The Difference Between Early and Late Models
Most parts are interchangeable between early and late model engines. However, a few parts (particularly some of those used in fuel, ignition, and cooling systems) are unique to early or late models.
If you have an original engine from the mid-seventies or later, with an oil fill tube over the flywheel housing in front of the engine, you can be reasonably sure that your engine will require all late model parts.
If your engine does not have an oil fill tube over the flywheel housing, it may require a mix of late and early model parts. You will therefore need the following information before ordering:
1. To order ignition parts (including the "Ignitor"), you will need to know if your distributor was manufactured by Delco (used on late model engines), or by Prestolite (used on early model engines). Prestolite distributors are distinctively smaller in size, and their condensers are mounted on the outside of the distributor housing.
2. To order cooling system parts, you will need to know if your engine has a thermostat housing (a small dome-shaped casting) located on the front corner of the head, nearest the starter. This thermostat housing would indicate that your engine has a late model cooling system.
3. To order carburetor parts, you will need to know if your carburetor is made of aluminum or cast iron. Aluminum carburetors were used on late model engines. All carburetors were manufactured by Zenith or Bendix, so the manufacturer does not help in determining your carburetor vintage.
4. To order gaskets, you will need to know (1) and (2) above, plus the shape of your transmission cover. Late model engines used a square cover, and early model engines used a rectangular cover with a curved top ("tombstone-shaped").
5. Late model (Delco) starter ring gears have slightly smaller teeth than early model Prestolite ring gears. For this reason, Prestolite and Delco starters cannot be exchanged between early and late model engines unless the ring gear (or entire flywheel) is changed with them.In addition, late model ring gears have a slightly larger diameter than early models, so when moving a late model flywheel to an early model engine, either a late model housing will also have to be moved along with the flywheel or the six (6) small boss areas the inside of an early model flywheel housing will have to be ground down. These boss areas are for the ¼ - 20 bolts that hold the flywheel cover on, and they will have to be ground down almost to the bolt holes themselves.
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