Good...
...not as good.
That's not it -- but there could be an external air leak into the engine (valve cover gasket, oil pan gasket, oil dipstick tube...).
Blowby. This is probably what's going on, I'm afraid. Good idea to do a leakdown test, which will do a better job than a compression test at describing the engine's condition.
To be expected with everything what you've described (lots of short trips, blowby, etc)
That's the easy and quick way to do it, or pull the distributor, turn it upside down, adjust the position of the hold-down plate, and reinstall the distributor.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

I decided to replace the brittle rubber grommets for the PCV valve and the crankcase breather. After I removed the old ones I could see a thick layer of gritty black crud on the inside of the valve cover and baffle. I don't know if it's enough to restrict air flow out the PCV valve but it can't be good. Can I clean this out with kerosene or trans fluid as people do? Or should I remove the valve cover and clean it some other way?

Here's the sludge I could get out just by sweeping my finger inside the openings for the PCV valve and the breather. It's probably about 2-3 tablespoons.

Oh, and by the way don't buy those gloves. They rip if you touch anything.

Harbor Freight 9 mil XHD gloves are best for working on things that you may need to have contact with and keep the glove integrity on anything but sharp edges....

I think I'd take the time to pull the valve cover, clean the inside surfaces and baffle passages....you may also find some lingering curd on your rockers, etc....

Shopvac as you go so chunks don't migrate.

......and then we move on to Valve Adjustment.

_________________
Yeah....Im the one who destroyed this rare, vintage automobile.....

Yes remove valve cover, clean it with what ever you have that cuts coked on oil then turn your attention cleaning rocker arms, rocker shaft etc. being careful not to allow any of the hard carbon deposits drop down into the lifter galley.

A more efficient method probably would be to remove loaded rocker shaft from head, and clean it on the bench. While it is removed cleaning of head will be much easier. Pull push rods keeping them numbered and in order by sticking them into a chunk of cardboard pierced with 12 holes. They will want to go back into the same hole.

Once rockers on shaft and push rods are removed labeled and stored, plug off or seal the various openings to lifter galley so none of the crud removed during cleaning process drops down in there.

Rocker shaft may or may not have to be striped of rockers, spacers and springs, for cleaning. If you decide to strip shaft of rockers string each rocker & spacer in order of removal along with spacers, as spacers are of different sizes depending on their position, onto a length of wire. I use a chunk or Romex for this procedure, and one by one make sure the oil passages of each rocker is open. Flush with brake cleaner, carb cleaner, or even EGR cleaner one at a time. Then flush out the rocker shaft. Make notes and or photos showing how all these parts were orientated at time of disassembly including oil hole in shaft and which end points to front of engine so it all goes back together as found.

Very important detail:
A special skinny bolt is used to attach the firewall end of rocker shaft to head that allows motor oil to be pumped from sump up into rocker shaft. Use the wrong bolt and no oil gets up top.

This project will improve top end oiling, circulation of clean free flowing detergent oil will clean up lifter galley over several oil changes.

One more thing:
When unbolting rocker shaft from head back off each bolt a few turns at a time to keep from deforming the shaft. There is a lot of pressure exerted on this shaft by the valve springs pushing against the rocker arms. Same procedure when installing it. Start tightening sequence in center of shaft tighten down a few turns then move to next bolt to front, and jump back to next bolt from center to rear of engine just like torquing down a head. Start at center work symmetrically to each end of head in several steps being careful not to bend the shaft. Be sure while tightening shaft down each push rod is centered in its respective rocker. It will all go back together nicely, and that recheck lash adjustment.

Torque spec for rocker shaft "hold down" (or bracket) bolts is: 25 foot-pounds.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Good idea.
It's not, but it is symptomatic of an engine that's very dirty inside. Causes include the PCV system not working, lots of short-trip driving where the engine never warms up properly, and/or blowby.
If you want to quickly make a reason why you need a new engine, sure.
Yes. Not least because your engine is probably long overdue for a valve adjustment.

