to the 4WD Ferguson P99 Formula 1 having a front engine layout, which could not accommodate exhaust pipes that merge with pipes from exhaust ports on the opposing banks on crossplane arrangement, but this project did not materialise. Later, such an elaborate crossplane exhaust system became known as "bundle of snakes" on the Ford GT40, but was a feature of FWMV Mk.I and Mk.II. This Mk.III developed at 9500rpm, propelling Jim Clark, Lotus 25 and Team Lotus to 7 wins, 7 pole positions, 6 fastest laps, and the World Championship title. Mk.4 was developed for 1964 with yet larger bore (72.4 mm) and shorter stroke (45.5 mm) with a larger exhaust valve (from 1.237" to 1.37") and 12:1 compression ratio to result in at 9750rpm. One-off Mk.5 was made with a larger inlet valve (from 1.35" to 1.40") for , which was delivered to Lotus and said to be used by Clark in the 1964 season. Mk.4 and Mk.5 scored five wins (three by Clark for Lotus, two by Gurney for Brabham), seven pole positions, and seven fastest laps. A one-off 4 valve Mk.6 had 1.04" intake and 0.935" exhaust valves, new pistons, cylinder sleeves and crankshaft, and had gear driven camshafts as opposed to the previous chain drive. This engine made at 10300rpm and went to Lotus during 1965. Another 4 valve one-off, Mk.7, was built with 1.107" intake and 1.043" exhaust and all the new Mk.6 parts for at 10500rpm, and was delivered to Brabham. However, these engines started showing reliability problems. Except for these two one-off 4 valve engines with characteristic ribbed cam covers, all the FWMVs used in 1965 season were 2 valve Mk.5 or earlier versions with various levels of upgrade. This was because Coventry Climax had started the FWMW flat-16 project, which was finally announced at the beginning of 1965, and had more than a handful in things needed to be developed or solved, so the 4 valve configuration on FWMV did not get completely developed nor did reach a series production. However, Jim Clark was able to win 6 championship races (3 with Mk.6), 6 pole positions and 6 fastest laps to become the 1965 World Champion. At the end of the 1965 season, the failure of FWMW project left Coventry Climax with no 3 litre successor to FWMV for the next season, so a 2 Litre version of FWMV was assembled using