on cars with pushrods i would see which pushrod felt springy when pushing on it and i would spray some carb cleaner down the push rod tube. but this all depends on why their ticking. has the lifter colasped and the spring in it got weak? or is the hole plugged not letting oil in? or is the lifter sticking in the bore ? ideas?

 

Another old timey method is to add a quart of ATF to the crankcase a day or so before an oil change. Drive as usual until changing oil, repeat if necessary.

 

My Granddad used 2 quarts of kerosene added to the oil, idling for 20 minutes, then drain. You wouldn't believe the crap that came out!