DISCUSSING AIR LEAKS

NZ Truth, Issue 1144, 3 November 1927, Page 13

DISCUSSING AIR LEAKS

Detection and Remedies

Explained

Air leaks m the petrol pipe, manifolds, and passages to the valve ports, upset the mixture and cause missfiring and unbalance of the engine.

LEAKS m the exhaust cause noise, and the same may be said about leaks m the jointing of the cylinder head, but m this case the blow-out affects the power of the engine m 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 with missfiring on one or more cylinders. Air leaks m the induction Bystem

make for erratic running and much loss of power, and the symptoms are often wrongly attributed to carburettor misadjustment. Generally air leaks here are accompanied by a slight hissing noise which may be detected if the ear is put near the induction joints. The joints © f the induction manifold should be re-made with well- varnished washers, using gold size. The thinner the washer the better the joint. But the faces must be .

quite flat, and not have been distorted by trying to open the joint with a cold chisel or screw-driver or other pointed or chisel-shaped tool. Blow-outs m the induction .manifold will necessitate new copper and asbestos washers m the cases where there are four circular ports, or a flat asbestos and copper washer, manufactured to shape and supplied by the ear -makers, m cases where the ports are of rectangular shape, and one

washer Is combined for all four (or three) outlet ports. ! When making a joint between the carburettor outlet flange and the flange on the uptake pipe (m the case of vertical carburettors), 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 carburettor outlet. Copper washers are best when they are soft, so that they can bed down m close contact with the flanges to exclude the possibility of air inflow,

which 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, arid then suddenly quenching m cold water after they have themselves reached the red-hot state. Blow-outs m the exhaust piping should be Immediately attended to, especially m the case of closed cars or danger of 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 and asbestos washers fitted, and the bolts m the flanges well tightened up again with lock nuts. Spring washers are not much use under the nuts of exhaust flanges. The heat soon robs them of their spring, and the joint becomes loose.