63 Valiant: out of nowhere, my car suddenly wont crank/start. I get a weird noise , kinda like grinding coming from the engine bay (starter) but no cranking...
I'm at a loss. The car has a new starter, a new relay (solenoid?) and a fully charged battery. There are 12 volts going to the main terminal of the battery. anyone have any thoughts?

The pics show the wiring, which I did not change from when the starter worked normally (although the two leads going to the starter are temporarily disconnected in the pic)

Could be the starter is turning, but not fully engaging the ring gear. That would make a grinding sound. See if you can rotate the engine by hand (not using the starter) about 1/4 turn, then try the starter. If the engine cranks, now, the ring gear probably has some bad teeth. It is also possible the starter is defective. I am assuming you have a good ground connection, and positive connection, getting a full 12 volts to both wires on the solenoid.
EDIT: When checking for 12 volts at the starter the wires need to be connected to the starter. It is necessary to put a load on the circuit.
PS, Why did you change those parts?

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 225 nitrous
64 Valiant Signet
64 Valiant 4dr 170

I changed out the both the starter and the relay (terminology wise, is it a relay or a solenoid, or both)? to try to find/eliminate the source of the problem.. The new parts made no difference
I'm getting 12 volts at the starter (large terminal), but nothing from the smaller wire/connection. Also, I forgot to mention, the red light (oil pressure) looks weak and fades out a little when I turn the ignition key. Would a bad ignition switch cause my problem? Grasping at straws here.

The dingus on the firewall is a relay. Just to double-check that it's the correct one, this car has a manual transmission, yes?

Diagnosis here begins with the starter and works backward from there. Go under the hood with a screwdriver and bridge the two terminals on the starter. Does it crank? The starter's not the problem. Go to the starter relay and bridge its two big terminals. Does it crank? The wiring from the relay to the starter's not the problem. Run a test wire from battery positive to the small (1/4" push-on blade) terminal on the relay. Does it crank? The relay's not the problem. Remove the test wire and connect it from the relay body to battery negative, then turn the key. Does it crank? If so, the relay is not grounding properly on the firewall. If it doesn't crank, the problem is in the ignition switch or the wiring from the ignition switch to the starter relay (including the bulkhead disconnect).

All of this is "under" what Charrlie pointed out: if the starter motor runs but doesn't engage the engine, it's a faulty starter or a faulty Rudolph the Red-Nosed Ring Gear. But if the new starter (I see at least one problem with it) and relay were installed in an effort to solve this problem which also existed with the previous relay and starter, you're likely to find the problem with the diagnostic chain I've described.

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

Thanks to u both for such a thorough explanation and troubleshooting guide. Hopefully, now I will be able to isolate the problem. (although it would be helpful to know what Problems you refer to with the starter in the pics)

No sealant between the brush plate and the pinion housing. That's setting this starter up for water ingress and resultant mayhem. The very first starters of this type, early in 1962-model production, came through with no such sealant, and problems quickly developed. A TSB was issued for field-sealing the early-build starters, and production-line starters were sealed from the factory. For 1970 the brush plate and pinion housing were redesigned to use a thick rubber gasket and two external fastening screws, so no more need for sealant. Because the '70-up starter fits and works on '62-'69 cars, most of the "remanufacturing" outfits stopped handling the old-type starter long ago, and it's been very unusual for many years to be able to buy one. Where did you get this starter?

Anyhow, it's an easy fix. Use a good brand of RTV silicone. You'll find the area to be sealed depicted on pages 12 and 13 of this small stack of TSBs.

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

The starter i removed (which may be still good After all) has the word Chrysler stamped on it. The "new" one is a AC Delco remanufactured one I bought on -line.

They all have Chrysler stamped in the motor field frame (the big round part made of steel).

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

Thanks for all the help: I pulled the ignition switch which looked pretty bad.. managed to put a new one in and she started right up.