The small-block Ford’s ignition, charging, and starting systems evolved considerably between 1962 and 2001. The greatest engineering achievements in these areas were Duraspark electronic ignition and the solid-state charging systems in the 1970s and 1980s. These high-tech wonders can be adapted to vintage Ford electrical systems. Later, starters evolved from conventional direct-drive units to reduction-gear high-torque starters.
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Ford designed its ignition systems to be simple from the start. In the small-block Ford’s early years, the Autolite ignitions were consistent and reliable with only minor changes and excellent interchangeability. Ford offered a single-point Autolite distributor with vacuum advance and a dual-point Autolite distributor devoid of a vacuum advance unit, the latter for the 289 High Performance V-8 introduced in 1963. Ford Autolite ignition systems of the period receive their power from a pink resistance wire from the ignition switch to fire the ignition coil. Full 12- to 14-volt ignition power comes via the starter solenoid during start mode only.
Vintage Autolite/Motorcraft distributors are notorious because they consist of a shaft supported by one lone bushing, sometimes two in later years and applications. These bushings wore out quickly causing unacceptable shaft oscillation, point bounce, and dwell irregularity resulting in poor performance. Unless you have a good relationship with a bearing company and a machine shop, there’s little you can do with the Autolite/Motorcraft distributor except install new oil-impregnated bushings (both the long and short bushings for optimum performance). Both the shaft and bushings must be measured with clearances checked.
Autolite distributors prior to the 1970s were fitted with vacuum- advance units you can tune by adding shims to slow the rate of advance and removing them to speed up the rate of advance. Centrifugal fly-weights beneath the breaker plate work against spring pressure to control mechanical advance as engine RPM increases. It really is a very simple system that’s easy to tune.
Beginning in 1968, Ford used a dual-advance/retard vacuum unit on vehicles equipped with Improved Combustion (IMCO).
The unit operated by two vacuum lines, one for advance and one for retard. The IMCO system was designed to reduce hydrocarbon emissions and was a means to more precise spark control. The dual-advance/retard system advances spark timing during acceleration and retards spark timing during deceleration when hydro-carbon emissions increase. Because IMCO incorporates a distributor vacuum-control valve at the ther-mostat housing (except Cleveland, where it is in the block), spark timing is advanced whenever the engine becomes too hot at idle. This increases engine idle speed to both improve coolant flow and reduce emissions.
IMCO was more than just spark control. It also had revised combustion chambers and leaner fuel mixtures, which adversely affected performance.
Single- and Dual-Point Systems
Single-point distributors differed only in spark curve, depending on vehicle application. Prior to 1965, Autolite distributors had an oiling wick designed to be serviced with SAE 30-weight engine oil at tune-up time every 12,000 miles. In 1965, the oil wick was eliminated in favor of an improved spiraled shaft that carried oil up to one lone bushing.
The problem was, and still is, these distributors suffer from inad-equate bushing and shaft support. Because bushings and shafts are typically oil starved, they wear quickly, causing excessive play and point bounce. Oil-impregnated replacement bushings help, but don’t really solve the problem.
With the Boss 302 in 1969–1970 came a dual-point ignition system with vacuum advance/retard to meet tougher emission standards. Vacuum advance/retard was another effort at reducing emissions on all Fords at the time.
Vacuum Advance System
Original vacuum advance units can be dialed in via shims and a spring, as mentioned previously. Aftermarket replacement vacuum advance units are adjusted via the vacuum port with an Allen wrench. Adjust clockwise (tighten) to slow the rate of advance; adjust counterclock-wise to increase the rate of advance.
The advance system also includes mechanical or centrifugal advance, which advances timing as engine RPM increases. A simple way to look at spark advance is what each type of advance does. Vacuum advance gets you started and helps maintain power with a light foot on the accelerator. Centrifugal advance takes over as the engine roars into higher RPM. Total spark advance should be completely in by 3,500 rpm and you should have 34 to 36 degrees before TDC by 3,500 rpm. Absolutely no more than 36 degrees or you risk serious engine damage.
