changes. An inline voltage reducer was used on the fuel gauge. The original amp gauge, to date, has not caused any problems. It was wired only into the charging circuit. Nothing else runs off of the amp gauge. Also upgraded was the electrical service by adding a fuse panel with nine fuses. The radio and clock were upgraded to 12 volts. The heater motor was exchanged for a 12 volt motor with the same dimensions and shaft size. An extension was used on the heater motor shaft. Turn signals were installed and the original brake light is used as a "third brake light". The P15 ovwner would definitely do this conversion again as the car was very easy to re-wire.

Installing Valve Guides
If you are doing a valve job or full overhaul of your flathead six pay close attention to how the valve guides are re-installed. In the factory service manual a one liner warns exhaust valve guides are mounted reverse from the intakes valve guides (P15 Service Manual. Page 149. It is not even mentioned in the D24 Service Manual !). For exhaust valves install the counterbored ends upward. This provides better heat shielding. Intake guides are mounted counterbore down. Most machine shops are not familiar with these engines anymore and you need to warn them about the correct installation procedure.

Oil Leaks
Let me count the oil leaks: seal on the timing chain cover for the crankshaft vibration damper, seal on the transmission extension for the parking brake drum and the seal on the pinion for the rear end. Makes working under the car a messy job. Replacement of these seals is pretty straightforward, but often time consuming. Because of this, be sure to do the job right by repairing both the seal and shaft surface. Otherwise you will be redoing the job in the near future. For example, the crankshaft seal behind the vibration damper is the source of oil that blows all over the bottom of the engine. After you replace the seal check the sealing surface of the crank hub. It should be smooth with no traces of grooves or roughness. Usually you will see a groove cut by the old seal. Repair procedure for this damage use to be to braze new metal to build up the surface, then turn the hub down to the correct diameter. Good luck on finding a shop that knows how to do this type of work. Enter "Speed Sleeves". Today, you can use a speed sleeve, a very thin steel sleeve which is pressed over the damaged shaft area. This provides a factory finish for the new seal to mate against. They work great and most engine rebuilding shops have the equipment to correctly install them. They will also work on the your parking brake drum and rear end pinion seals. Installation on these parts is definitely a task to job out to your machine shop. They require a special press to install. Also the machine shop will have (or can get) the proper sized sleeve for the part to be repaired. Once completed, you can be assured you seal repair job will provide years of leak free service.

Major Brake Shoe Adjustment
Most modern brakes systems have either automatic adjusters or one manual adjuster to compensate for normal wear. However, the Lockheed designed brakes used on the P15 and D24 require additional adjustments to insure adequate brake pedal height after a brake job. Two adjustments are made, a "minor" adjustment which compensates for normal wear, and a "major" adjustment which must be done after installing new brake shoes. While the factory service manual provides considerable detail regarding the major adjustment, you must have a Brake Gauge Tool MT-19H tool. Unfortunately, these tools are impossible to find, and no one currently manufactures a replacement. So what can you do ?

First, The Plymouth Bulletin #229 (March-April 1998) has an article on how to build a low cost replacement MT-19H. You can order reprints from the Plymouth Owners Club store, and by the way, if you aren’t a member, it is a good time to download a membership form and sign up.

Another option is to use the following adjustment procedure found in an old Clymer service manual. Before beginning any major brake adjustment you need check the following items. Be sure the anchor bolts, which hold the shoes to the backing plate, turn easily. They have a locking nut on the back of the backing plate. The anchor bolt is actually a small cam, which moves the position of the "heel" of the brake shoe. Anchors have round lubrication wicks inside the washer spacer. The wicks have probably dried out over time and need to be re-lubricated. The anchor bolt head has a stamped arrow pointing to the high side of the cam. To adjust the anchor bolt you must be able turn it from the back of the brake backing plate. Remember, the brake drum will be installed, blocking access to the front side. Some anchor bolts have provisions for turning them from the back. If not, grind off two flats with a file for a wrench or cut a screwdriver slot in the treaded end of the anchor bolt. (I have had better luck using the wrench flats). Also put an identifying mark indicating the cam high point. Loosen the anchor nut and verify you can turn the anchor bolt. It is very important your brake drums be in good condition. When you spin the drum does a shoe drag in one location ? If yes, the drum is out of round and needs to be turned on a brake drum lathe. Most shops charge less than $10.00 per drum for this service and usually takes only a couple hours. It is next to impossible to correctly adjust the brakes with an out of round drum. Drums in good shape ? Then your ready to start.

