The OHC engine
OHC ("Pinto") Engine : Very much the 'old faithful' of the Sierra range throughout the years. First introduced to the UK in 1970 in the Mk. 3 Cortina, the Pinto engine was the OHC engine for the masses with it's cheap rubber-belt-driven design.
Over the years it has served millions in the UK alone - be it in Escort RS2000's, Cortina's, Sierra's, Granada's or the everyday Ford Transit van.
Initially available in 1.3, 1.6, 1.8 and 2.0 capacities, the Pinto was gradually phased out. Unable to meet the strict new emissions guidlines coming into force over the 1990's, Ford decided the humble Pinto had had enough and replaced it. The 1.3 went first - it wasn't really suited to a car the Sierra's size anyway - followed by the 1.8 in 1986 (replaced with a CVH unit); then the 2.0 with a new engine altogether in 1989 (the 2.0 8-valve DOHC). The 1.6 finally disappeared at the end of 1991 with the introduction of the 1.6 CVH with central-point fuel injection (CFi) though it has been known to find the occasional 1.6 Pinto in base-model cars as late as the '93-model year - cars that were built right at the end of the production run were rumoured to be "parts bin specials" and this seems bourne out by the aged interloper where a central-point-injected CVH should have ruled.
The OHC engine is easily and readily tunable thanks to its involvement with motorsport in the 1970's. While the engine is noted for its reliability and practically bulletproof constitution - they have been known to run with little oil or go on for miles with blown headgaskets - they are harsh compared to the 2.0 DOHC engine that replaced it, and a standard 2.0 DOHC engine often produces better power and torque compared to a mildly-modified OHC.
Technical Overview :
The engine is an 8-valve unit and was available only with a carburettor up until 1984 when Ford paired the engine with a Bosch L-Jetronic Electronic Fuel Injection system. EFi versions were rated at 115bhp and were initially found in the 2.0 iS special edition. Later on it was standard on GLS and Ghia models.
Comprised of a cast-iron engine block with a cast-iron cylinder head and pressed steel oil sump. The crankshaft is supported in five main bearings and drives the camshaft through a toothed rubber timing belt. An auxialliary "idler" shaft powering the fuel and oil pump and the distributor is also driven by the timing belt. The timing belt on earlier models is tensioned by a spring-laden jockey wheel. Later models retain the jockey wheel for tensioning, but it is no longer spring loaded and must be manually adjusted to give the correct belt tension.
Cylinder heads on EFi models and all engines from 1990 onwards are able to run continuously on unleaded petrol without further adjustment. EFi cylinder heads also feature a slightly revised inlet tract design that lends itself to higher flow rates compared to cylinder heads intended for carburettor use.
Cylinder blocks bearing a cast-in "205" mark - found in injection models - are stronger than those used in other 2.0 models and lend themselves to overboring.
The OHC engine was used as the basis for the 16-valve YB engine found in Cosworth models - though many components are different (such as steel crank in the Cosworth engine), from the cylinder head gasket downwards the engines look visually identical.
OHC engine with Electronic Fuel Injection (EFi):
OHC engine with Carburettor:
What goes wrong? :
Timing Belts can break in use if the service interval has been ignored, or the belt has become contaminated with oil. This can cause extensive engine damage on 1.8 and 2.0 engines. The Ford service interval for the timing belt is 36,000-miles but practical experience has shown it best to ignore that and change it every 20 - 25,000 miles or two years as it is a simple operation. It is recommended to check the condition of the belt every service as a matter of course, even if not replacing it.
Camshafts and tappets wear rapidly thanks to flaws in the design of the oil lubrication system. The camshaft and valve gear is kept supplied with oil through a small-bore steel pipe, drilled with holes at appropriate intervals to ensure oil sprays onto the camshaft lobes. Even if the service interval is honoured, this pipe can sludge up and block, starving the valve gear of oil - causing wear to set in at an increased rate. Cam bearings can also suffer - but replacement is straighforward.
When worn beyond adjustment, the only solution is to replace the camshaft and followers as a complete kit - which involves removing the cylinder head as the camshaft withdraws out of the rear of the head - but kits are readily available and relatively cheap.
Carburettors can be problematic - especially earlier 1.6 models fitted with Ford's curious Variable Venturi (VV) unit. Later 1.6's and all 2.0's were fitted with much better Weber twin-choke units of various designations (early cars had DGAV units, later ones DMTL (?)), all of which could suffer with automatic choke problems.