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Valve Clearance Adjustment-- Engine cold or hot? 145 140-160 1971

I just discovered that the valve clearances on my 1971 B20b engine are supposed to be at .020"-.022", unlike other B20s which are supposed to be at .016"-.018". Before I redo the adjustment, should I do it with the engine warm or not? Does it even matter? (I'm misfiring at the 4th cylinder at low rpms and am hoping this is the cause...)

Thanks!

Ben








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    Valve Clearance Adjustment-- Engine cold or hot? 145 140-160 1971

    Ben;

    To go along with the other good advice, when setting valve clearances on used engines, I suggest grinding down the width of the appropriate feeler guage, at the end (just narrower than the valvestem) so that when guaging, it doesn't bridge any wear present in the rocker surface (which a full width feeler guage would), giving an inaccurate measurement (equal to feeler PLUS wear depression).

    Cheers








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    Valve Clearance Adjustment-- Engine cold or hot? 145 140-160 1971

    It's best to dothem at operating temp. It'll help to keep you from setting them too tight.








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    Valve Clearance Adjustment-- Engine cold or hot? 145 140-160 1971

    As well as what the others have mentioned.... the easy way to do it is to pull out 2 feeler guages... on that is perhaps .020", and the other that is perhaps .016". Adjust them such that you can slide the thinner one in, but the thicker won't fit.

    Then you know you have it within specs. Of course, if your target is .020", then use a .018, and a .022...

    If one of your valves is too tight, it would cause low compression...which could explain the miss at idle. But... I would expect it would have to be quite a bit too tight....

    -Matt








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    Valve Clearance Adjustment-- Engine cold or hot? 145 140-160 1971

    My recommendation on B20 and B30 engines, based on several manuals and
    considerable personal experience, is that you should not set the valve
    lash at less than 0.020". B18s go at 0.018" because of their larger
    valve stems. A smaller clearance will prevent the valves from closing
    tightly enough and cause leakage, keeping the valves from cooling through
    their seats. The end result is erosion and cracking of exhaust valve
    seat faces. I don't think engine temp is too important for setting,
    as long as it is not extremely hot.
    --
    George Downs, The "original" Walrus3, Bartlesville, Oklahoma








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    Valve Clearance Adjustment-- Engine cold or hot? 145 140-160 1971

    Either will do.


    The quickest way to set them is to set the engine to TDC firing on number 1 cylinder. Then adjust valves 1,2,3 and 5. Turn the engine a full revolution, it is now on the number 4 firing stroke. Adjust valves 4,6,7 and 8

    Regards


    Pete







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