Wildcat Cylinder Heads


An over view on the application for a Rover V8

Wildcat cylinder heads were originally developed and produced by Ian Richardson in the early 2000’s. Ian produced these largely on a low volume bespoke basis and so there are a number of evolutions and versions already existing out there. Be careful if buying second hand! These were variously described as stage 1, 1X or 2, but this designation had much to do with application rather than performance. For example Ian produced a number of special 4 inch bore cylinder blocks, and type stage 2 heads were developed for this application.

ACR Wildcat cylinder heads are developed for retro fitting to existing Rover V8 engines with 94 MM or bigger cylinders or of course as part of a new build. Now produced on new CNC tooling, reliable foundry processes, and with the benefit of the culmination of Ian Richardson’s and ACR’s experience, testing and development.

The standard valve sizes ACR have chosen are a 1.940” inlet, and 1.600” exhaust, which works especially well on the now common 96 MM cylinder bore format. This leaves sufficient material between the valves for durability and best compromise with valve to cylinder wall shrouding.

Ian identified the problems he wished to address with the Rover head for high performance use.

  • Valves offset from the centre line of the cylinder limits valve size.

  • Very little casting material to support valve seats, head gaskets etc, or creative re-porting of tracts.

  • Lightweight valve train unsuited to higher RPM or heavy valve springs.

  • Open style combustion chambers with little squish.

  • Low port entry and exits limits airflow potential and is the main reason why Rover engines are so difficult to get good BHP from.

The Wildcat head address the limitations of the Rover cylinder head for a true high performance engine.

  • Biggest possible valves on the centre line of the cylinder.

  • Lots of metal in the casting to support the valves, seats and guides, and provide as much rigidity as possible on the deck face for reliable gasket sealing with high compression ratios and cylinder pressures.

  • Small block roller Chevy valve train. Massive array of off the shelf parts at low cost.

  • Squish style open chamber with spark plugs directed at the hottest part of the chamber for high compression detonation resistance.

  • Raised inlet and exhaust ports to improve flow efficiency of the ports.

Should I use Wildcat heads for my application?

It would be simple to simply say yes, take the sale and clear up the mess afterwards.  If you are building an engine for moderate performance use, sticking with OE injection ECUs,  mild hydraulic camshafts, stock Rover inlets, automatic gearboxes, Range Rovers etc then the answer is no. Our CNC ported Rover head would be a far better choice.

If you are stuck at the low 300’s BHP and want much more, prepared to do the work to fit (or have a proper budget to pay someone else) then you will require Wildcat heads to reach the next level of performance.

Will Wildcat cylinder heads fit my application?

  • The Wildcat cylinder head will bolt on to a 94 MM and bigger Rover V8 cylinder block. Slightly longer hold down studs are needed as there is more metal thickness in the Wildcat head. The valve cut-outs to clear pistons will need to be checked and moved.

  • Exhaust flanges are the same stud layout as the Rover, but move upwards slightly. Check your exhaust can accommodate this movement. As you will be using an aggressive cam with lots over overlap you will need a tuned length extractor exhaust system.

  • Inlet ports move up and studs are tapped parallel rather than 15’. This move is the reason why Wildcat heads out perform any other head.  A Rover inlet does not directly fit! You have three choices from Wildcat: 4 barrel Holley type, Injection throttle body or IDA Weber style inlet manifolds. Alternatively Rover manifolds can be fitted with the use of adapters, but little point unless your Rover manifold is very well developed, or of the multi throttle type.

  • Valve Train. Uses Chevy small block stud mount with lubrication through hollow pushrods. This generally means using Chevy followers (lifters) with 5/16” ball ends. The great news is you have a massive choice of valve train, rocker ratios etc, at incredibly low cost. One would expect you will be using a solid mechanical tappet (lifter) but hydraulics with oil feed for hollow pushrods will work too.

  • Inlet gasket. The traditional Rover all in one valley gasket no longer applies. Inlet manifolds fit directly to the heads with modern sealant such as Loctite 5980. The valley is usually sealed with a cut down Rover inlet gasket, or an aluminium custom cover.

  • Spark plugs and leads. Wildcat heads use standard 14MM plugs with small hex bodies. NGK in the 6 heat range have been found to work very well in 400 BHP engines.

  • Rocker covers. The pattern is as per the original Buick 350. Wildcat produces attractive cast alloy covers at low cost. Catch tank setup is required to collect inevitable oil mist carry out.

  • What spec parts to fit? ACR stock valves, valve trains, spring etc for high performance use and at low cost. These are tried and tested in sub 7000 RPM race engines and quite suitable for a high performance road or track day car. For a full on race engine, one now has a massive choice of titanium valves, beehive valve springs,  and of course an array of lightweight super strong valve trains.

  • CNC Ported or as cast? Up to you! They will definitely need porting one way or another, and there’s lots of metal to play with. ACR have CNC programs to machine the ports and / or combustion chambers at extra cost. This will get you into a good working setup and the flow data is available.

  • Camshaft. ACR has had good results with “248” and “256” flat tappet cams, but there is a new generation  of roller cams which give exciting possibilities! Make sure your followers (lifters) have oiling feed for the rockers as per small block chevy.

  • Compression ratio. The primary considerations are camshaft choice, fuel choice and manifolding. Typically you can go higher than is possible on a Rover head. With a solid “248” camshaft  Wildcats work well on 11:1 CR and more, even on Supermarket 95 RON fuel.

  • Bottom end.  Achieving 400 + BHP, which is the starting point with a Wildcat setup requires a carefully constructed bottom end. Bearings and oil pressure are your focus. Don’t think a 7000 RPM 400+ BHP will stay together with anything less than 50 PSI, and ideally 65 PSI would be better. ACR stock 270’ grooved main bearings which give more lubrication to the big ends, of which the 5-6 pairing are at most risk. Sticky tyres and G force, or three dimensional antics of off road sport require careful thought on how you will keep the oil flowing through your engine at all times!

  • Cooling. Wildcat heads have little difference for cooling purposes. More power = more thermal load. Some Wildcat inlet manifolds will require customer fabrication of outlet systems.

  • Contact us. Please do not hesitate to contact us with regard to any query relating to ACR products and services. Advice above is a general guide and only given to assist with the early stage evaluation suitability of Wildcat cylinder heads for a project.