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How terrible do you think it is if I drive it for a couple of 50 mile jaunts over the weekend? It is scheduled to make an appearance about 50 miles away. Even if it is one or two lifters? I have been going through the thought process, and I cannot figure out what might be damaging, excepting maybe the tip of valve stem? If the lifter is bad, well, then it is bad and will need replacing in any case. It starts out o.k. cold and then the ticking starts to appear about 20-40 minutes in, I measure compression and all my cylinders were ~120 psi cold. I replaced a couple of lifters and it made no difference, though I may have replaced the wrong ones or horror of horrors the ones I replaced (which were extras I had from when I replaced them all) may have been bad too! OTOH, it may just be the manifold gasket. I cannot get new manifold gaskets until next week.

Also, on a separate note - how does one effectively torque the manifold? I can get a torque wrench on maybe 3 of the bolts, the rest I just try to "match" the torque I feel on the ones with the torque wrench with my arm and a piece of pipe I slide over the wrench. But some of those bolts are hard to do even that way. I bought a "curved" wrench that fits in there a little nicer, but the lever arm is small so hard to get a lot of torque on that.

I checked my oil pressure and it was 40 psi steady at idle until after about 20 minutes of idling it started to drop a bit, after 40 minutes it was somewhere around 10 or 15 psi, the red light hadn't started to flicker. At idle after an hour of hard use at idle the oil pressure red light will flicker. I haven't installed an oil pressure gage in the car, though the one I have been using is amenable to that, I just was loathe to drill a hole in the firewall and under the dash for one.

I didn't drill a hole in my firewall for the gauge. I just ran the tube through the existing wire grommet. Previous owners had installed something under the dash, so I used one of those holes, and drilled another. You can't see the holes unless you are on your back upside down on the floor.

I personally like having the gauge for peace of mind. It's so far down that you don't even notice it is there and you have to work to look at it. Your oil pressures sound fine, but it is nice to have an instant read.

-Kevin

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Just drive it. At moderate speeds even bad lifters will usually be quiet and the tapping occurs within the lifter so there is no external damage.

I have to place the end of my stethoscope directly on the lifter body to tell which one is tapping. The only other sign is that very bad lifter will spray a shot of oil upward with each stroke.

Thank you Ross and Kevin!

I now realize the best way to diagnose this is with the engine hot, the car up on stands, the right front tire and access cover off, the valve covers off, the engine running, and a stethoscope to my ear. From a 21st century standpoint the idea of running the engine with the valve covers off is, well, not something I really conceived of a as a possibility, but now I understand that's how things are best done.

Will report back, but probably not for a few weeks.