I have been cleaning a new to me engine to put in my '73. It's a '76 2.0 D-jet- stock valve train. After re-installing the rocker arms I went around and adjusted the valves using Cap'n Krusties' Rocking method and it seemed to be going fine. After getting all valves done I decided to check them all again. This is where it gets weird. While checking one rocker/valve I notice that another one seems to be looser than it was when I set it. I understand how it could get tighter as the cam rotates and closes the valve.
According to the rocking method the Rocker being adjusted is on the backside of the cam (opposite the lobe) and therefor as loose as it should get.

So, why Can I measure a greater gap when It should only be able to get smaller?
Apparently I'm not the only one who has run into this.

Also, I get different gap readings when using the piston at TDC method. Some are the same, some loose or tight.

This is my first time working on the rockers/valves, FWIW.
Let the learning begin(continue)!

Bob, by your description it sounds like engine is out, on a stand, etc. Is the flywheel on, or has it been removed? If your flywheel is off, the crank can shift position slightly along the axis - affecting valve adjustment.

Yes engine is out, but FlyWheel is still on.
??

In my case:

Engine still out of the car, with the transmission still on it. Valves adjusted at TDC, according to the mark on the flywheel. Re-checked valves using the opposite-rocking method. Any valve whose counterpart on the same cylinder was open had greater clearance than was set at TDC.

I never could get an answer as to why that might be. The only thing I could think of was that the rocker shaft was moving. But I did torque it down to the correct spec, 10 lb-ft.

I'm waiting to hear any good answers as well!

--DD

Worn out cam bearings? The rocker shaft is not the only thing that can move...

That's why we pulled the drive train from my wife's car. I kept adjusting but got different clearances after a full revolution. I'm guessing the cam bearings are worn - we'll find out for sure when we tear it down.

It did that with less than 10K miles on a fresh build.

--DD

Check the through bolts torque. Maybe you're lucky and it's not the cam.

I had the same exact issue with my previous engine. After tearing apart that engine, I found a worn cam with flats everywhere. After installing a new cam, all that weirdness went away. I would think a descent temp repair for the meantime, installing hydraulic lifters, till you can tear down your engine?
I found it extremely helpful watching the Jake Raby bug me not movie. The video is free on the pirate bay site.

Well meaning advice, but. . . doing so is a disaster in the making. Putting a fresh set of lifters onto a worn cam, is about the fastest way to remove those little, but necessary bumps that open the valves, at the same time introducing tons of metal into your motor. Adding hydraulic lifters to a worn-out solid lifter cam will only accelerate the cam's destruction. For your motor's sake, DO NOT DO THAT

It's easy to pull a push rod tube, slide a lifter out and inspect the cam. If you pull the motor, you can also remove the oil pump so you can inspect the cam gear rivets which can get loose and cause the cam gear to move side-to-side and cause all kinds of cam/lifter/valve adjustment issues.

I must say I don't like the direction this is going!
I'll be pulling the rockers and tubes again. Then pull lifters and see if I can inspect the cam a little bit.

Would it be possible to check for fore/aft motion of the cam through the lifter hole, or must the oil pump come off? I doubt you could measure but maybe get an idea if there is slop.