Maintenance of your old-timer Volvo
In order to have continuous enjoyment of your Volvo, it is important to maintain it thoroughly. A few important points are valve clearance and the ignition. These will have to be re-adjusted every 10,000 km. When the car runs on LPG and the head does not have hard-seating valves then it is wise to re-adjust the valves every 5,000 km.
Heat transfer between valve and valve seat
A valve in closed position must close off the seat properly. Due to combustion in the cylinder, a high temperature will arise. In addition, the valves will increase in temperature and will transmit heat to the cylinder head when in closed position. The valves are produced from steel and like any metal the steel will expand when heated. Therefore, it is understandable that the valve steel will enlarge slightly. When the car runs on LPG or unleaded petrol, then the valves will get even hotter than when run on leaded petrol. For this reason, it is advised to prepare the cylinder head for the use of LPG/unleaded petrol by moulding the hard-seats.
Valve clearance imperative
In order to handle the expansion in the ovh-motor (overhead valves since the 50s Volvo often makes use of OVH-motors) some clearance will be left between tumbler (?) and valve handle. If one does not allow this clearance, then, due to the expansion, the valve will no longer close off. Furthermore, heat transmission from the valve to the seat will no longer happen. Because of this, the temperature of the valve will become too high and the valve will burn.
The valve clearance cannot be too big as the cams will open the valves later, will close them earlier and op top of that the cams might not raise enough. This will result in a reduction of the cylinder charge a reduction of engine efficiency. On top of that, the engine will make more noise.
As the material and the masse of the cylinder head and the valves differ, the degree of expansion will be different. Therefore, the producer indicates an engine temperature for when the engine has to be adjusted. It is also possible that two values are registered: one for the engine in cold condition and another one in hot condition. With standards B16, B18, and B20, it does not really matter at which temperature the adjustment takes place.
Feeler gauges are thin plates of hard steel with a precise thickness. When the valve clearance of an engine has to be adjusted at 0,40mm then we can check this clearance by feeding a feeler gauge between tumbler and valve handle.
Adjustment of the valves
The pistons 1 and 4 and pistons 2 and 3 of four stroke Volvo-engines (B16, B18, and B20) are equal in the uppermost position whereby the one cylinder is on compression and the other at the end of the exhaust stroke, beginning intake stroke.
The method that is often used is the one of twisting the camshaft until a cylinder is about to tumble and so the corresponding cylinder is at maximum clearance to get it adjusted. A cylinder is about to tumble when the one valve is about to go down, and the other valve is about to go up. A simple rule of thumb is that the cylinders must be at five. This means when cylinder 1 is about to tumble, cylinder four can be adjusted and vice versa.
The actual adjustment of the valves is the adjustment of the clearance between valve handle and tumbler. This clearance, as stated in the adjustment data of the engine, will differ from engine to engine. This clearance can be checked with feeler gauges. If two sizes are indicated, then the biggest size is used as rejection size. This means that a feeler gauge of that thickness will not fit or with major difficulty. If there is just one size indicated, then the rejection size will be 0,05mm thicker.
Within Volvo engines, the clearance will be adjusted at the camshaft side of the tumbler by twisting a small bolt with a screwdriver and after adjustment to lock this bolt with a nut with a wrench width of ½ inch.
Please do not forget to recheck the clearance after adjustment.
Maintain also other parts and areas of your Volvo.
Brakes, change oil, ignition, lights, tyres, etc.etc.