Cylinder Head Tuning & Rebuilding

Your cylinder head(s) are responsible for allowing both the air/fuel mixture to enter the engine and hot exhaust gasses escape the engine. This is generally achieved via poppet valves which open and close in accordance with the properties of your camshafts.

We work the inlet and outlet passages to enable better engine 'breathing', helping to generate additional engine power though better efficiency - particularly with older engines. In addition to this we reface (skim), pressure test (for cracks and leaks) and re-grind valves to ensure your head is ready to fit. The only work not included in our prices is remedial engineering work deemed necessary by our engineers - typically replacing snapped studs or damaged valve seats. This work is only undertaken with your prior consent.

Our engineer is a member of the Federation of Engine Re-manufacturers.

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Please click on a link below for additional information about the processes involved in our standard specification gasflow.

Cylinder Head Tuning:

Cylinder Head Rebuilding:


Removal & Smoothing of Casting, Pitting & Boring Marks

All marks left from the cylinder head manufacturing process are removed from the inlet and/or exhaust ports, leaving smooth surfaces with minimal obstruction to the flow of air, fuel/air mixture and/or exhaust gasses. Where appropriate, exhaust ports are widened at the uppermost point, where the fastest flow of hot exhaust gasses occurs.

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Valve Throat Pocket Smoothing & Widening

The part of the cylinder head between the valve guide and the valve seat is known as the ‘throat’ ‘bowl’ or ‘pocket’. We remove, smooth and blend in the marks caused by the initial factory bore and smooth the area around the valve guide to allow faster movement of gasses past it (where gas movement is at its fastest). This is the single most important modification point in a modern multi-valve cylinder head.

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Valve Guide Boss Re-Profiling

The valve guide boss is essentially an obstruction to the flow of gasses. A faster flow of gas occurs by machining a sharper edge to the front of the guide to ‘split’ the gasses.

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Port Matching to Gaskets, Inlet and Exhaust Manifolds

Where appropriate, the ports of the cylinder head, inlet and/or exhaust manifold are widened to eliminate obstruction caused by an overlap at the join. This can seriously rob power form an otherwise well-designed engine.

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Valve De-Shrouding

The walls of the combustion chamber are potential obstructions to the flow of gasses into the cylinder (particularly during the induction stroke where improvements to volumetric efficiency are made). Where appropriate, the walls of the combustion chamber are cut back at an angle (within the boundaries of the head gasket firing ring) to unmask the valves, and assist the quick dissipation of fuel/air mixture into, and exhaust gasses from, the cylinder.

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Exhaust Polishing

After the surface of the exhaust port has been removed of casting marks and smoothed it can be highly polished. This makes the exhaust gasses leave the cylinder head at a faster rate which contributes to reducing wear and tear on internal engine components, reducing the operating temperature of the cylinder head and increasing volumetric efficiency by reducing the amount of exhaust gas in the cylinder when valve opening overlap occurs.

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Inlet ‘Ribbing’

After the inlet ports are smoothed, they are given a very slight roughening in a ‘ribbed’ pattern to assist with fuel/air atomisation. Failure to do this causes fuel to leave suspension, condense on the inlet walls and dribble into the combustion chamber in non-combustible droplets. This wastes fuel, increases exhaust emissions, reduces performance and washes lubricating oil from the cylinder wall.

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Valve Stem Reduction/Removal

The valve stem (particularly on an older engine) is a considerable obstruction to gas flow within the port. Even a slight reduction in the length of protrusion into the port produces a noticeable difference during driving. Complete removal of the protrusion is the preferred option for rally, track and race use. Generally, complete removal of the protruding valve stem reduces the cylinder head life to about 15,000 miles and as such is not recommended for road and day-to-day use. Exhaust valve stems are rarely, if ever removed as they help to absorb considerable heat from the exhaust gasses. Modern multi-valve engines often have very small valve stem protrusions and little benefit is obtained from their removal.

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Combustion Chamber Polishing

The area of the head where the spark plug ignites the fuel/air mixture is called the combustion chamber. Polishing it exhaust gasses can leave the cylinder faster and reduces the negative ‘insulating’ effect of the coking up process.

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Valve Face Cleaning & Polishing

Cleaning and polishing the faces of the valves improves gas flow past their surfaces and contributes to preserving their longevity.

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Performance Three Angle Valve Seats

By cutting a further angle (or angles!) into the valve seat, considerable improvements to horsepower are obtained, particularly at lower camshaft lift where the valve is located very close to its seat and gas flow is otherwise restricted. All our 45 degree seats are complimented with both a 30 degree top cut and a 60 degree undercut.

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Cylinder Head Re-Facing (skim)

The cylinder head is measured to detect any warping or bowing and is precision milled on a lathe to remove imperfections accordingly. This is a standard procedure when re-fitting any cylinder head and is paramount to engine longevity.

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Chemical Clean

The cylinder head is pressure washed with industrial solvents to remove most grease, grime, oil, swarf, coke and carbon deposits.

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New Valve Stem Oil Seals

The oil seals located at top of the valve stem are replaced to reduce oil consumption and prolong engine life.

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Valve Grinding and Lapping-In

The valves are ground into the valve seats to match the joining faces together. This prevents loss of compression and prolongs engine life.

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Pressure Testing

The cylinder head is pressure tested to 7 bar to ensure that there is no loss of compression from ill-mated valves and valve seats or cracks in the cylinder head itself.

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High-Compression Skim

If you wish run your engine on high-octane fuel you will need a high-compression skim to increase the compression ratio to a level where detonation does not occur. We can advise the correct compression ratio for your engine and choice of fuel and offer a suitable skim.

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