The Serdi System was 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Although now superceded by the Serdi 5, the Serdi 100 remains the bench test for all other seat cutting machinery.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. 

Our Cylinder Head Shop maintains a Serdi 100 . One of only a hand full of head shops to so in the world, including Formula One teams not available to the general public. The same basic principles apply to both Serdi 100 and the newer Serdi 5, the Serdi 5 has further advantages of accuracy of most interest to owners of complex mutli-valve and multi-cylinder engines, and motor sports teams looking to exploit the finest tolerances and most up to date equipment. See below.

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 carbl or through a Turbo, engines owe their high efficiency to precision machining of the cylinder head. There is no more important few millimeters 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. See below;

Grinding and lapping do not give an engine top performance, or for that matter even their original 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 no 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. See below;

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 and consequently the designed original or race specified qualities. During running, the valve will settle perfectly as the finish of the valve seat will not have been spoilt by grinding or lapping. See below;

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. See below;

Centering 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 my 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 below;

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! The best seat 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.

The Advantages

• 3 or even 5 angled seats can be perfectly finished in one operation.
• Due to the automatic and perfect centering, 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 center 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.

Comparisons

Costing over 38,000 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.

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

Everything You Ever Wanted to Know
About Having Your Seats Changed...

- Serdi-Style -

but Were Afraid to Ask.

What does this mean in practical terms?

• Racing heads that can run 3 seasons and still not need a head job, still measure up under factory specifications. Not good enough? How about classic engines such as BSA A50s doing 50,000 and, likewise, still not needing a head re-done? True stories from our file of happy customers.

• First the head is stripped, cleaned and vapor blasted. We check the original guides to make sure that they are tight in the head, fit new valves or guideline original re-faced valves as the customer requires

• The head is securely mounted on the elevated bed and the right pilot chosen with an interference to fit the chosen guide.

• A small spirit level is placed on top of the pilot and the bed rotated until it is perfectly perpendicular. The bed is then air locked so that it cannot move.

• The size of a cutter is determined by the size of the existing seat insert and/or the head size of the valve to be used. It is fitted into the pilot holder that is then fitted into the fully adjustable head. The head is then lowered, sliding the pilot into the guide and allowed to settle back and forward and side to side in a 360 degree field until a perfect position is found. It is then air locked into place.

• The cutting depth is set and the old seat machined out. In some cases, such as cast in seats, it is necessary to cut out the entire seat out. These are filled with weld and cut to suit a new seat. Each seat in a single head will be cut to with an thousandth of an inch of the same depth. 

• Important! In some head where the seats have been cut and pocketed, generally engine remanufactures blend that seat outwards resulting in a loss of capacity of the combustion chamber, extra stem protrusion and weaker spring pressure. Do not tolerate this. In such scenarios, The Cylinder Head Shop will, where possible, will instead fit an oversize seat, blend it into the chamber bringing back the original capacity and depth.

• The old seats are cut out as new seat housings are counter-bored. The head is heated and new silicon steel rings are set to an interference fit according to the design and casting technique, wall strength and thickness, material and age. This kind of knowledge is not readily available and comes from the basis of years of data based hands on experience with the widest selection of heads. 

Silicon Rings Made to Size

• Important! Where a head has been heavily skimmed, radically ported or oversized seats fitted, special attention has to be taken. These criteria will determine the fit. If your engineer does not know this.

• Beware! Every head has its own weakness and pitfalls. Many old heads are made of brittle alloys and many old engineers are stuck in the mud about how things ought to be done. Generally automobile remanufactures are not, in our experience, going to have sufficient experience of motorcycle heads or pay due attention to the process. Many customers of ours end up paying twice to have a head sorted out after it has been bogged. For car owners, this means we can offer you the highest quality of work and greatest appreciate of your interest in keeping alive old classic using start of art technology.

• Once the blank seat rings are fitted, consecutive cutting tip are fitted to the same pilot as the top of the new seat is blended to match the combustion chamber, a 3 or 5 angel seat is cut and the internal diameter of the throat machined. This process might require as many as 6 different tips to be fitted. 

• In some head, The Cylinder Head Shop will have to hand shape and fettle both ports and combustion chamber to match the accuracy of the new seats where old castings need equalized. We keep other tricks for problem cases up our sleeves.

• For high performance seat widths are narrowed and matched to valve faces.

• Between each cut the guide is cleaned to maintain fit of pilot.

• 3 or 5 angled seats are recognized to give best performance. Imagine for a minute a tap running with water. Place a finger along side the flow and see what happens, place two finger beside the flow and the water splashed out towards the both sides at an angle of almost 90 degrees. This is how an angled seat acts toward the flow of gases entering the combustion chamber. Place one angle, two angles, three angles and the mix fans out filling the chamber more fully. Each angle causes a small turbulence, a pressure differential, which spreads the flow outwards. The profile of each seat is matched to the valves used although we especially recommend the Nucleus Sport Elite range for improved flow.

• Seat fitted correctly do not drop out despite being hung up side down. In very rare cases that they do, you can blame the engineer's liquid lunch or Friday afternoon syndrome. On an old engine, a dropped seat can indicate a cracked head. This can occur at anytime without warning and is often discovered on a second hand head.

• Heads sometimes crack when new seats are fitted meaning that all the work has to be drilled out again, the housings welded, new seats fitted and re-cut again. In general, better the devil you know than the devil you don't, is our rule. Better to stick with the head you have and fix it than swap it for an unknown old head.