The Stovebolt Site Forums The Shop Area Engine Shop Valve Clearance

Hi Folks,
Spring is almost here and I'm planning my first road trip with my 55 series ll.
Thought I'd check the rocker arms and valve clearances. The last adjustment was done by a friend and I'm not sure he did it correctly.
As I haven't adjusted the valves on a any stovebolt in something like 50 years, or so, I thought I'd do a dry run to be sure everything under the valve cover is OK.
No sooner had the cover off and I found something that confuses me. Lined up the timing mark, had the rotor pointing to #1, and it appears that both #1 intake and exhaust valves were closed. The motor was cold but there was no valve play anywhere! Shouldn't some of the valves show some play?
When warmed up, compression is excellent and equal on all cylinders HOWEVER, the engine "Rattles" above 2500RPM and when I start it ice cold it also has what seems like a bearing knock until the oil pressure is up. Now I am wondering if the valves are too tight and if that could be the reason for the noise when warm above 2500RPM.
Oil pressure is very good when warm and it starts right up now that I changed the battery. Did a load test on the old "new" battery and it collapsed almost immediately down to less than 6 Volts. That was the reason for my hard starting problem.
Will reset the timing and install new plug wires after I get the valves sorted out. I want to eliminate possible pre ignition problems.
If any one has some suggestions - I sure could use a few comments to settle my confusion.
Many Thanks

By closed, do you mean no rocker movement (that would be open valves), or are both rockers moving (valves would be closed against the head, and ready to fire)

The timing mark is lined up to the pointer two times for every rotation through the firing order. Rotate the engine/crankshaft one full revolution and both #1 valves will be closed (loose rocker arms and that is when adjustments can be made (if you use the static method of valve-lash adjustment).

Is it possible the engine has hydraulic lifters? If there's been an engine swap from a Powerglide-equipped car sometime in the past, you could have a hydraulic-lifter engine. If so, there will be no gap at the rocker arm, even at TDC on the compression stroke. The rattle you're hearing on startup could be collapsed hydraulics pumping up.

Try this- - - -warm up the engine, then pull the valve cover and line up the timing mark and distributor rotor the same way you did before, them use a long screwdriver or a pry bar and put a firm pressure against the pushrod side of one of the #1 rocker arms for a couple of minutes. If you've got hydraulic lifters the gap at the valve stem will increase to about 1/8" or so. As soon as the engine starts the lifter will refill.
Jerry

It would be a pretty hard to have good compression and smooth running engine with the valves adjusted wrong. I too suspect hydraulic lifters. If you rotate the engine to #1 TDC and both rockers have zero lash, rotate one more turn back to TDC, if they are still at zero lash you have hydraulic lifters, other wise you would have low compression and/or back fire up through the carb and out the tail pipe.

To adjust a hydraulic lifter, go back to compression stroke on #1 cylinder, TDC, its easy to find if you just watch the rocker movement. When the intake rocker just closes, the timing mark should be getting close to alignment and the piston should be almost to the top of the bore. Once you get to this point, back off the adjusting screw till you can rotate the pushrod with your fingers. Slowly tighten down till you get to zero lash, then give it a 3/4 turn down. This will put you in the middle of the lifters range of travel. You can do both rockers at this time. I like to do each cylinder then rotate the engine till the next two valves are closed. It's just the way I like to adjust valves.

If the valves are adjusted with only zero lash and not the added 3/4 turn, you can have lifter rattle when cold, and it might explain the rattle at higher rpm as well. If you find after checking the for solid lifters the way Jerry spoke of, that you in fact do have solid lifters, then adjust them as needed using feeler gauges. You should be able to squeeze the oil out of a hydraulic lifter in a fairly short amount of time with a long pry tool.

Joe

Thanks for all the suggestions! For clarity sake, I did the pry bar test and they are definately solid lifters.
I'll take it for a 30 minute drive tomorrow to be sure everything is warmed up and then do the valve adjustment as per the service manual.
Engine is original to the truck and has 78,000 miles on it.
When I turn the engine over by hand all the valves open and close but there is no apparent free play anywhere.
My gut feeling is that the valves are just too tight.
I think my friend who adjusted them may have assumed they are hydraulic and that's why they are too tight. Sure am glad he didn't add the 3/4 turn. At least it seems that way otherwise I wouldn't have such good compression (150#'s on all 6 cylinders).
Unfortunately, I can't reach him he's away on a lengthy trip and won't be back til the end of April.
Thanks again. I'll get back to you all when I have more info.

Sam