1. Turn the cam nut (minor adjuster) so shoe is fully retracted inward.
2. Turn anchor bolts so both arrows are facing each other. With 2 wheel cylinders, the arrow faces the corresponding wheel cylinder.
3. Install the brake drum and tighten retaining nut.
4. Identify the wheel cylinder/shoe configuration. Note adjustment direction for the cam nut and anchor as mentioned in the service manual. Or check the P15-D24 Brake Helper. Remember the direction to decrease clearance between the shoe and drum.
5. Turn anchor until shoe "heel" drags on drum.
6. Next turn the cam nut (minor adjuster) to bring shoe "toe" into drum contact. This will cause shoe "heel" to lose contact. You need a light touch for this step. It is easy to go too far with the cam nut and overshoot, locking the drum with the minor adjuster.
7. Turn anchor again direction of arrow until shoe "heel" drags on drum again.
8. Repeat step #6.
9. Repeat step #5 and #6 until cam nut adjustment no longer frees the shoe "heel". Tighten anchor bolt nut and reinsert a cotter pin, if used. My experience with new brake shoes is it only takes 2-3 passes and the shoe is adjusted.
10. Repeat procedure for all shoes

Rear Axle Lubrication
The factory recommendation is every year or 10,000 miles. However, before you perform this maintenance you might want to take little extra time find out what is really going on behind your brake backing plates. It could save you an expensive on the road breakdown. And it is one of those jobs you only need to do once, then maintenance is easy. In working of three different cars, I have seen quite a range of axle bearing conditions. One car had no grease behind the bearing and only a small amount in the bearing. Another had at least 4 different types of grease, all stratified into multi-colored layers. The top layer was white lithium grease, inappropriate for the job and leaking past the outer seal onto the brake shoes. The third had packed grease, probably from 1948, as it required quite a bit of effort to dig it out. The point is you don’t know what previous owners have done, good or bad. Take the time to pull the axle bearing, then check the axle inner seal and bearing race. Also check axle vent to be sure it is not clogged with dirt or old oil. Once you have the axle pulled, clean out all the old grease on the bearing and recess behind the bearing. Recoat the recess with a layer of grease, and repack the bearing. Use the correct grease for the job. Make sure the filler plug on the bottom side of the axle is a bolt and NOT a zerk fitting. If you use a zerk fitting you can over-pressurize the bearing, causing the seal to fail and spread grease to the brake shoes. Write down what kind of grease you used and put the information in the glovebox. Next year or 10,000 miles later you will be glad you did.

Temperature Gauge Sender Unit Replacement
By Jim Leman
Editor, The P-15 Driver

Replacing the temperature gauge unit on your P-15 is a service best undertaken when you are in a patient mood. As with most jobs requiring work under the dash, this task will test your patience.
You will want to replace a broken or defective temperature gauge sending unit because without it you’ll lack information of a critical aspect of engine operation – water temperature. Temperature gauge sending units fail for various reasons, often from kinks or breaks in the capillary tube. This tube is inside a coiled outer protective wire shield running from the sender bulb to the gauge unit itself.

Replacement units can be purchased from any well-known Mopar parts suppliers, both those who market through catalogs, the major old car publications, the Mopar car club periodicals and occasionally they can be found both used and NOS as swap meets. Depending on where you find one – and from whom – expect to pay from $40 to more than $100. Inspect the unit carefully, especially the sender capillary tube for kinks and breaks. Test the unit before you install it in your car. Fill a glass or cup with water heated to a predetermined temperature, say 180 degrees, and insert the bulb unit into the liquid. The gauge needle should begin to move slowly and settle on or very close to the gauge face temperature marking that corresponds with the known temperature of the water. If the gauge is working right, let’s head to the garage.

