UNLEADED CYLINDER CONVERSION

UNLEADED CYLINDER HEAD CONVERSIONS...

We are able to undertake cylinder head rebuilds for all Aston Martin models. All of our engineering work is carried out "in-house" on the latest state of the art equipment, by highly skilled engineers with many years experience of the marque.

At Aston Workshop we are able to offer the complete package for cylinder head rebuilds and modifications. Having invested heavily in the very best equipment available, we are able to carry out all of our engineering "in-house".  This combined with our extensive experience ensures each and every job is undertaken to the very highest levels of quality and at a reasonable cost.  

Complete cylinder head re builds / unleaded conversions can be carried out as a service, with safe transportation of your cylinder head worldwide. Or for complete peace of mind we can carry out the removal, refit, set up and test in our highly equipped workshops. 

Our "standard" cylinder head re build consists of the following

Initial strip and inspection

Chemical “de coke” dip and hot pressure steam clean

Further inspection of the cylinder head casting, including the measuring of camshaft follower bores, cam journals and cylinder head thickness

Pressure test of the casting at 40PSI

We then proceed with machining out the old valve seats using our Serdi valve seat machine. After the removal of the old valve seats, we are ready to bore out for the new. Our machine is equipped with "pre set" cutters to obtain not only the optimum level of interference but complete repeatability.

The cylinder head is then heated and the new unleaded compatible valve seats are frozen prior to installation. This procedure removes the risk of "broaching" the valve seat bores, which can result in incorrect interference fit and the valve seats falling out during operation! We then "top" and "throat" the seats to the required height and bore, prior to hand blending the ports, at which point the ports are "tidied" and re-shaped to improve gas flow.

The next step is to replace the inlet and exhaust valve guides. The casting is heated and the water cooled valve guides are installed using a specially formulated ceramic sealer. The casting is once again pressure tested to check the new exhaust valve guides have sealed correctly.

Having produced special cylinder head clamping jigs we are able mount the cylinder head rigidly on our valve seat machine with the camshafts fitted "in-situ".  This has two major benefits. First, the rigidity of the clamping arrangement allows the seats to be cut to an unrivalled level of accuracy and concentricity. Second, it allows us to machine the valve seats to exactly the correct height with the cam-shafts and cam followers pre-installed. With this method we have optimum tappet clearance without the need to machine the tips from the valves or swap cam follower buckets to achieve the correct "tappet" running clearance.

With an array of specialist tooling to hand we are able to create valve seat profiles based on your engine's requirements.

Due to the accuracy of our equipment and technique, coupled with high quality valve and valve seat materials, you will never need to reset your cam follower (tappets) running clearances again (under normal operation).  For more information regarding our valve seat guarantee please view our case study section- A NON MOVER BY THE ASTON WORKSHOP.

We then move on to the finish blending of the valve seats into the ports and combustion chambers, tidying ports, cleaning up inlet and exhaust manifold faces, re-tapping all threaded holes, cleaning up cam cover faces, cam journals etc. 

The next step is to machine the cylinder head face. This is carried out on our Rottler F65 engine machining centre. Using the latest Polycrystalline Diamond (PCD) cutters we are able to produce a level of surface finish and accuracy which is second to none. At this time we would also chamfer the combustion chamber to the required diameter if required. 

Cleaning of the cylinder head casting and all components then commences. Chemical and hot pressure wash followed by a hot pressure rinse and drying of the casting before we use a pneumatic vibrator (with the head inverted) to dislodge any small particles of debris which can be lodged inside the water jackets. All related parts are cleaned using a special chemical in our "clean" final build parts washer.

Final checks are then made, prior to assembly and completion of the re-build data sheets.

 

Parts included as part of the "standard" re build

Inlet valves

Exhaust valves

Inlet valve guides

Exhaust valve guides

Inner and outer valve springs

Unleaded compatible valve seats.

Additional parts

Camshafts

Camshaft follower buckets

Oversize valve guides

Studs

Distributor drive gear.

Further options which may be required

Machining for oversize valve guides and cam follower buckets

Clearance machining for up-rated camshafts

Line boring for cam shaft bearings

Welding and reclamation

Repair to damaged stud housings and threads

Machining and repairing of head stud clamping areas.

 

CASE STUDY

"High Torque" 4.2 Litre DB4 Engine

The brief was simple. Produce a DB4 engine with a large increase in both power and torque, but retain the original look of the twin S.U carburettors.

More...

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