Howdy Zachalak:
Your engine is suffering from sticking hydraulic valve lifters. This is not an uncommon occurance for our engines in high mileage/low maintainance conditions. Your engine does not have an adjustable rockers so adjusting the stock rockers is not an option. So you have a couple of options;
1st- Try a high detergent oil additive. This is a "Maybe" solution. The idea is the the high detergent quality of the additive will desolve the crud and varnish that is causing the lifter to stick. In addition you will want to change you oil and filter religiously every 3,000 miles of less. In the old days, we used to add a quart of kerosene, as an internal engine flush. I'd not reccommend that today as the shelves at the parts store are full of pour in products that are more effective and safer. This is the cheaper/easier solution, but it may not work, depending how dirty/old/worn your engine is. But it is worth trying 1st.
2nd- Your lifters may be so stuck inside that they are functioning as a solid lifter. You can add an adjustment by finding an adjustible rocker assembly from a pre-65 144, 170, or 200. Get the rocker arm assemble and the pushrods. It is a simple remove the rocker cover, remove the 4 bolts the hold the stands in place. Note that the rear most stand must be at the rear of the head or you won't get oil to flow through the shaft. the rear bolt will alos be fluted, or tapers to allow oil to flow past. It is always a good idea to dissassemble and clean the old rocker arm shaft, rockers and stanchions.
New adjustible rocker and pushrods are available. I don't have the source handy at the moment.
Now you can adjust the valves as you would a solid lifter engine.
3rd- Rebuild and replace the worn rockers, cam and timing gear. You might as well do a whole engine rebuild at this point.
Hope this helps you.
Adios, David
