L20 s.w.c. ~036"M.S. VI APPRO A.5766A Fig. 6 Detail of oil sump baie plate Gearbox dipstick and oil seal To ensure that no oil leaks occur from the gearbox during the arduous conditions of competition work you can t a gearbox dipstick (Part No. ABC 3683) which is retained by rubber sealing rings. The one listed will need alteration by cutting off 2175 in. (61-9 mm.) and re-marking HIGH and LOW levels (as old dipstick); this will then make it suitable for the MGB gearbox. Also ascertain if the front gearbox cover is tted with a high-duty mainshaft oil seal (Part No. 22H 475); at the same time check the front gearbox cover (in which the seal is mounted) for perfect atness and ret with jointing c0m- pound. This will ensure that no gearbox oil will get through onto the clutch facings. Oil pump Standard The oil pressure may be increased by packing the oil relief valve spring; this is done by tting a circular steel packing of ii in. (12-3 mm.) dia. in the end of the release valve cap and behind the relief valve spring. These packings may be of -100, 200, -300, or 400 in. (254, 5-08, 762, or 1016 mm.) thick, or multiples of the -100 in. (2-54 mm.) packing can be used. Under the cap two bre gaskets are tted; one of these can be removed, or, better, both removed and replaced with one copper gasket (Part No. 6K 431). Between 70 and 801b./sq. in. (4-92 and 562 kg./cm.) and up to 1001b./sq. in. (703 kg./cm.) is a good pressure and dropping to 30/40 lb./sq. in. (2711/2~81 kg./cm.) is satisfactory. Sometimes the oil pressure increases up to, say, 5;500 rpm; and drops off in pressure beyond this speed. This can be prevented by machining the pump cover and making twin inlet ports to the pump. (See Fig. 7 to machine early pumps). A point which should be carefully checked is the oil pump strainer. The threaded attachment plate is spot-welded to the inside face of the strainer top plate. If the strainer top plate is not at, or if the attachment plate has not pulled up perfectly to the under side of the top plate, an air leak can occur between the attachment plate and the top plate. Ensure that the top plate is at over the gasket area, and to make sure that no air leak can occur carefully warm the whole strainer up and tin around the hole in the top plate to the attachment plate so that the bottom corner joint is sealed. Under normal conditions this position is under oil level, but when oil surge occurs, as in competition work, it may become uncovered. Oil lter It is not essential, but it gives some slight improvement in the oil ow, to machine an undercut in the face of the top casting of the lter bottle; this allows an unrestricted ow of oil from the square feed hole. (See Fig. 8 for details.) You must remove the circular plate from the casting to do this; lever the plate off carefully, and ensure that it is at before replacing and peening over. Torque wrench settings When tightening the cylinder head nuts to 50 ft. lb. (6-91 m. kg.) ensure that they are correctly and evenly tightened. The main bearing nuts should be tightened to 70/75 ft. lb. (9-68/10~37 m. kg.). Big-end bolts should be tightened carefully to 40/45 ft. lb. (5-53/6-22 m. kg.) only; overtightening to more than 45 ft. lb. (6-22 m. kg.) will only cause fracture of the bolts in operation. Tighten the ywheel bolts to 40 ft. lb. (5-53 m. kg.). Tighten the gudgeon pin bolts to 25 ft. 1b. (346 m. kg.) and clutch bolts to 25/30 ft. lb. (3-46/4-15 m. kg.). 457