Old car projects usually follow one of three paths. Path one is the total showroom restoration to new (or better) condition. These projects result in high point show cars often becoming trailer queens. With so much invested owners can?t afford to risk them on the open road. At the other end of the spectrum is the custom rod approach, where the entire car is rebuild and updated with modern components being a silhouette of stock. Both paths are high buck projects. In the middle is the restorer who is going back to stock but is willing to take advantage of current technology resulting in improved safety, economy and reliability. Typically these enhancements are non-destructive and can be back to stock. An example of this approach is you wouldn?t use 1940?s vintage oil products in a rebuild flathead when you have a e a modern synthetic oil to protect your engine investment. Suggestions in this section follow this approach with the objective of getting more flatheads safely on the road.
Optima Battery
Many of the electrical problems can be traced back to having too small a battery or battery cables. Group 2 six volt batteries are generally not available from suppliers and require a special order. In addition, wet acid cell batteries are not the best solution for cars driven on occasional basis. A solution dry cell Optima batteries. Using absorbed glass mat (AGM) technology they deliver 650 amps of cranking power. The only problem with the Optima is the physical case which is substantially smaller than a Group 1 or 2 wet cell. Stock battery hold down don't work and the battery looks strange compared to stock. Quail Services provides a Group 2 tar top case designed to mount Optima battery inside.! Now you can have a low maintenance 650 amp battery hidden inside a stock looking case that works with you stock battery tray and hold down.
Battery Cables
Somewhere along the way your battery cables have probably been replaced with 12 volt cables. This results in poor starting especially in cold weather. Replace those 12 volt cables with at lease 0 gauge wire. 00 gauge is even better. Check the links page for electrical parts supplies to find a source to order a correct set. Another source is a welding supply shop as they will have 00 gauge for welding leads.
6/12 Volt Battery With Relay
Another battery option is the split 12 volt wet cell. Currently being sold by Antique Auto Battery and other battery suppliers the idea is very simple. A relay is placed between two 6 volt cells that make up a standard 12 battery. Normally wired in parallel they provide 6 volts. When you use the starter a relay closes and the two cells are now in series providing 12 volts to the starter. This makes for easy starting even in cold weather. The relay has continuous taps for 6 volts so you don?t need to change any bulbs or accessories. Cosmetically they are just ugly. However I had one in my P15 for years when I lived in the Midwest and it work as advertised. If you are going to a show you could always carry a spare 6 volt battery and switch it out for judging.
Steel Belted Radial Tires
In the last 50 years tire technology has seen as many technology advances as the lubrication marketplace. Compared to what was available in 1946 tires are modern marvels. If you are building a daily driver radial tires are the way to go. Several companies including Corker Tire still providing bias ply cord tires for collectors going the stock route. For a daily driver on the freeway at 65 MPH I will take radials. Radials ride smother and quieter, handle better and stop quicker. No annoying flat spot to run out if you park the car for a week. The "safety rim" that was stock on these cars and light trucks are compatible with today's radial tires if they are in good serviceable condition. You don't need to replace your rims or use a radial tube. Biggest issues is the stock valve stem is oval shaped while more modern ones are round and your tire shop may not have oval ones in stock.
The chart below provides information as to what size radial tires you should consider. Corker representatives are very helpful providing information about your choices and once you know what you want you can shop around. Always check tire diameter and make sure it is close to the original stock diameter. Be careful about going too wide. Without power steering even a P215 will be difficult to turn in a parking maneuver. Variations of 5% in diameter size should not impact speedometer reading any noticeable amount. Lastly both Plymouth and Dodge make changes to the specified tire size during the production run. Both went from 16 inch to 15 inch tires. However the factory parts book indicates the same speedometer pinion gear was used before and after the change. This means while the tire profile changed overall diameter was nearly the same between the 15 inch and 16 inch tires.