The 289 High Performance distributor is not fitted with any kind of vacuum advance. A centrifugal mechanism advances spark as RPM increases. Because the high-revving 289 Hi-Po does its best work at high RPM, total timing is completely in by 5,000 rpm, with peak horsepower and torque at 6,000 rpm. Spark timing on the 289 Hi-Po should be 12 degrees before TDC at idle. Again, keep total timing below 36 degrees before TDC.
Ford introduced Duraspark electronic ignition in 1973 in its continuing quest to improve emissions and reliability. Duraspark II followed in 1977, with Duraspark III following in the 1980s with electronic engine control (EEC). Duraspark III was used in conjunction with EEC-III and EEC-IV systems. Most of the differences are in the Duraspark ignition module as improvements happened elsewhere in the system.
The Duraspark ignition module does exactly what points do: switch the ignition coil off and on, triggered by the distributor, for good coil saturation and a hotter spark. If you’re performing a simple retrofit, you want Duraspark II for a small-block Ford.
The best place to mount a Duras-park module is on the firewall behind the engine. All you need is a Duras-park distributor, ignition module, coil, and wiring harness. If you don’t have the harness, Painless Wiring can help with a retrofit system that makes it easy to convert from points to electronic ignition.
Duraspark and Duraspark II distributors have a conventional vacuum-advance unit. There is no retard feature. In the mid-1980s, with the advent of EEC, Ford switched to a thick-film ignition module distributor, which advances the spark via a signal from the EEC-IV module.
In 1980–2001 small-block Ford part numbers became more complex due to tougher federal emissions standards. Dozens of distributor applications are available for the 4.2L (255-ci), 5.0L (302-ci), and 5.8L (351-ci) engines based on individual vehicle applications. Each Motor-craft distributor was factory calibrated and assigned a specific Ford part number and Motorcraft replacement part number based on where it would be installed (California, 49-state, high altitude) and vehicle composition.
Unless you’re performing a concours restoration on a 1980–2001 Ford, Mercury, or Lincoln, these part numbers are less important to you than fitment and tuning. This is the reason that I do not list their identification details in this book.
Fitment and Calibration
In your search for the appropriate distributor for your late-model small-block Ford, you should be most concerned with fitment and spark advance calibration. The Duraspark and Duraspark II distributors are Hall effect magnetic trigger ignition systems with mechanical and vacuum advance.
If you have a Duraspark or Dura- spark II distributor, your main concern should be mechanical and vacuum advance calibration, which you can do yourself. Duraspark is simple, old-fashioned spark timing with the reliability of electronic ignition.
Engines with CFI and SEFI were fitted with electronic spark control (EEC-IV), which includes the Thick Film Ignition (TFI) distributor. Known as Duraspark III, with help from Ford’s high-tech EEC-III or EEC-IV electronic engine control, the TFI distributor employs electronic spark control technology in its thick-film module.
Ford had problems with TFI due to engine heat and ignition shutdown. Ford has since solved this problem with improved Motorcraft replacement thick-film modules. The after-market (MSD and Ford Performance) also offers improved-performance thick-film modules.
When Ford revisited thick-film technology in the early 1990s, it moved the TFI module away from the distributor to a cooler location in the engine compartment. This means that you can expect to see two types of TFI distributors, internal and external. Keep this in mind when you’re amassing parts for your small-block project.
In the late 1990s, Explorers with 5.0L High Output engines went to a Distributorless Ignition System (DIS) where the Motorcraft TFI thick-film Duraspark distributor was eliminated entirely.
Generators and Alternators
Between 1962 and 1964, all small-block Fords were factory fitted with a 30-amp generator charging system with an external voltage regulator. All generators were virtually the same; the only real differences are pulley size and number of sheaves (grooves). Standard applications received the 2.67-inch-drive pulley with one or two sheaves. The 289 High Performance V-8 was fitted with a 30-amp generator with a one-sheave 4.32-inch pulley.
