I am getting set to adjust valves on my 1984 D150 (gasket, feeler gauges, etc.).

Are you guys telling me I can't do it?
How am I supposed to quiet down some noisy lifters? HAHA!

I didn't see anything in the factory service manual about adjusting valves, but it didn't dawn on me that they were not designed to be adjusted. Is this true?

Thanks.

1981-1987 slant sixes got the hydraulic lifter set up, so no adjustments (that's done by oil in the lifter and load from the rocker/cam/pushrod on the plunger...
but your truck is older and you never know if someone swapped in another engine, or replaced the setup with the mechanical set up... pulling the rocker cover
and looking for the hex headed adjuster bolts on the rockers will tell you which way it is...

So, there's a chance I won't get to experience hot oil flinging about while the clackety clack tickles me fingers...dang!
I should've bought an even older truck...

Your point is well taken about possible modifications in the last 34 years, thanks.
I will either pull the valve cover or take a look in the filler/breather holes with a good flashlight.
Maybe I can cross *adjust valve lash* off my long list for this truck and move on to the next item.

You really won't need a flashlight, just remove the oil cap. The rocker is right underneath. If there's a cup on the rocker where it meets the pushrod, you've got yourself a hydraulic drivetrain. If there's a nut, you have solid lifters.

If you do have adjustable rockers, there's not a ton of oil that spurts out when you set the lash. Not like other makes/models anyway.

_________________
If it was easy, everybody would be doing it.

Survey Says: Hydraulic

Thanks.