Jonn began by carrying out a pre-delivery inspection on our 1968 Lotus Cortina. He inflated all tyres to the correct pressure and torqued the wheel nuts. The spark plugs were removed, cleaned, and re-gapped before the fuel system was filled with synthetic fuel. A road test was conducted, during which the vehicle was found to be holding back under acceleration. The car was brought back in for further investigation.
Jonn removed the tops of both carburettors to check and adjust the float height. After refitting the tops and carrying out another test, the issue persisted, resembling a misfire on cylinder 2. Work continued with the carburettor linkages, completing the reassembly of the rear carburettor and blowing out the jets. The wiring was also returned to its previous configuration, with the coil wired through the ballast resistor. Despite these steps, the symptoms remained unchanged.
Attention then returned to the front carburettor. Jonn removed its top and drained the fuel, taking out all jets for cleaning and blowing through each one before reassembly. After securely refitting the top and testing again, there was still no improvement. With Rob’s assistance, the air filters were removed and an attempt was made to balance the carburettors by ear, though the fault remained. Suspecting another underlying cause, Jonn allowed the engine to cool before continuing the investigation.
He then removed the rocker cover to inspect the camshafts and found that the lobes and tappet buckets on cylinder 2 were visibly worn. A check of the valve clearances showed the inlet valves were within specification at between 0.005 and 0.007 thou, and the exhaust valves should have been between 0.006 and 0.008 thou. However, the exhaust valve on cylinder 2 was reading 0.024 thou, indicating it was barely opening, while cylinder 3’s exhaust valve measured 0.002 thou, suggesting it was barely closing. The inspection confirmed wear to both cam lobes and followers. Jonn concluded that new camshafts and followers would be required and subsequently reviewed the necessary parts with John.