The Autolite/Motorcraft 1G alternator was Ford’s mainstream alternator from 1965 until 1982 when the higher-amp internally regulated Motorcraft 2G took its place. If you’re in the market for a 1G be advised that there were changes in cases and differences in amperage. You find the rounded-case 1G units with and without the “Autolite” name. Beginning in 1972, you find rounded 1G cases with and without the Motorcraft name. Square-case Motorcraft 1G alternators arrived in 1972–1973.
Beginning in 1972, Ford redesigned the 1G with a square case and the Motorcraft name when the Auto-lite brand was sold to Bendix. Despite the name and case changes, the 1G’s internals did not change and can be swapped into any case combination. You can buy a remanufactured 1G alternator and swap its components into your preferred case if authenticity is important.
The internally regulated Motor-craft 2G alternator first arrived on full-size Fords and Mercurys in 1982. In due course, the 2G alternator wound up in other Ford car lines, including Mustang and Capri from 1986 to 1993.
The Motorcraft 2G alternator was produced in 65- and 75-amp sizes, which made it marginal for Fords with electronic engine control and a lot of accessories. It is nicknamed the “fire starter” due to its three-pin plug, moisture, and corrosion issues at the plug that could start a fire. High resistance and short-circuits made the 2G a fire hazard, which is why enthusiasts have converted their applications to the 3G alternator. The 2G looks similar to the older 1G, yet the two alternators are quite different.
Smallblock Fords have always been fitted with two-bolt starters. Over the entire history of the small-block Ford, three basic starter types were used. Selection depends on your application, which includes transmission type, bellhousing type, and flywheel/flexplate size.
From 1962 until the 1980s, Ford used the same basic direct-drive Autolite/Motorcraft starter. As the 1980s unfolded, Ford changed to a smaller, more compact size Motorcraft directdrive starter, which can be easily identified when you place it alongside an older Autolite/Motorcraft starter.
Beginning in 1992, Ford used a lighter Permanent Magnet Gear Reduction (PMGR) starter on small-block Fords, which was a dramatic change from previous starters. It also meant losing 12 pounds in starter weight; the older Ford starter weighs 20 pounds and the PMGR weighs 8 pounds.
The PMGR starter has all of the same issues as the vintage Ford starters in terms of fitment and application. One size does not fit all. There are variations between 157-tooth versus 164-tooth and manual transmission versus automatic transmission. Be sure you have all this nailed down before you order a starter.
If you have a manual transmission, the correct PMGR starter has a recessed starter drive gear. In contrast, the automatic PMGR starter drive sticks out 3/8 inch to reach the flexplate ring gear. You have to determine whether you have a 157-tooth or 164-tooth flywheel or flexplate. If you have an AOD or AODE (4R70W) transmission, you have a 164-tooth flexplate. If you have a T-5 5-speed manual transmission, you have the smaller 157-tooth flywheel.
Senders are included in this chapter because they are also part of your small-block’s electrical system. They keep your engine’s vital gauges working. Senders are either on/off switches or variable resistors to ground. Very low voltage (1.5 volts) flows through the instruments to the senders to ground. Senders determine how much current flows to ground, which determines gauge indication.
Variable-resistance senders vary resistance to ground. When there is high resistance to ground, the gauge reads low because there’s low current flow to ground. For example, the oil pressure or coolant temperature gauges read low when there is high resistance to ground. When oil pressure or coolant temperature is high, there is greater current flow to ground, which causes the gauge to read higher.
Senders for warning lights are a simple on/off affair. If you have low oil pressure, as one example, the sender closes to complete the circuit to ground and the light comes on. When you have sufficient oil pressure, the sender opens the circuit and the light goes out.
Written by George Reid and Posted with Permission of CarTechBooks
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