As for cleanup: you're going to find the inside of the valve cover is thoroughly encrusted. Rocker shaft assembly, too. Here's one way to take care of this:

Find a machine shop that has what is called a "hot tank". This is a big tank (gee...) filled with a caustic solution. Parts go in dirty and come out clean. No aluminum or other light metal you ever want to see again can go into the tank—only iron, steel, copper, brass and bronze. Remove your engine's rocker shaft, keeping track of the special rear bolt, get a piece of steel wire (I've used an unbent wire coat hanger) and string all the rockers and spacers onto the wire, then twist the wire closed so you have a loop. Take that and the shaft itself (as well as perhaps your valve cover and other stuff you want really clean down to bare metal) in for hot tanking. Direct the machine shop to remove the end plugs from the rocker shaft (or do that yourself) and then replace them with new plugs once the shaft is internally clean.

Once you get the cleaned parts back, remove each rocker arm's adjusting
screw, taking note of how easy/hard it is—any that are easy to turn will
need to be replaced or reworked so they're difficult—and chase the rockers' internal passages with spray carb cleaner and a suitably-sized wire.

If you can't or won't go to a hot tank, then bring the hot tank to yourself in the form of oven cleaner. Ordinary Easy Off, not the "fume free" type. This is sodium hydroxide (lye), so wear sturdy gloves and a face shield and use it only with plenty of ventilation because it is painful and injurious to breathe even small amounts of the stuff. It will strip grease, oil, sludge, crud, paint, old gaskets, etc. "Rinse" with carburetor or brake cleaner or (more economical to buy by the gallon) denatured alcohol.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks everyone for the detailed replies. I have actually adjusted the valves about a year ago (I thought it ran worse after, so I adjusted them twice more checking for the easy slide fit according to Dan's valve adjustment instructions). While I had the valve cover off I wiped it down but of course I couldn't get my rag into the baffles. The rocker assembly was not too full of crud--some bits and pieces here and there but not a lot. Also, I could see each shaft was spitting out oil. Of course it may have gotten worse since then, especially since I apparently went way too long between oil changes.

I really appreciate the detailed instructions on cleaning the top of the engine. I might tackle that next week. In the mean time, here's a video of the airflow in and out of the crankcase breather with the new PCV valve and grommet. Air blows out at high RPM but there is some suction at idle.

If so, they didn't get adjusted correctly. :-\
Is this a change from how it behaved before the new valve and grommet?

(Also, yeah, it does sound like your valves could do with an adjustment)

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

I didn't look at the airflow out of the crankcase breather before I first adjusted the valves, so I don't know if that had any effect. But I suspect not, because I have had fuelly oil in my air filter since before that valve adjustment.

I think I recall tightening each valve a full turn or more to get to the 0.010" and 0.020" measurements. The first time, I adjusted so that the feeler gauges were grabbed pretty hard but could still slide. The second and third times, I went for a looser "slide fit" so that I could still feel the gauge being grabbed, but only lightly. Of course with the engine running, the gauges are covered in oil, so it's hard to feel how tight the grab is. Do I want to adjust so that the feeler gauges are not grabbed at all? If so, that would probably take things back closer to the adjustment before I messed with it.

If you can hear bad valve adjustment in the video, can you diagnose what the correction might be?

This is the kind of practical and useful information that keeps me coming back to this site. Thanks again, Dan!

_________________
Casually looking for a Clifford hyperpak intake for cheap.

Sorry, I misread your question. No, I don't think it's a change from before the new valve and grommet.

I should have mentioned: the first rinse after soaking with oven cleaner should be water. Preferably very hot water. Then chase that with brake cleaner, carb cleaner, or denatured alcohol.

The key to a good valve adjustment is understanding that the gauge is going to be grabbed when the valve is open; what you're adjusting is the clearance when the valve is closed (gauge not grabbed).

I'd proceed with the cleanup (including air cleaner + new filter), oil change, valve adjustment, and "Italian tune-up", then see where you're at.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

I see I got confused about what is happening during the valve adjustment, but now that you remind me, I do understand that the gauge is grabbed and released, grabbed and released, and you are checking the clearance during the release part of the cycle. At the time, I felt like the gauge was sliding pretty freely but maybe I just need to back off a bit more.

You want there to be some perceptible drag during the "release" part of the cycle, but not so much that you have to tug on the gauge to get it out. "Slides freely" is too loose.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.