Classic/Antique Car Repair: 1947-1949 Packard Super 8 Engine, hydraulic lifters, shop tomorrow

Question
Hi Dick
I would like to know what the correct procedure is for setting the valves.  The engine has hydraulic lifters and the problem that we are experiencing, is that the engine will lose compression after it runs a bit on a couple of cylinders.  If the engine sits a while, the compression will be fine on those two cylinders.  The lifters have been rebuilt, camshaft redone and I am wondering what the pre-load should be in relationship to the valve stem to the lifter.  6 cylinders have 120 pounds, number 7 cylinder shows 90 pounds, number 1 cylinder shows 70 pounds.  If engine sits a little while all cylinders show 120 pounds.  Engine appears as though the lifters are pumping up and holding those valves off the seat.   

I would like to know the correct procedure to adjust it.

Thanks

Answer
Yes, you may be right about what is happening, although there is another possibility.

Regarding setting the valves, there is a specified clearance for each valve with the lifter collapsed - the way to set this is to take a spare lifter and remove the internal check valve so that it will collapse all the way and stay that way, then measure the clearance between the end of each valve stem and the top of the collapsed lifter.  As I recall, that spec is 0.030" min, 0.070" max, but I will have to check that and correct myself if I am wrong.  I will post a follow-up to you with a revision if I am wrong, when I get to my shop tomorrow, where I can look up the numbers.  To adjust the clearance, you have to grind material off the end of the valve stems, of course.  This has to be done carefully, so that the stem is perfectly flat when it is done.  This problem develops because the grinding of the valves and seats brings the stems down, especially if the valves are used valves.

The other possibility, which gives the same symptoms, is that the valve guides are too tight - and this is actually more common than the first problem - people tend to set them way too tight.  Make sure you have 0.002" clearance on the intakes, and 0.004" on the exhaust valve stems.  The clearance tightens as the engine warms up, giving the symptom you describe.

Let me know if this works for you.  If you don't hear from me, the specs I gave you from memory are OK.

Dick