MG Car Repair: lifters, cam lobe, valve adjustment

Question
I have a 1979 mgb with emissions off the problem is that one of my rocker arms cant be adjusted because it is to short. That is were i thought it might be worn cam lobe but when you get the pin down far enough without nut their is a clacking noise like the lifter is double pumping. Also if i let the pin loosen up where it is not touching the car gets hard to start i have good oil pressure, did a compression test and seem to be good and could this be a collapse lifter

Answer
Hi Adam,
First thing to do is lay a straight edge across the top of all the valves to be sure it is not a valve problem. After you have done that Remove that pushrod and another and compare lengths to see that it is not a pushrod problem. Then closely examine the rocker arm to see that it looks good and is exactly the same as the others. Then measure at the valve collar to head distance when the valve is opened on a good valve and adjust the bad one as far as you can and then turn the engine so as to open the bad valve as far as it will go and measure the valve collar to head distance. If it is off a good bit, you do probably have a bad lifter and cam. I have seen many bad lifters on MGs but never seen one worn down so far as to run out of adjustment. These are solid lifters so they can not collapse. And 99 of the time that a lifter is destroyed, the cam is gone too. I never seen the base of a cam worn away so as to make valve adjustment run out of travel.
Let me know what you find. A cam lobe can be worn completely away and it will NOT change valve adjustment at all.

If all that looks good then you can assume that the lifter is most likely the cause of the problem and you may as well pull it out to look at it.
Howard