Solved the Miata's problem...

Did a compression test again and found 0 in cylinder 2. So I popped off the valve cover and found this:

That would be the rear intake valve and both exhaust valves on cylinder #2. Looks like collapsed lifters. I can push the lifters down more easily and the springs pop them right back up, but not all the way to the cam.

So maybe just 16 new lifters and it's fixed? No metal bits in the head or the oil (I have a magnetic plug from FM) and compression was 185 on all 4 before the ticking became permanent knocking. I imagine the odd knock I was getting now and then was one or more of these collapsing for a rotation or two before pumping back up.

hopefully that is all it is.

Might be able to get away with just new lifters for the dead ones

If 3 are dead, it's only a matter of time before the other 13 fail. I'm debating whether or not to fix it though.

There's that saying, "Well, while you're at it...." is most appropriate at this juncture, given what you've told us in the past.

I did the cleaning according to the link above with "great success." Before the work, the lifters would clatter a LOT, off and on, throughout the drive. Now I get a few seconds of noise from one lifter on cold mornings, and that's it. These are lifters with about 150K miles.

Mine already have 163K, but what the hey, it's only time and some oil right?

In the old days we would just give it the "Bardahl" treatment.

If the lifters won't return and touch the cam, why is there no compression?

Sounds like stuck or bent valves to me.

In reply to Zomby Woof:

Because the intake valves won't open. No incoming air, so nothing to compress.

In reply to Cone_Junky:

One intake is maybe opening (or at least the lifter's making contact), and I'd expect to see some compression from just the air sitting in there at atmospheric, no? It's still getting squished at whatever-the-CR-is-on-a-Miata...

Can't make compression with 3 valves stuck open

The car is long sold (and fixed) BTW.

Didn't even notice the date. So what was the problem?

In reply to Zomby Woof:

See the pics? 3 collapsed lifters, stuck the valves open. Apparently the new owner pulled them all out and rebuilt them, engine was okay.

Keith says new ones are cheaper now, not that hard to do, but you do have to pull the timing belt and cams.

I've never seen a collapsed lifter hold a valve open.

I managed it in my Locost engine. Too much time with an 8000 rpm redline and stock valve springs. And I have a Miata in my garage right now that I suspect has the exact same problem.

That doesn't bring up stuck lifters, Just maybe bent valves.

Zomby Woof wrote: I've never seen a collapsed lifter hold a valve open.

Ditto...I don't understand how the lifter being collapsed would prevent the valve from closing. I could see a collapsed lifter not pushing the valve open (or opening very little) but then you'll see your compression tester fluctuate between vacuum/low pressure and higher pressure as you crank the engine (if you release the check valve).

Bryce

Maybe you could measure the lash that you have. Then you can pull the lifters out, and lay a weld bead down that's just a little thicker than the lash you measured. then you can file the weld smooth and to dimension.
See how smart I are?

In my case, I jammed the lifter in the head when it collapsed. Or more accurately, BS Levy did Not a bent valve, although I did replace it.