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The Serdi 100

CHS Seat Cutting on Formula One Standard Equipment. The Serdi Systems were the first valve seat cutting equipment capable of producing the degree of valve seat accuracy required in today’s formula one racing engines and is widely used by a number of racing teams and leading manufacturers.

Although now superseded by the Serdi 5 & 7, the Serdi 100 remains the bench test for all other seat cutting machinery. It degree of adjustability makes it most suitable to working on classic vehicles due to the extensive range of angles and “one off” capacity.

The Cylinder Head Shop maintains a Serdi 100, along with a Serdi 5. One of only a handful of headshops to so in the world, including Formula One teams not available to the general public, and certainly the only shop in the UK. Although the same basic principles apply to both Serdi 100 and Serdi 5, the Serdi 5 has further advantages of accuracy of most interest to owners of complex mutli-valve and multi-cylinder engines, and motorsports teams looking to exploit the finest tolerances and most up to date equipment.

Grinding and Lapping Eliminated by the Serdi System Equipment … A Tradition that No Longer Corresponds with Today’s Hi-Tech Demands and Materials!

Serdi has met the craftsman’s, collector’s and racer’s concerns for ultimate precision, quality and reliability with the Serdi 100 valve seat cutting machine. The first machine to eliminate the age old and laborious techniques of grinding and lapping valves into seats. Chosen as a matter of form by original manufacturers of today’s top engine builders, The Cylinder Head Shop has pioneered the use of Tomorrow’s Technology for Today’s Classics. Simplicity, performance and perfection are the keywords of this revolution.

Beneficial for All Engines

Whether 2 or 5 valve, whether vintage or straight off the production line, whether breathing through an old Amal or through a Turbo, engines owe their high efficiency to precision machining of the cylinder head. There is no more important few millimetres of your machine but for those where the valves meet their seats. Whether the angle of the valve is 45 degrees, 30 degrees, 3 angles or 5, the contact and seal between the valve and seat can now not only be perfected but also stay that way through out the life of the engine.

Grinding and lapping do not give an engine top performance, or for that matter even their orginal performance back. Neither do they promise best longevity. In fact, it has been scientifically shown that these procedures simply destroy all surface structures and treatments even the geometric forms of the valves and seats.

Material science and technology has come a long way since the time riders had to hand lap valves in as a matter of course and yet die hard traditionalist still insist that this is the way it is done. Our results with the Serdi 100, and those of other top race teams argue otherwise. Ensuring a 45 degree angle on both the seats and the valves, using a Serdi 2, means that as the seats wear they wear they maintain their original geometric qualities.

When you can pull a bar of pressure under vacuum and have road heads coming back after 50,000 miles not needing re-working or race heads on their third season with, you know something special is happening but why is this?

Grinding and Lapping Destroy Surfaces

When grinding and lapping Surface A and surface B will match but take an uncontrollable form. The geometrical quality of the valve is destroyed, the qualities given by various heat treatments, machining or re-facing is lost. Most valves have some form of treatment and by grinding in this fashion, it is destroyed.

This means that the flow over the edge of the valve is interfered with losing performance and the quality of the contact between valve and seat in insufficient to secure good heat transfer between valve, seat and cylinder head. Heat is not transfer away efficiently and so builds up around the exhaust seat and along the valve in a damaging manner that causes increased wear to the engine.

When using a Serdi 100, a valve seat benefits from machining by a technique that allows it to regain a perfect geometry. Consequently the designed original or race specified qualities are restored or improved. During running, the valve will settle perfectly as the finish of the valve seat will not have been spoilt by grinding or lapping.

How Do We Do This?

Serdi Technology uses the real axis of each guide as a reference for machining the valve seat. An interference fitting pilot slips down inside each guide of each head in a total unique and individual manner, regardless of the angle of the guide in the head, regardless of whether the head has “settled” slightly, regardless of whether a new angle has been requested, any angle possible.

All of these can be accommodated thanks to the Serdi’s patented fully adjustable air bed below and infinitely variable air locked head containing a spherical joint that holds the pilot above.

Centring is automatic because of a frictionless air cushion under the work head and around the sphere. Automatic pneumatic locking insures accurate rigidity. A revolving pendulum movement of the spherical on the frictionless air cushion joint within the head further insures high precision. As the work head can move equally in all directions, it can finds the perfect position and balance; and a powerful constant torque DC motor mounted within it drives the cutting tips with strength and security unmatchable by hand.

The bed is supported by 4 legs and can be lifted and rotated 30% in all plains, side to side, and back and forward. Equally 60% in total.

Most seat cutting systems are like simple pillar drills with flat fixed beds. Fine for automobiles but not bikes and so on. This allows us to custom fit for all heads. A racing head will require an hour’s setting up before work even starts.

See, right. Notice Lower Bed Tilted at Bottom of Picture

The Difference

By using seat machining and finishing in reference to the real axis of the guide rather than a pre-set operator design we can eliminate all human inaccuracies and consequently guarantee a perfect precision finish every time, to every head. No more Friday afternoon jobs!

Good jobs are often done by hand held cutters such as the Mira but hand and eye cannot offer the consistent reliability of a Serdi cut due to strength of motor and infinite adjustability. Likewise operating systems with a fixed quill and table or weaker motors are too limited by these restrictions.

The Advantages

3 or even 5 angled seats can be perfectly finished in one operation. Due to the automatic and perfect centring, we can remove minimal amounts of material if required. Valve seats can be machined to exactly the same height in relationship in relationship to an independent fixed point, the cylinder head face or to the camshaft alignment. This means all heads regardless of whether they are flatheads, have Desmo drives or overhead cams can be handled to the same degree of uniformity and perfection. Precision engineering to less than .0002 of an inch

In Addition to the Bed Floating the Quill can Rotate Another 12 degrees

Guide Sag Causes Poor Machining

In this diagram the valve axis capable of being matched by the Serdi is marked as a straight line down the centre of the guide [1].

The axis as in classic centering by using is marked to one side [2]. This is caused by guide sag during mounting or by wear [3]. Often when guides are hammered incorrectly into the housing they distort and this is ignored.

Certain wear is also caused by the action of the rockers onto the top of the valves when they are fitted into poor quality or unlined guides with slack tolerances between valves and guides of around 3 to 4 thou.


Costing over £28,000 the Serdi 100 plus attachments is almost twice as much to purchase than its nearest competitor, the Serdi Millennium and remains the choice of tuning specialist the world over. It has a more powerful motor, more adaptable head and is more versatile thanks to the fully floating air-locked elevated bed that allows each head to be tilted to exactly the right angle to suit each guide.

Other Key Features

The Cylinder Head Shops holds a complete range of high quality carbide pilots for every size of engine, from 3.5mm to 20mm valves.

The Cylinder Head Shop holds a wide range of tungsten carbide cutting tips with special designs for accurate positioning and forming of every seat shape. Years of research, study and experience on the widest range of head imaginable, from model engines to aircraft, from veterans to development engines, has taught us the best design and material of tips to use. There are no manuals to teach you this.

For a list of head shops using Serdi Equipment, click here.
For a list of dynometer shops to help set up your engine, click here.

The Cylinder Head Shop holds a wide range of tool holders for all applications