Renault F4R slipper follower
Belgium based high performance valvetrain specialist Cat Cams NV is pleased to announce a replacement finger cam follower package for the highly popular 2.0-litre, 16-valve Renault F4R engines as used in the Clio 172 / 182 / 197 and 200 models. In standard form the original RenaultSport valvetrain limits the F4R’s power output to around 260 bhp and 7800 rpm, because the standard roller finger followers are a known weak point and are not designed for prolonged high engine speeds. Therefore Cat Cams decided to redesign the F4R’s valvetrain following extensive CAD examination of various layout options.
Cat Cams settled on using new, bespoke finger cam followers that feature sliding contact. To ensure that these followers remain aligned on the valve top, the original RenaultSport F4R hydraulic lash adjusters are replaced by Cat Cam’s solid inserts, which are connected and locked by a common shaft. This shaft also acts as the rotation axis to make it impossible for the cam follower to leave its pivot.
The exact geometry for the new sliding finger followers was determined using Cat Cams’ dedicated in-house software for detailed motion analysis, while Finite Element Analysis (FEA) software was used to optimise strength, stiffness and weight. Main target parameters included: system clearance for 15mm valve lift, and a 40mm contact diameter for the virtual equivalent bucket tappet. Finally, a default range of cam profiles was developed, again using state-of-the-art cam design software that is continuously being developed on the premises since 1998.
With the new Cat Cam’s set up, the valve clearance on the F4R motor is set using lash caps with an extra long 4mm skirt sliding over the valve tip, and dual valve springs (manufactured by PAC Racing) with lightweight steel retainers and spring seats complete the kit.
Installation of the Cat Cams F4R finger cam follower setup requires a slot be machined in the cylinder head between the spark plug hole and the cam bearing, simply to provide the required clearance for the connecting shaft.
Ken Stessens, responsible for cam design and product development, testifies from own experience: "A simple manual milling machine with tilt table, a bullnose tool and 2 hours of hassle-free labour is all it takes to install the new cam follower hardware."
Once the Cat Cams RenaultSport F4R engine finger cam follower setup is installed, the high rpm potential of the engine can be fully realised and the valvetrain ceases to be a weak link. This theoretically endows the F4R motor with 9,000 rpm / 300 bhp plus potential when built using upgraded forged crankshaft, connecting rods and pistons.