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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).
Piston, ignition, and carburetor issues found during vehicle testing.

Identifier  ExFiles\Box 182\M18\  img054
Date  14th July 1932 guessed
  
-3-

Pistons. Standard Production type E.79365.

It was then found that the two top rings had seized up and that all the piston ring stops had worn away to such an extent that they had broken off, one portion was found underneath the third ring. The broken pieces had cut their way through the intermediate bands of the rings making a clear passage for the compression to escape through the piston. The remaining pistons were taken out and examined. No's 1 and 3 were in a good condition. No's 2, 4, and 5, the piston stops had gone, a piece was found under one of the rings. In these cases there was no further damage and they were replaced. The stops appeared to have been chattered away by the ends of the piston rings and had worn down to approx. 3/32" in dia. before finally breaking off.

There was .0065" thickness of carbon deposit on the centre of the piston and .017" at the edge nearest the exhaust port. There was a similar amount on the underside of the piston top. We obtained a new standard piston from our Paris Depot. The fit and the bedding was standard. We have had no further trouble up to this mileage. These pistons had done 8117 miles previous to this test.

At a mileage of 3600 we had misfires from the magneto ignition at 20 m.p.h. The plugs we are using are the Lodge HD.{Mr Hayward/Mr Huddy}3 These are being tried to overcome preignition troubles. In this respect we have had no sign of preignition during any of the sustained high speed runs. The plugs were reset from gaps of .015" to .020" and the misfiring ceased until 5000 miles was reached when misfiring again came on. The oxidization of the points appeared to be the trouble, as they were OK. after being cleaned. On the battery side they are still firing regularly.

CARBURATTER to LOP.M.S3075. SEMI EXPANDING - LeC.2972 - 3026-29

At this period we had erratic slow running and flooding of the carburetter. At 4500 miles it became very bad and engine choked when idling on the road. The cause was the float chamber needle failing to close. We could not find any foreign matter on the seating to have caused the trouble. Examination of the seating of the needle with a magnifying glass looked as if the cause was due to chattering, as the seating was rough. We lightly ground in the needle with fine paste then polished up dry, this cured the flooding trouble also the slow running.

There has been no trouble in starting up first thing in a morning, but the air temperature has been warm, i.e. 10°C to 15°C.
  
  


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