Get to know the project
Open the car hood and place your fender blanket and tools on the driver’s side fender or bring your tool cart to your side. Hang your shop light so it illuminates your work area brightly. Disconnect the battery’s ground. Drain the coolant by opening both the radiator and block petcocks. If you don’t, coolant will run out onto your clean shop floor when you remove the old temperature bulb from gland nut in the side of head. You’ll find this gland nut in the left (driver’s side) of the head nearest the firewall. The bulb sits inside a tapered, threaded part known as the radimeter gland nut. The nut is a threaded into the head. To remove the old nut, use a little penetrating oil to ease your effort. Loosen it and back away the retainer and then slide the bulb carefully free of the nut. Clean all threads. To reinstall, reverse this procedure. When the retainer is tightened against the gland nut, it will secure the bulb and prevent coolant from leaks. Use thread sealer for insurance.

Getting set up
Here’s a helpful hint on positioning yourself for removing the gauge unit from the dash. P15-D-24.com webmaster Gerald Koldjeski suggests that you position yourself in the passenger compartment like slat, head and torso under the dash with legs and feet over the back of the front seat. Before you get into position though, first pull the throttle knob out full. This will depress the accelerator pedal. Place a rag or old tee shirt over the pedal to provide a cushion for the back of your head when you’re in position. Make sure you get all your tools in position first too. Hang a shop light (I prefer the cooler florescent type) so it illuminates the underside of the dash. Having two lights carefully positioned will help to eliminate or reduce the harsh shadows you’ll get under there with just one light in action. Position the tools you’ll need on the floorboard or on the front seat where you will be able to reach them when in position. The tools you’ll need include a flashlight, a long shaft slotted screwdriver, preferably a magnetized one. Leave the beer in the house.
Clearing a path
You might want to remove some underdash clutter before you start. First, remove the headlight switch. The knob removes by inserting a narrow slotted screwdriver blade into the slot on the underside. This frees the knob from the shaft so you can remove the panel nut and slide the switch free from the other side. Bag any hardware removed and label it. You may want to use tape to tape up the switch – or let it dangle free.
I also found it almost impossible to access the gauge without removing the speedometer unit first. The speedometer is held to the backside of the dash by a few screws across the top and bottom of its housing. When these screws are removed and the speedometer cable removed from the unit, you should be able to jostle the unit free and clear. Place it were it won’t get damaged.
Now, with your long-shafted magnetic slotted screwdriver, find the retaining screws in the back of the gauge and remove them. Keep the screws in a safe place.
Unfortunately, the gauge doesn’t pop free, but it too requires plenty of jiggles and a little cussing to convince it to come free of the dash. Try moving the unit up slightly and to the left (as you view it under the dash) to clear the edges of the housing frame. If it doesn’t come free after a few minutes, sit up in the driver’s seat, reach up with your arm under the dash and take the unit in hand. Move it to understand how it comes free of the dash glass – and how you must move it to free it from the housing. Remove the unit.
You’re almost done
To install the new unit, first remove the clip from the firewall grommet through which the sender wire will travel. From inside the car, with the gauge, wire and sender bulb carefully resting on your floorboard or accelerator pedal cushion, carefully push the new sender bulb through the grommet. (A lubricant like ArmorAll here eases the penetration). Now, from engine side, carefully pull the bulb clear of the grommet and with sufficient slack that it touches the gland nut head. Go back inside the car and get into position again. Carefully pull the wire and gauge unit up and through the confusion of wires and stuff behind the dash. Just as you removed the old unit from the dash, install the new one.
Use care when feeding the gauge face back into its housing so you don’t damage the delicate needle. You may need to make a paper gasket for the unit first and install it on the gauge face where it mates to the housing. When the unit fits into its housing, insert and tighten the retaining screws you’d carefully set aside.
Reinstall the speedometer, headlight switch and any other components or wires you may have removed. With the gauge in the dash and capillary tube through the firewall, insert the sender bulb into the gland nut in the head carefully securely. Use some sealer on the retainer nut and tighten against the gland nut. A firm snug – and then a nudge – is sufficient.
Finishing up
Refill the radiator with coolant and restart the engine. Check often for coolant leaks at the gland nut and both the radiator and block petcocks. Keep an eye on the gauge. I t should begin to move as the coolant warms, and it should stop when the coolant reaches the temperature allowed by your engine’s thermostat.
Replacing the temperature gauge on your P-15 takes a little time, but you can do it yourself.

Static Ignition Timing
The classic Catch-22. Your trying to get your flathead started. The engine is not running so you can't check the timing with a timing light. However you suspect the reason the engine won’t start is because the timing is set incorrectly. The solution is easy, static time the ignition.