Originally developed in 1959 for the Ford Anglia, it is an in-line four-cylinder overhead valve (OHV) pushrod engine with a cast-iron cylinder head and block.

The original OHV three main-bearing Kent engine appeared in the 1959 Anglia with a capacity of 1.0 L (996.7 cc) developing 39 bhp (29 kW) at 5,000 rpm — unusually high for the time.

In addition to its 'over-square' cylinder dimensions, a further unusual feature of the Kent engine at its introduction was an externally mounted combined oil filter/pump unit designed to facilitate low-cost production and easy maintenance.

Applications: A 1967 redesign gave it a cross-flow type cylinder head, hence the Kent's alternative name Ford Crossflow.

The 1.6 L (1,599 cc) 691M block had the stronger 'square' bearing caps later used in the 711M, and small combustion chambers in the near-flat head (the bulk of the volume being in the piston bowl).

Destined for the American market, beginning with the 1977 model year, the Valencia plant began manufacturing a 1.6L, 63 bhp (47 kW), five-main bearing version that included a low emission bowl-in-pistons combustion chamber design based on the Crossflow head, and was equipped with a Dura-Spark electronic ignition.

Fitting the Crossflow into the Mk1 Fiesta posed a challenge for engineers, since the car had been designed around the shorter Valencia version (below), therefore the engine had to be mounted lower down in the chassis with shorter driveshafts in order to allow the transaxle to be removed from the car for clutch replacement.

This engine was later used in the XR2 version of the Mk.1 Fiesta, using the US 1600 bottom end and GT spec head and cam but without the catalytic converter or emission control equipment.

This derivative went through two major revisions in 1988 and 1995, detailed below, and was a mainstay of Ford's entry level compact range for nearly 25 years.

To adapt the Kent Crossflow for front wheel drive the ancillaries were repositioned, and the cylinder block shortened by 30 mm (1.2 in).

The bore diameter was reduced to 74mm (from 81mm on the full-size Kent), and was standard across both the 957 and 1117 versions; the extra capacity was achieved by varying the stroke.

The cylinder heads and pistons were modified in 1986 for unleaded fuel and the cams changed to meet the new European emissions standards along with the addition of electronic ignition.

[2] The substantial redesign of the engine included an all-new cylinder head with reshaped combustion chambers and inlet ports for 'lean-burn' operation, hardened valve seats and valves for operation on unleaded fuel, and the Ford EDIS fully electronic ignition system, with the option of single-point fuel injection for use with a catalytic converter - Weber carburettors were specified to replace the unreliable Ford Variable Venturi (VV) unit.

The HCS engine is easily distinguishable from the original Valencia by the rocker cover, head and block being painted grey instead of black, the presence of a crankshaft position sensor adjacent to the starter motor, and the absence of a distributor drive on the rear face of the cylinder block.

This edition was effectively another redesign of the Valencia/HCS derivative, known as the Endura-E, and featured many revisions to combat noise and harshness, including a thickened cylinder block and a cast aluminium sump.

This mounting position makes it very difficult to access from underneath the car (without a mechanic's ramp), and despite being very short, the can-type oil filter still manages to protrude past the tip of the adjacent starter motor, meaning it is very difficult to remove using chain-type grips.