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MG MGB Technical - Valve Clearance
|I know the book calls for 13 thousandths cold, but the valves are very noisy there. When warm, 10 thou still allows you to hear the valves but not overly loud. Does anyone else share this adjustment or do you all prefer to go straight by the book?|
|Check that the tips of the rocker were it hits the valve stem is not worn and that the rocker arms don't have worn bushings. Normally theye really should not be loud enough to bother you with the stock settings.|
|Mine were noisier on the strict 'rule of nine points'. But now I adjust them at the position of the greatest gap, which for some reasons is one side or the other of the strict point for the back few valves, and that has made them a bit quieter, although I can't say they were that noisy anyway. Grooved rocker pads is the usual cause of excessive gap, which is what the Clikadjust was designed to get round, although I've never used one. Personally I wouldn't go below the book figure (I adjust cold and use 14 as a go and 16 as a no-go, easier to judge than 15). One thing that intrigues me is that the hydraulic lifters on my V8 take up *all* the free play, but even the hot figure for the 4-cylinder is still 13 thou, and the cold for the 1500 midget is even less than that. Considering it seems only to vary by 2 thou hot to cold, a further 13 thou as a 'safety factor' seems way over the top. You have to consider lift as well, reduce the gap and you increase the lift, so you may get other problems.|
|Paul Hunt 2|
The camshaft is cut differently - for solid tappets there is a ramp from the base circle up to the opening side of the lobe, it is designed to close the gap relatively gently so that the clearance is zero at the start of the cams opening side at the correct time.
The hydraulic camshaft has no ramp, it goes from the base circle straight onto the opening side of the lobe.
It is very important to use the correct valve clearance - to tight and the valve will not close properly and the exhaust valves will overheat, too loose and the tappet hits the opening side of the cam causing wear. In both cases you will lose power.
|Chris at Octarine Services|
|Chris - thanks for that, personally I intend to keep both mine by the book. But maybe those people who espouse fitting solid followers to V8s, and perversely hydraulic to 4-cylinders, aren't telling us the full story, as I don't recall any warnings to change the cam to the other type at the same time.|
|Paul Hunt 2|
This thread was discussed between 08/10/2007 and 10/10/2007
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