Building The Legend – Quad-Cam V12

Work continues on our own quad-cam V12 ….

The following slideshow shows assembly of the first prototype. It is CNC-machined from hard resin as a precursor to casting in alloy:

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As confirmed previously, the plan is to end up with a quad-cam V12 which is inspired by (but with no attempt to exactly replicate) Jaguar’s prototype racing V12 as installed in their 1966 Jaguar XJ13 Le Mans Prototype. We aren’t trying to re-invent any wheels here or produce anything approaching “state of the art” but, instead, produce a reliable fast-road/race engine which celebrates and is inspired by the basic architecture of Baily’s 1960’s prototype quad-cam and legendary Jaguar XK 6-cylinder engine.

To this end, we are setting ourselves some basic ground rules:

        • Whilst Being inspired by the basic architecture of Baily’s quad-cam (as well as other engine designs of the period), opportunities to improve gas flow, combustion and overall efficiency in the light of current knowledge will be taken. Whilst cosmetically similar, these will not be exact copies of Jaguar’s 1966 Le Mans Prototype XJ13 quad-cam prototype engine – instead, they are inspired by this engine.

        • As was the case with the original 1966 Jaguar XJ13 Le Mans Prototype engine, cam drive will be via duplex chain as original (Incidentally, Jaguar’s rebuilt “original” XJ13 no longer has the engine installed in 1966 and now has gear-drive to the cams which was never the case in period and during active development).

        • Two-valve, hemispherical head design.

        • An option of fully programmable fuel injection & ignition (prototype quad-cam uses a pair of 6-cyl distributors and Lucas mechanical fuel metering unit).

        • Normally aspirated

    First Steps

    Because we are starting with an almost clean sheet of paper, we have the opportunity to go back to first principles and consider things such as optimal valve sizes, port configuration, charge movement and spark-plug positioning etc.

    The first step was to draw up a pair of heads combining a typical Jaguar SOHC V12 mounting face with a basic Jaguar XK 6-cyl DOHC design just to see if everything could be made to fit. After all, we don’t want to end up with head studs coinciding with inlet/exhaust ports! Also, we needed to make sure it was practicable and possible to mate up with oil and water passageways. There are also practical considerations to consider such as being able to access head nuts – bearing in mind each SOHC V12 head is fastened down by four rows of head studs but only two in the 1966 Jaguar XJ13 Le Mans Prototype quad-cam and XK 6-cyl.

    This is what we took our inspiration from:

    Building The Legend, Jaguar, XJ13, Neville Swales, E-Type, Classic Car, Jaguar XJ13, Jaguar Heritage, Jaguar Classic, C-Type, D-Type, XKSS

    SOHC V12 Head and 6-cyl XK engine accurately captured in CAD
    © Neville Swales

    The V12 head is not only longer than the 6-cyl head, but the bore positions are different. Positions of water and oil passages are very different between the XK 6-cyl and SOHC V12. The biggest challenge was combining the two heads so that the V12 stud pattern was maintained. It became evident very early on that the new quad-cam engine will have unique cam covers as well as custom cams. Fortunately, some items can be sourced “off the shelf”.

    The following pictures of the Jaguar XJ13 Le Mans Prototype quad-cam V12 show what we took our inspiration from:

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    Prototype Quad-Cam – RH Head
    © Neville Swales
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    Prototype Quad-Cam – LH Head
    Note offset inlet ports and recessed access to spark-plugs
    (a pig to get at when fully assembled!)
    © Neville Swales
    Building The Legend, Jaguar, XJ13, Neville Swales, E-Type, Classic Car, Jaguar XJ13, Jaguar Heritage, Jaguar Classic, C-Type, D-Type, XKSS
    Prototype Quad-Cam – LH Head Detail.
    © Neville Swales

    In contrast to the 6-cyl XK head and the SOHC V12, oil is fed to the quad-cam heads via a drilling passing from the gallery to each head.

    The following pictures show the general layout of these initial designs. They are just preliminary designs with no attempt to optimise things like port configuration, spark-plug location etc. They showed it would be possible to design our own heads which would bolt straight on to a typical SOHC block. Discussions with a local foundry highlighted considerations we need to build into the design. Further discussions with pattern-makers confirmed it will be possible to produce the necessary patterns etc.

     

    Building The Legend, Jaguar, XJ13, Neville Swales, E-Type, Classic Car, Jaguar XJ13, Jaguar Heritage, Jaguar Classic, C-Type, D-Type, XKSS
    Initial design – no attempt at this stage to optimise port location/configuration
    © Neville Swales
    Building The Legend, Jaguar, XJ13, Neville Swales, E-Type, Classic Car, Jaguar XJ13, Jaguar Heritage, Jaguar Classic, C-Type, D-Type, XKSS
    Experimenting with spark-plug location – improved access as well as better positioning in combustion chamber.
    © Neville Swales
    Building The Legend, Jaguar, XJ13, Neville Swales, E-Type, Classic Car, Jaguar XJ13, Jaguar Heritage, Jaguar Classic, C-Type, D-Type, XKSS
    Note positions of outer studs for SOHC block on exhaust face.
    Round exhaust ports as opposed to rectangular ones on the  6-cyl head.
    © Neville Swales
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    Experimenting with design for maximum coolant flow and reducing overall weight. 4.5mm wall thicknesses.
    © Neville Swales
    Building The Legend, Jaguar, XJ13, Neville Swales, E-Type, Classic Car, Jaguar XJ13, Jaguar Heritage, Jaguar Classic, C-Type, D-Type, XKSS
    Further investigation of inlet port location and optimal valve angles to give maximum valve size.
    © Neville Swales

    More to follow …..