MOTORING

Nelson Evening Mail, Volume LXI, 3 December 1927, Page 3

MOTORING

NOTES FOR THE OWNERDRIVER

AIR LEAKS AND BLOWOUTS CARBURETTER AND EXHAUSTTROUBLES Air leaki in the mixture pipe and manifolds and passages to the valve ports upset the mixture and cause misliring and imbalance of the engine. Leaks in the exhaust cause noise, and the same may be said about leaks in the jointing of the cylinder head, but in this ease Hie blowout affects the power of the engine in two ways. It releases some of the expanding gases which drive down the piston, but it also allows air to enter on the suction stroke, upsetting the mixture balance of the engine, and causing erratic running and misfiring in one or more cylinders. Air leaks in. the induction system cause erratic running and much loss of power, and the symptoms are often wrongly attributed to carburetter mis-adjust-ment. Generally, air leaks here are accompanied by a slight hissing noise, which may bo detected if the ear is put near the induction joints. The joints of tlie induction manifold should be remade with well-varnished washers, using gold shse. The thinner the washer the better the joint. But the faces must bo quite flat, and have been distorted by trying to open the joint with a cold chisel or screwdriver, or other pointed or chisel-shaped tool. Blowouts in the induction manifold will necessitate new copper and asbestos washers in the cases iwhero there.are four circular ports, or a fiat asbestos and copper washer, manufactured to shape and supplied by the car makers, in cases where the ports are of reetangui/ar. shape, and one washer is combined for all four (or three) outlet port?. When making a joint between the carburetter outlet flange arid the flange on tho uptake pipe (in the case of vertical carburetters) or tho face on the engine block, in the case of horizontal carburetters, the joint is best made with a simple soft copper washer, as it is advisable to allow the heat flow from the pipe or the. cylinders to pass to .the carburetter outlet. Copper washers are best when they aro soft, so that they can bed down in close contact with the flanges, to exclude the possibility of air inflow, winch would upset the mixture. If the washers are hard they can be softened by heating to a red heat by laying them on the top of a flat piece of red-hot iron, and then suddenly quenching in cold water after they have themselves reached the red-hot state. Blowouts in the exhaust piping should be immediately attended to, especially in the case of closed cars, or danger from partial suffocation may arise. They are easily detected by the extra sharp exhaust noises, almost, like cracking explosions. The exhaust pipe should be taken down, and new copper anil asbestos washers fitted, and the bolts in the flanges well tightened up again with lock nuts. Spring washers arc not much use under the nuts of exhaust flanges. The heat soon robs them of their spring,-, and-the joint becomes loose. |••• • ~.; ' .