white89gt

For an experiment, you really ought to try and pull the PCV valve out and see if it changes at all.

pnolans

It starts, and momentarily knocks when I start it. Then quiets down at idle. When I rev up to 1500 it starts again. Gets really loud from there.

The problem is, I have to leave this place where I'm staying, and leave it here until next time I'm up here (CO) . I'll be back in Sept ... to do some "farm-sitting" for my friends.
The truck is parked here.

Thanks so much for the help,

Pat

River1

There's often but not always a whistling or whining noise that goes with a PCV knock. Have you ever heard this?

Jbrew

Haha I know...force figured that one out one fine day, long ago lol. Couldn't believe how much it mimics a rod knock though. I heard it for the first time at idle, thought for sure that engine was done. However, the stethoscope lead me right to the valve...sure enough!

OP, -what's normal and with age, these engines can both knock or piston slap at cold idle..it's usually cylinder #1 (piston slap issue only). Perhaps even a tad at warm idle. No big deal and common with the modulars...lot's of life in it yet as long as it's maintenance properly. What's not common is knocking above idle...that's a bad sign imo.

Make absolutely sure it isn't something else, like say confusing a knock with a lash adjuster issue. It's a different sound...but still.