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| Engine Rebuild Service Why do GGR always use a torque plate when reboring the cylinder block? What are the differences between each type of head gasket? I have heard of 'wire ringing' of cylinder blocks, what is this process? Why do you reface the cylinder head & block? What is the benefit of the high clamp cylinder head, stud & nut kit? Why do GGR emphasise the balancing of the engine, aren't all Cosworth engines balanced? Isn't the cam timing set accurately on production engines? If GGR rebuild my Cosworth road car engine, what do I get for my money? | |
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During the last ten years involvement with the Cosworth range of cars, GGR have built a large number of engines, to many different specifications. Development of our own Group A touring car engines saw an increase of power from a humble 380 BHP in original small turbo specification, to over 540 reliable BHP with the later RS 500 unit. Customer engines for ThunderSaloon racing, Group N Race & Rally, and other competition cars have also been built over the years. We have also built many road car engines, for customers not only in Britain, but all over The World. The standard specification engine rebuild incorporates the following minimum replacements: | ||
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Why do GGR always use a torque plate when reboring the cylinder block? | ||
It was an early discovery of ours that the cylinder bores distort alarmingly in the engine when the cylinder head is tightened down. The mis-shaped bores can then lead to excessive piston ring blow-by, and the piston to bore clearance is larger than necessary. Using a torque plate, we can guarantee round bores, and tighten up on piston to bore clearance, reducing piston slap, and improving piston ring seal. | ||
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GGR only use three different head gaskets. The first one is the YBO 611 head gasket; this is the original Cosworth Group A head gasket. Similar in appearance to the standard gasket but manufactured to a higher standard. We generally use this type of gasket on all mechanically standard, and engines fitted with a gas flowed cylinder head. | ||
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I have heard of 'wire ringing' of cylinder blocks, what is this process? | ||
It is an attempt to improve cylinder head gasket seal without using higher quality gaskets. A small groove is machined in the gasket face of the cylinder block around the cylinder bores, and material (usually welding wire) is fitted partially into this groove to give a pressure point on the gasket. We do not consider this a successful method for a number of reasons. | ||
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Over a period of time, as the engine components heat up, and cool down, distortion may occur. To guarantee a good seal at the cylinder head gasket, it is essential that the two mating faces are as flat as possible. We only remove the minimum material necessary to ensure this, to retain the maximum strength. | ||
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What is the benefit of the high clamp cylinder head stud & nut kit? | ||
In our early development of the Touring Car engines, we experienced problems with head gasket failure. We designed the stud & nut kit, and this resolved our problem. The studs are made from heat-treated alloy steel with a coarse thread on one end, and a fine thread on the other. The coarse thread screws into the cylinder block, using the complete depth of thread in the block. Above the coarse thread is a short plain section to accurately locate the cylinder head & gasket. In-between this and the fine thread at the upper end, the stud diameter is waisted down. This is to ensure that the clamping stress on the stud is spread over this complete length, not concentrated on a very small area (which could lead to breakage). The fine thread and matching dome headed nut will allow a far greater clamping force at a lower tightening torque.
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Why do GGR emphasise the balancing of the engine, aren't all Cosworth engines balanced? | ||
As is always the case with production built engines, everything is done to be within a certain tolerance of the ideal specification. | ||
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It is the same story as the balancing question; camshaft timing on the standard engine is within a certain tolerance. We set the camshaft timing exactly to the figures specified by Cosworth, using either adjustable pulleys, or offset keys. | ||
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If GGR rebuild my Cosworth road car engine, what do I get for my money? | ||
The first thing we have to do is remove the engine, (and if the car is 4-wheel drive, this will involve removal of the complete engine, gearbox & front suspension). The engine is then totally stripped, cleaned & inspected for wear & damage. The engine & turbocharger are then totally rebuilt as described above. After reboring & refacing, the cylinder block has all core plugs removed, is fully cleaned & lightly de burred. It is painted blue (traditional GGR engine block blue!) and new core plugs fitted prior to reassembly. All other components are cleaned, and where necessary, painted so that the physical appearance of the engine matches its better than new mechanical specification. Before the fresh engine is fitted back in to the car, the engine compartment etc. is steam cleaned. When the engine is completely installed, with spark plugs removed and engine management system disconnected, the engine is cranked over with the starter motor to pump lubrication oil around the engine. Once oil pressure is obtained, the engine can be started. We always complete the first 100 miles of running with a new engine ourselves, before asking the owner to finish the running in period of 750 to 1000 miles. Before the car is collected from us it has a full valet, and when the car is returned for its first engine service and boost set up etc. we only charge for the additional parts used in this service, there is no further labour charge. | ||
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Correspondence/Requests | ||