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Recently adjusted my lifters on the 261 in my 1942 dump. I did them while running,(tighting a few turns then lock them down)to quiet them down, now I'm reading a "noisy lifter is a happy lifter". I feel that not knowing the condition of the camshaft, setting with feeler gauge would be useless.The truck is not on the road yet,and runs great in the driveway. Will running condition change with a load on her from street driving? Can i do damage to the pushrods?. When running with valve cover off, I can see the pushrods are rotating. Can I feel confident that no damage will occur?

A noisy lifter is a disaster waiting to happen. It's like repeatedly smacking the top of the valve stem with a hammer. You'll experience mushrooming of the top of the valve stem, and increased wear at the tip of the rocker arm.

A camshaft lobe has a short area of slow lift called an "acceleration ramp" which allows the clearance between the lifter, pushrod, rocker arm, and valve stem to be taken up gradually before the quick lift of the valve begins. It just happens that the height of the acceleration ramp is equal to the clearance the manufacturer specifies. If any clearance is added to the factory spec, the speed of movement is increased after the ramp height is taken up, resulting in hammering of the parts instead of a smooth valve lift.

Make 'em noisy if you want, but if you do, you're destroying the valve train. Better use the right hot adjustment specifications!

A running adjustment is a total waste of time. The 261 is supposed to have a mechanical lifter cam, and the idea that adjusting the noise away is a proper adjustment procedure is an incorrect assumption where hydraulic lifters are concerned. Stop each cylinder on TDC compression by using the companion cylinder adjustment method AFTER running the engine at least 30 minutes to get it up to normal operating temperature and use a feeler gauge to get an exact clearance on every valve. If it's noisy after that, install a new cam and lifters.
Jerry

What do you mean by this statement? If someone has put hydraulic lifters in your 261 then you could tighten a few turns (although 1 1/2 turns is recommended) after the push rod slack is removed.
With solids you would use a feeler gauge.
With solids if still noisy after adjustment you may need to reface the valve end of the rocker. They wear where they contact the valve. If worn a feeler gauge bridges this wear while adjusting and will give you a false reading.

Did all the truck 261s use solid lifters? Our 1960 Canadian Pontiac had hydraulic lifters.

I loosen the locking nut and turn the screw alittle on the rocker arm.

Yes, the USA truck 261's used a solid lifter cam with the same timing and lift as the one used in the Corvette 235's.
Jerry

Post the engine serial number on the pad/ledge on the block that is just to the rear of where the distributor goes into the block. This will assure you/us that you have a truck engine (all of which came from the factory with mechanical lifters). A 58-63 truck engine could have been later fitted with hydraulic lifters.

In case the posts above are not clear, your adjustment technique is not the recommended technique for mechanical lifters

HrL describes the accepted/recommended technique. A few techniques are described in the Engine secton of the Tech Tips on this webite (look for the Tech Tips link at the top of this page). Here is a description of an adjustment technique.

The pad behind distributor is blank,or heavy paint. The motor is pretty clean so i did not want to scrape and leave uncoated, The other numbers are 848850 on pass side head,3836850 on drivers side. I actually used your 1954 a-d.com site to run the #s and they all point to a 261 1960-62?. Will use your posted recommendation for adjustment this weekend possible. Thanks for everyone's help