Escort Cosworth Upgrade

We started work some time ago on a project which was intended to bring the very latest technology to a legend of yesteryear,  namely the Ford Escort RS Cosworth.

The Escort Cosworth has been the subject of tuning and upgrades since it was first launched in the early 1990’s, but there has not been any real progress in the development of the car or high performance components for many years.

Being familiar with the very latest technology intended for new cars, we decided to apply the design and manfucturing methodologies that we had learned, so that we could bring something new and exciting to the world of the owners of the Escort Cosworth.

Fortunately, our Workshop Manager owns one of the best examples of Escort Cosworth currently in existance. It is pristine in every respect, and as you would expect from the man in charge of one of the best tuning facility workshops in the UK, he has the determination to produce something very special and create a compleley new benchmark by which other efforts may be judged.

The first subject for our attention was the Cosworth YB engine which was stripped, inspected, modified where appropriate, blue printed then re-assembled.

This is the engine as removed from the car as a complete unit with the transmission.

escort cosworth engine

Here’s a picture of the underside of the car after the engine has been removed.


Here’s the engine prior to disassembly


This car has been used very hard so showed normal signs of wear and tear.  The oil pump gears have clearly passed contaminated oil.

Escort cospwrth oil pump

The main bearings show signs wear too:


The Cosworth crankshaft is manufactured from steel so is very strong. It was crack tested, checked for ovality, taper and wear, then was micro polished:

escort cosworth crankshaft


The standard Cosworth connecting rods are robust enough so they were retained after being crack tested, checked for length and bore conformity, then fitted with new bolts:

cosworth connecting rods

We chose Wossner forged aluminium racing pistons over the brands because of the low recommended clearance and the anti-skuff coating, both of which will bring long term value:

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The Escort Cosworth YB cylinder block is the next component to be processed.

Firstly it is de-greased and receives a chemical wash.

The next process is to assemble a deck plate so that the cylinders can be bored and honed. The theory behind this process is that when the cylinder head is unbolted from the cylinder block, the cylinder block deforms slighty. If the cylinder block is bored and honed in a deformed state, the cylinders will go out of shape when the cylinder head is re-fitted. Boring the cylinders while a deck plate is torqued onto it ensures bore conformity in service. The YB cylinder block is then processed to machine for heavy duty cylinder head studs and head gasket O rings.

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After machining, the following processes are applied: measure cylnder bore size, ovality and taper to ensure that the boring has been carried out correctly, measure and correct piston ring clearances, measure piston to cylinder clearances, measure and correct crankshaft end float, main bearing and connecting rod bearing clearances, measure deck to piston heights, measure and balance combustion volumes.

Crankshaft in position with assembly lube and heavy duty main bearing cap studs:

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Crankshaft, pistons and rods installed:

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Short block fully assembled:

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Cosworth YB Cylinder Head Development:

The standard cylinder head is exceptionally restrictive in terms of air flow volume so it is absolutely essential to increase the air flow by modifying the intake and exhaust ports.

This cylinder head had already been modified by another company so we decided to check the efficiency of the mofifications on our Superflow air flow test bench.

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The results of our testing were not very impressive so we concluded that further modifications were necessary.



The Escort Cosworth cylinder head exhaust ports were significantly enlarged and straightened to yield a substantial 50% increase in air flow compared to the cylinder head. This increase will enhance volumetric efficiency and lower the cumbustion temperatures. This picture shows the raw finish just after hand grinding, the finish is subsequently cleaned and smoothed:



After porting and polishing, the cylinder head is fully assembled with valve springs and adjustable pulleys, then fitted to the short block:

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Final engine assembly with some auxiliary components:

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Escort Cosworth Exhaust Manifold:

In the Escort Cosworth tuning world there seems to be a trend towards replacing the 4WD standard exhaust manifold with the 2WD exhaust manifold, so we evaluated both for air flow efficiency on our Superflow air flow test bench.

The 2 wheel drive Sierra Cosworth manifold is a two piece casting which has a change in direction of almost 180 degrees, so we were not surprised to see that the shorter and straighter Escort Cosworth 4 wheel drive manifold has significantly higher air flow volume.  We did not undertake any calculations to estimate any differences based around exhaust gas harmonics, but we selected the less efficient 2WD manifold because of the packing concerns of our intentions to experiment with a new design of turbocharger at a later date.

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Escort Cosworth Inlet Manifold:

The standard Escort Cosworth inlet manifold is compromised for high power applications, so we installed a specially manufactured high volume plenum to provide better mid-range and high speed power:

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Not only very effective, but looks great when installed too!:

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Escort Cosworth Uprated Clutch:

Traditionally, most uprated clutches for the Escort Cosworth tend to be either a heavy duty organic or sintered menatl friction plate coupled to a clutch cover with a heavier clamping force.

The organic lined friction plates are easier to drive and feel more like a standard clutch but are compromised by their relatively low torque holding capacity. The sintered metal friction plate has a significantly higher torque holding capacity but is compromised by it’s aggressive engagement, judder and noise. In both cases, the uprated clutch cover springs provide a heavier feel to the clutch pedal.

A solution to the above issues is the use of the HKS GD Max multi plate clutch and light weight flwheel. The twin friction plates are sintered metal to provide maximum torque handling capacity and are engaged synchronously to provide a smooth operation. The doubling of friction material quantity reduces the need for heavy pressure plate springs, so the overall feel of the clutch is light, progressive and easy to use.

The problem is that HKS do not make a twin plate clutch kit for the Escort RS Cosworth so we had to engineer a kit from a Japanese engine to fit and work correctly.

This is the HKS GD Max twin plate clutch kit:


The standard flywheel was engineered to accept the HKS GD Max clutch kit:

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One of the engineering challenges to over come was to convert the stardard “push” type engagement to a “pull” type and become hydraulically operated:

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We think that this is the first time in the world that the HKS GD Max twin plate clutch has been successfully installed in an Escort RS Cosworth.

In operation, we can report that the clutch biting point is exceptionally smooth and light. Mission accomplished!


With the engine fully assembled, Here is the uprated Escort Cosworth engine being re-fitted into the car:

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Installation of HKS SSQV Dump Valve:

The HKS SSQV dump valve is probably the best type available as they are very high quality and do not leak. HKS do not offer a dump valve kit specifically suited to the Escort Cosworth so we manufactured our own installation components.

Here is the special SSQV flange welded onto the intercooler pipe:

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Here is the HKS SSQV dump valve fitted to the Escort RS Cosworth:

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Here are some pictures of the uprated Escort Cosworth engine fitted:

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To find out about our ECU and tuning developments, please go to this blog

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