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16 X 6.00 or 15 X 6.70 |
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BF Goodrich P215/70R15 or Corker 205/75R15 |
27.11 Inches |
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16 X 6.00 |
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16 X 6.50 |
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16 X 6.00 or 15 X 7.10 |
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BF Goodrich P225/70R15 or Corker 215/75R15 |
27.6 Inches |
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3.73 | 16 X 6.00 or 15 X 7.10 |
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16 X6.00 or 15 X 7.10 |
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Silicone Brake Fluid
If you have a P15 or D24 you have had brake problems. Leaking wheel cylinders are most common but master cylinders can fail with little warning. Silicone fluid is the easiest way to improve the reliability of your brake system. I have been using it in my P15 for over 15 years without a single failure. Just a couple guidelines for switching: replace all rubber parts including flex hoses when you switch. This will minimize any contamination problems. Completely flush all steel lines. If they are rusty on the outside this is a good time to replace them. With only a single reservoir master cylinder you want to improve system reliability however possible. Silicone brake fluid does this and don?t forget to keep your parking brake properly adjusted, just in case?.
Distributor Upgrades
Tired of replacing and adjusting points? Distributor bushings worn and points won?t stay adjusted? Distributor upgrade options depend it you still have the stock 6 volt positive ground electrical system or have switched to a 12 volt negative ground system. Because these upgrades provide more accurate spark timing your vehicle will start easier and run better. They are an easy Saturday afternoon project but make sure your mechanical and vacuum advances are working as their correct operation is needed to get best vehicle performance.
For 6 volt owners the best available choice is the PerTronix Ignitor kit. Works with both IGS and IAP Autolite series distributors and is totally installed inside the stock ignition. An external control box is not used. For 1935 to 1950 model years use part number 2563LSP6. The P6 is the required code for 6 volt positive ground electrical system. The 2563LS part number is for 12 volt negative ground systems. For more info go to PerTronix.com and download the PerTronix Ignition Catalog.
A second option is a Crane Cams optical ignition system if you can find one. Early in 2002 Crane stopped offering the 6 volt positive ground version of this kit but they do show up on eBay occasionally. The 6 volt positive ground kit is model number is 700-6231. It too works with your stock ignition and doesn?t require any modifications which can not be reversed. The kit consists of a plastic shutter which sits under the rotor. After unscrewing the points, capacitor and lead wires, a "C" shaped bracket is mounted on the distributor plate. It contains a light emitter and collector, which functionally replaces the mechanical points. A controller is mounted on the firewall or hidden under the dash. After adjusting, you will never have to set your points or timing again. I have run these units in my P15 and B1 truck and have had zero problems over the years. For those running 12 volt negative ground systems a 12 volt kit is available from Crane Cams. Check their web site for current model numbers.
A third option is modifying a mopar slant six distributor and using it's entire ignition system. This is only for owners running 12 volt negative ground systems and is a more challenging modification. You will need to shorten the distributor shaft on the on the slant six and reweld together, plus work any issues such as how it is mounted and attached. Their are several threads on the forum from owners who have done this modification so it is the best source for both background info and advice.
FM/iPod Radio Conversion
One of the common reasons given for converting the 6 volt system to 12 volt is to be able to install a FM radio/iPod sound system. Instead of rewiring the car you can now add this functionality your existing Mopar radio. Hemmings Motor News list several suppliers who perform the conversions. I had one of my radios converted by Bob's Radio TV Service, Pismo Beach, CA (bobsradio.com). The unit looks 100% percent stock. When you turn it on the AM works normally, including the pushbutton presets. Turn the unit off and on and it receives FM. Options include stereo and high power amps.
Quartz Clock Conversion
One nice accessory, especially on the D24, is the electric clock. Only problem is the one you have probably doesn?t keep correct time. A common solution is update the clock mechanism to a modern quartz movement. Hemming Motor News lists numerous suppliers for this service. I had my P15 clock updated by Instrument Services (clocksandgauges.com) over twenty years ago and still keeps perfect time. They also offer a do-it-yourself conversion kit for wannabe watchmakers.
Air Shocks
If your rear leaf springs are tired and sagging a less expensive option to replacing them is add a set of adjustable air shocks. You can adjust the body height back to stock and they help reduce body sway around the corners. If you take a road trip and load up the trunk they work great for leveling the load and keeping you headlights pointed in the right direction ! Installation is straight forward and you can easily conceal the small air filler hoses. I have had a set of NAPA branded shocks on my P15 for years without any problems. It is likely I will continue to use them after I replace the leaf spring just for the firmer handling ride.
Flathead 6 Performance Enhancements
Want more horsepower and torque without the headache of an engine swap and conversion? Hotter cams, dual carb intakes and headers are now available from many suppliers. Just check the Links page for contact info. Engine dress accessories like polished finned valve covers and air cleaners are also available.