The home of the UK's greatest sportscar
15/09/2008
After studying the Speed 6 cylinder head Racing Green TVR felt that the costs involved in creating an entire new head design were not justified and that the overall design of the cylinder head was good and could be modified. With this in mind Racing Green TVR set about designing a structure that could be a retro-fit into an existing original TVR cylinder head casting albeit with a certain amount of machining.
By machining out part of the cylinder head casting originally used to support the finger follower shafts and spark plug apertures it became apparent that a sophisticated and accurate casting could replace this structure and allow the removal of all of the finger followers and their supporting shafts and their replacement with an inverted bucket cam design.
This design evolved into a high specification and compact aluminium casting which provides the location for the 24 inverted bucket cam followers and the required bearings to support the camshafts all of which would still fit under the existing original cam cover.
The existing oil feeds to the cylinder head are still used and provide the oil supply to the bucket carrier casting via O ring seals. The bucket carrier casting is rifle drilled internally ensuring that all cam bearings are fed with a much more direct lubrication system.
The buckets themselves are effectively splash fed with the excess oil from the pressure fed camshaft bearings. The design of the cam carrier ensures that the oil remains covering the buckets at all times hence ensuring lubrication at start up. The buckets are ultra light and based around a performance Cosworth solid lifter.
Once the design had been finalised and subject to software analysis the big step was taken and the casting patterns were commissioned and to ensure absolute repeatability were CNC machined from solid. This guarantees that all the subsequent castings are both accurate and dimensionally correct from the mould.
The castings are of very high quality with the molten aluminium being filtered prior to reaching the mould. Castings are heat treated and due to their length checked for straightness and then machined. The CNC machining process creates the bores for the buckets, all location points and the mounting arrangement for the cam shafts as well as the oil delivery system. The cylinder heads are machined to create the void to take this bucket carrier casting and to introduce the pick up points for the oil supply etc.
Each cylinder head is matched to a bucket casting and the cam bearings are then line bored as the final machining process.
The cam lobe design has been changed on a number of fronts as the original profiles are no longer applicable with this new Finger Follower Free design. Generating a similar amount of lift as the original TVR cam shafts the new profiles ensure good mid range torque and driveability.
The net result is a Speed 6 engine with all the hallmarks of a TVR engine, but with levels of refinement that were previously unthinkable. Don’t take our word for it but read the up a coming article in TVR Sprint magazine and see what others think!!!
“To drive...its just silky smooth. As others have mentioned, say a big hello to free-revving”
“The engine just feels so much lighter (which it is) and responsive it is incredible.”
“Oh my god, it is so smooth and solid”
“2nd, 3rd, down a gear again, and then, the final straight, up the revs, and oh my... Pulls like a train