Howdy Back Trashline:
Before you jump into replacing the lifters, take a closer look to determine the cause. It could be the lifters are sticking as a result of internal varnish build up due to poor maintainance. If that's the case try one of the miracle oil additives on the market. They are nothing more than a high concentration of detergent in the oil, but they do work in some cases. Changing the oil and filter regulary will help maintain it. In the early 50 it was fairly common practice to add a quart of diesel oil to a Chevy six to quiet it down. I would not recommend that in your case.
If that doesn't do it consider taking off the valve cover and check the tightness of each rocker by manually rocking it back and forth. There should be no clearance in a hydraulic lifter engine. If there is clearance, check the oil delivery by starting the engine and watching to see that oil is getting to the front cylinders. It is no unlikely for the shaft and/or rockers to get plugged up. Once plugged and no oil gets to the rocker arm the contact between the rocker and the pushrod ball wears very quickly, leaving a ridge or point on the ball end of the pushrod. The remedy is to remove, disassemble and thoroughly clean the shaft and the rockers- inside and out. If wear is visable on the ball end of the pushrods they will have to be replaced. This would be a wonderful time to consider adjustible rocker arms. Each rocker has two oil supply holes to the shaft, On at 11:00 and another at 3:00 when viewed from the front. Make sure they are open and clean.
If neither of the above seem to be the problem, consider cam lobe wear. If your engine has lots of miles and wear, this is a possibility. Changing the lifters will not solve this.
Finally, to replace the lifters the head must be removed to gain access to the lifters through the top of the block. Since the head is off you might as well spring for a valve job and include milling the head.060". .030" will compensate for the difference in thickness of the new head gasket, and the other .030" will tighten the valve train clearances. You won't mind the extra compression either.
Caution! New lifters on an old cam is risky business. If you don't already have lobe wear, you likely will.
So, you might as well rebuild the whole engine while you're changing lifters.
Enjoy the journey.
Adios, David
