From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Valve and petrol pump issues, including tappet wear, camshaft squeaks, and petrol boiling problems.
| Identifier | ExFiles\Box 182\M18\ img055 | |
| Date | 14th July 1932 guessed | |
| -3- VALVES & FITTINGS. Double valve springs to Lec.2993. Improved Exhaust Valve E.93093 (S/SLV.) At a mileage of 4,000, No.6 tappet became noisy. It was found to have increased its clearance by .004" and after a further 500 miles it increased again .006". It then suddenly ceased and remained normal. No.7 tappet then started to increase, and up to the present has increased its clearance by .007". The only solution we have is the face of the tappet has started to tear up. We had a look at the tappet bearing surfaces while the crankchamber bottom half was down, and they looked rather scored. There is a camshaft squeak at approx 1000 engine revs. Both these tappets operate exhaust valves. We examined two of the valves, exhaust and inlet, and both were in a good condition. The strong valve springs are causing wear to take place on the bottom and top spring washers. There are deep grooves made by the ends of the springs. The tappet push rods are OK. H.R. PETROL PUMP Lec.2961. Clearance between Plunger E.82600 and Plunger Guide E.82601 increased to .0015" to eliminate Plunger sticking when oil is cold. A new pump head was fitted prior to this mileage, as the failure of the previous pump to deliver petrol from reserve was due to valves not seating correctly. We had at the beginning of the mileage a drying up of the petrol system at high speeds. This was traced to the close proximity to the chassis frame of the petrol pipe from the filter on the dashboard to the pump. The frame gets very hot from the exhaust manifold, and combined with the hot weather, the petrol in the feed pipe boiled. This is exactly what occurred with 25-M with the A.C. Pump. We cured the boiling by lifting up the pipe approx. one inch from the frame. This allows an air stream round the pipe and is sufficient to prevent the petrol from boiling. We have had no further sign of drying up during hard fast driving in very hot weather. We may mention here that the A.C. people recommend the isolation of the petrol feed pipe from the frame, from the tank to the carburetter. They had trouble with boiling in Africa due to the heat thrown up from the sands. At a mileage of 6000, the petrol supply failed. There was no positive evidence of the cause. No air leak had developed in the pipe lines. The rear filters had not sufficient fluff on the gauze to cause a stoppage. | ||