Small-block Ford ignition systems are simple to understand and service. Ford designed them that way from the start. In the early years, they were consistent and predictable with only minor changes and good interchangeability. There was a single- point Autolite distributor with vacuum advance and a dual-point Autolite distributor with no vacuum advance unit, the latter being for high-performance applications. With Boss 302 in 1969–1970 came a dual-point ignition with vacuum advance/retard. Vacuum advance/retard was another effort at reducing emissions on all Fords at the time. It wasn’t unique to just Boss 302.
This Tech Tip is From the Full Book, HIGH-PERFORMANCE FORD ENGINE PARTS INTERCHANGE. For a comprehensive guide on this entire subject you can visit this link:
SHARE THIS ARTICLE: Please feel free to share this post on Facebook / Twitter / Google+ or any automotive Forums or blogs you read. You can use the social sharing buttons to the left, or copy and paste the website link: http://www.diyford.com/ford-small-block-ignition-starting-charging-interchange/
Single-point distributors differed only in spark curve from 1962–1967 depending on vehicle application and destination. Prior to 1964–1965, Autolite distributors had an oiling wick designed to be serviced with SAE 30-weight engine oil at tune-up time every 10,000 miles. In 1965, the oil wick was eliminated with an improved shaft that carried oil up to one lone bushing. The problem was (and still is) these distributors suffered from inadequate bushing and shaft support. Because bushings and shafts are oil starved, they wear quickly, causing excessive play and point bounce. Oil-impregnated replacement bushings help, but don’t really solve the problem. Original equipment vacuum advance units can be dialed in via a system of shims and a spring, which controls the rate of timing advance. Add shims to slow the rate of advance, or reduce the number of shims to increase advance rate.
Vacuum advance/retard (also known as dual-advance) was an integral part of the IMCO (Improved Combustion) emission control system launched in 1968. IMCO works on a principle of applying manifold vacuum to both sides of the advance/retard unit depending upon vehicle operation at the time. Under acceleration, you advance the spark. On deceleration, you retard the spark to reduce hydrocarbon emissions (unburned fuel). The IMCO system is controlled by a thermal vacuum switch located at the thermostat housing. As coolant temperature warms, the vacuum switch vectors vacuum appropriately to control emissions.
The advance system also includes mechanical or centrifugal advance, which happens as engine RPM increases. A simple way to look at spark advance is what each type does. Vacuum advance gets us started and helps us 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 this is how professional tuners dial in total spark timing: there should be a total of 34 to 38 degrees before top dead center (BTDC) by 3,500 rpm. Absolutely no more than 38 degrees or you risk serious engine damage.
The 289 High Performance distributor is not fitted with a vacuum advance of any kind. Spark advance comes via a centrifugal-advance mechanism that 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 should be 12 degrees BTDC at idle. Again, keep total timing below 38 degrees BTDC.
Although most Autolite/Motorcraft distributors had just one bushing from the factory, B8HQ-12120-A (the long one), you may also fit a smaller bushing, C5AZ-12132-A (the short one), in the housing end for improved shaft support.
In the mid 1970s, Ford went to an electronic ignition system called Duraspark in its continuing quest to both clean up emissions and improve reliability. Duraspark continually got better with time, with Duraspark II and III to follow in the late 1970s and into the 1980s. Duraspark III was used on 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; it switches the ignition coil off and on, triggered by the distributor. If you’re doing a simple retrofit, you want Duraspark I or II for a small-block Ford. All you need is a Duraspark distributor, ignition module, coil, and the 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 distributors have a conventional vacuum-advance unit. There is no retard feature.
In the 1980s, with the advent of electronic engine control, Ford went to a thick-film ignition module distributor, which advances the spark via a signal from the EEC-IV module.
In the late 1990s, Explorers with 5.0L High Output engines went to a DIS (Distributorless Ignition System) where the Motorcraft thick-film Duraspark distributor was eliminated entirely.
From 1962–1964, the Ford smallblocks were equipped with generators. Application depended upon vehicle type and options. See the nearby chart for specific generator and alternator applications. Motorcraft part numbers are shown in parenthesis as applicable.
Autolite/Motorcraft alternator application boils down to the proper combination of amperage and pulley configuration. First, it is important to understand original-equipment alternator types and what they were replaced with. There are seven basic alternator types. The only real sub-differences are pulley sizes and types.
Several fans were used on these alternators. The D0AZ-10A310-A (GP-473A) 10-blade fan is the most common, used on 38-, 42-, 45-, and 55-amp alternators from November 1969 on. The older C5AZ-10A310-B 13-blade fan was used from 1964 until October 1969. Two other fans were used for the largest 65- and 70-amp alternators: the D0AZ-10A310-A (GP-496), used from 1967–1970, and the D2OZ-10A310-A (GP-510), used from 1972 on.
Several pulley types were used on the 38-, 42-, 45-, and 55-amp alternators. Pulley diameter, width, and number of grooves are the most important concerns. Several types were used for smallblock engines. The C5AZ-L (GP-494) piece is a dual-groove pulley with a 2.84- inch diameter and a 1.40-inch total width. The C5AZ-K (GP-493) pulley is 2.84 inches in diameter, like the C5AZ-L (GP-494). However, it is a single-groove pulley with a 1.015-inch width. The D1ZZ-A (GP-465A) pulley is 3.05 inches in diameter and just shy of 1-inch wide, with a single groove.
The 289 High Performance engine through 1967 had the C5AZ-H (GP-580) pulley, which was large (3.90-inches) with a single groove. The large 3.90- inch pulley, is sized to keep alternator speed down at high revs to reduce the risk of winding failure. For 1967 only, the 289 High Performance V-8 had a Hi-Po-specific C7ZZ-A (GP-486) 3.62- inch, two-groove pulley that was 1.49 inches wide. You find this only on the 1967 289 High Performance engine.
There was also the C7TZ-B (GP-485) pulley, a dual-groove, 3.17-inch-diameter piece with a 1.53-inch width. This large piece was common to the large 65- and 70-amp luxury-car alternators. This large-diameter pulley was sized not to keep alternator speed down, but to turn the huge armature more efficiently. Three other large pulleys were used on 65- and 70-amp alternators. The D1AZ-A (GP-508) pulley had a 3.12-inch diameter and .85-inch width in a single-groove design. The D2OZ-A (GP-511) pulley was 3.15 inches in diameter with a .91-inch width in a single-groove design. And finally, there was the D2AZ-A (GP-578) pulley with a 3.15-inch diameter, 1.49- inch width, and dual-groove design.
Starter selection is pretty straightforward for Ford small-blocks. Three basic types were used, depending upon vehicle, engine, transmission, and flywheel/ flexplate type. The end result here is proper flywheel/flexplate engagement. If you use the incorrect starter for your application, you might be greeted with the sound of a spinning starter drive that doesn’t have a prayer of engaging the flywheel/flexplate. Using the right starter is important. To follow is a table of popular Ford starter applications. Use this table to choose the correct starter for your application.
Written by George Reid and Republished with Permission of CarTech Inc
GET A DEAL ON THIS BOOK!
If you liked this article you will LOVE the full book. Click the button below and we will send you an exclusive deal on this book.