Small Six Identification

Ever wonder what size motor you have? If so, your not the only one. To the inexperienced enthusiast all small sixes look identical, however there are minor differences which can be easily spotted if you know what to look for. In this article we’ll cover a majority of the differences, for engines produced in the USA, even though you only need to know three to identify the engine size

While Australian and/or Argentina built motors are similar to their US counterparts, they have their own unique set of differences. Some of these differences are the same as their US counterparts, while many are not. For example, all US-250ci engines had a low mount starter, while the Australian and Argentina 250’s had a high mount starter. Therefore exhaust headers produced for an Australian 250ci will not fit the US-250ci, or vice versa. Another example would be the oil pump, while the oil pump drive is the same size, the bolt patterns are different. Therefore the oil pumps are not interchangeable. The US-200/250ci distributors and cylinder heads will fit an Australian 200/221/250ci Pre-Crossflow, and vice versa. However the AU-250ci Crossflow distributors and cylinder heads are unique to the Crossflow and will not interchange with the US-200/250ci engines. One last example is the oil pan, also non-interchangeable, as the Australian and Argentina 250ci oil pans (and blocks) are one inch narrower in width. The list goes on…..

General Description: The Small Six (or Falcon Six), overhead valve, inline 6-cylinder engine was introduced in 1960 with a cast iron block and cylinder head. All US cylinder heads incorporated an integral one barrel intake manifold, more commonly known as a log intake. The crankshaft and flywheel are dynamically balanced, and the crankshafts are fitted with a harmonic damper, which is often called a balancer.

Left side 170/200

Block Codes: Block codes were an attempt at a cast-on block identification system & can be found on the road draft tube mounting boss. Block codes were in use up to 1964, or there about, then Ford switched to small metal tags that were bolted to the engine block.

The block codes were as follows 144ci: “N”, 170ci: “T” Note: 200/250ci engines, and some 170’s, did not have block codes, as metal tags were used instead.


Below is an example of the tags used on engines from 64 on. This is the tag from a 1969 250ci engine. They are quite similar to those found on carbs, rear ends and transmissions. They are usually quite accurate, and were normally installed on one of the coil bracket bolts. Unfortunately they are commonly lost or left off after a rebuild.


  • 250 is the displacement of the engine.
  • 69 is the model year of the engine.
  • 1 is the change level.
  • 8-L is the year & month produced (68-Dec).
  • K45-S is the engine code number.


The engine code number & change level were intended to assist engine shops when they ordered parts. In actual practice very few paid any attention to these numbers, as they only served to complicate the ordering process. Therefore we will not discuss them in greater detail.

Four Main
Four Main


Seven Main
Seven Main


Main Bearings: All 144/170ci, and 200ci blocks prior to mid ’64, had four main bearings. While the 200ci from mid ’64 onwards, and all 250ci blocks, had seven mains bearings.

Rods: All 144/170/200/250ci engines have forged H section connection rods, with the exception those built in 78-79, which used either cast iron, cast steel, or nodular iron.

Stroke: The 144ci engine has a 2.50 inch stroke, while the 170ci has a 2.94 inch stroke. The 200 has a 3.13 inch stroke, while the 250ci engine has a 3.91 inch stroke.

Pistons: All 144/170ci engines have cast aluminum flat top pistons with a 3.50″ diameter, while the 200/250ci engines utilized a dished piston with a 3.68″ diameter. The dish size was normally 6.5 cc’s, however a 13 cc dish was used in California engines, which lowered the compression ratio and reduced emissions.

Cylinder Bore: All 144/170ci engines have a 3.50 inch cylinder bore, while the 200/250ci have 3.68 inch cylinder bore.

Cylinder Heads: Depending on the production year, the chamber size, valve size, intake size (manifold volume), and carburetion varied considerably. Carb bores were as follows: 144/170ci: 1.325″, early 200ci: 1.500″, later 200/250ci: 1.75″ (all were 1V carbs).

Lifters: ’60-’62 144/170ci engines had solid lifters, ’63-’65 144/170ci engines had both styles depending on the year and model, while ’66-UP 144/170ci engines had hydraulic lifters. All 200/250ci engines had hydraulic lifters. Example: The ’64 Falcon 170ci had hydraulic lifters, while the ’64 Ranchero 170ci had solid lifters.

Rockers: ’60-’62 144/170ci engines had adjustable rockers, ’63-’65 144/170ci engines had both adjustable and non-adjustable rockers, depending on the year and model, while the ’66-UP 144/170ci engines had non-adjustable rockers. All 200/250ci engines had non-adjustable rockers. Example: a ’64 Falcon 170ci with hydraulic lifters had non-adjustable, while the ’64 Ranchero 170ci with solid lifters had adjustable.

Distributors: All 144ci engines, and 1960-mid’64 170ci engines, had a 1/4″ hex drive-shaft. The mid’64-UP 170ci engines, as well as all 200/250ci engine,s had a 5/16″ hex drive-shaft. Note: This is only a rule of thumb, as it may vary depending on the year and model type.

Starters: Most 144/170/200ci engines had high mount starters, which were mounted above the oil pan rim, while the 250ci engines had low mount starters, which were mounted below the oil pan rim. However some 200ci engines, used in Econoline vans and trucks (1980-83), had custom bell housings (similar to a SBF bell) which utilized a low mount starter.

Freeze Plugs: The 144/170ci engines have 3 water jacket freeze plugs which are visible directly below the exhaust manifold, while the 200/250ci engine have 5 freeze plugs.
This is the easiest way to distinguish the 144/170ci from the 200/250ci engines.

Water Pumps: All 144/170/200ci engines used a 3 bolt water pump, while the 250ci six utilized a 4 bolt water pump. This is the easiest way to distinguish a 250ci from the 144/170/200ci six.

Color Schemes: The 144ci has a blue valve cover and air cleaner, and black block. The 170/200ci engines had an orange valve cover and air cleaner, and a black block prior to 1965. From 1965 onwards the 170/200ci engines had a Ford blue valve cover, air cleaner, and block. Some early 170/200ci motors had an orange oil pan as well. The 250ci engine came with a Ford blue valve cover, air cleaner, and block. However, these color combos were not set in stone, as they did change on some models, and/or specials. Hence this is only a general guideline.

Summary: Here’s how to figure out what size the block is. Identification can be made with a quick glance at three items on the motor, the water pump, number of freeze plugs, and the block code (found on the road draft tube mounting boss). The only trick is determining the difference between a 170ci 4 main and a 200ci 4 main, if there is no block code, as both engines had a three bolt water pump and three freeze plugs. The only way I know of for sure, is to verify the bore size. If I learn of another method, I’ll let you know.

  • 250ci -7 main: 4 bolt water pump and 5 freeze plugs.
  • 200ci -7 main: 3 bolt water pump and 5 freeze plugs.
  • 200ci -4 main: 3 bolt water pump and 3 freeze plugs.
  • 170ci -4 main: 3 bolt water pump, 3 freeze plugs, and a “T” code (or no code).
  • 144ci -4 main: 3 bolt water pump, 3 freeze plugs, and an “N” code.

(Note: Early 144/170’s had a 1/4″ distributor drive, later 170’s had a 5/16″ drive).

Written by: AzCoupe