Zed Head

... mistaken identity Does this not look like Z? But it's off. Not sure what it actually is. 1:17.

When you say rotor do you mean hub? It's attached to the disc but many people think of the rotor as the disc itself. You can buy things called "rotors" that have no hub attached. Just a brake disc that fits over wheel studs. I don't know how they ended up being called rotors. A picture would be good, even one from the FSM. I know that they early 240Z hubs are different from later hubs. Scalloped versus round if I remember right. Not sure about dimensions or caliper fitment.

Grease the rear driveshafts' u-joints. The propeller shaft u-joints might have Zerk holes also. You might need to get a Zerk fitting since Nissan plugged the holes with screws from the factory. The ball joints need grease also.

Looks okay in that picture. As said before, check all of them. If you want to get a better idea, mark all of the wear pads with some layout fluid or a magic marker then rotate the engine a few times. The cam will rub away the marking and show you what's happening. Some of the wear might be from before the new camshaft was installed. Good luck.

This angle of the one that you think is off-center.

That's not good. Can you get a shot from the side to see if it's up on top of the edge of the lash pad. Might be that you actually have a very loose rocker arm. The end of the rocker arm should sit between the two ears. Can't tell which one you're looking at.

A cam lobe that's dropping off of the edge of the wear pad could be the cause of the noise you're hearing. The pattern is definitely "wrong", out of spec., but as RacerX said some people do it on purpose to gain a bit more valve lift. Overall though, the odds seem good that you'd be better off with the proper lash pads to get the wear pattern centered. The three that you showed seem very close, the middle one might even be the noisemaker.

Take the same picture from the other side. Compare to RacerX's pictures.

You can see the wear pad without removing the rocker arm. It's more difficult but a bright light and holding your head in the right place makes it possible. They're facing up, right there under the cam lobes. Worth taking a look before you get too deep in to things. Actually you were looking at them when you were measuring valve lash.

You might take a close look at the wear pattern on the rocker arm pads. Kind of sounds like valve train noise on one or two cam lobes. Just a guess. With an aftermarket cam the right lash pads might not have been used. Definitely sounds like it needs fixing. The engine sounds pretty good overall but the noise is bad.

Reptoid showed how a normal timing tab and damper pulley work together in post #11. You have to be able to eyeball where the mark is when your timing light flashes. Unless you put up a new video nobody knows what the actual noise is that you're hearing when the engine is running. Your video was the wrench on the camshaft sprocket. Here's Reptoid's picture and yours. All I'm saying is know what you're working with. We're at post #42 and there's still no reliable way to check ignition or cam timing. Engines are all about timing.

I'd spend some time figuring out what you have and what shape it's in. Get the numbers of the cam, find TDC, get a proper set of timing marks installed, set your distributor correctly to TDC, measure cylinder pressures to see if they're all balanced, etc. Kind of seems like you just bought this Z with a modified engine and started driving it. How did the PO set up MS if he couldn't even use a timing light to see the timing? Your "doofer" is miles away from the damper. (p.s. apparently doofer is British for doohickey). Here's some stuff on what you probably have under the distributor cap. https://www.diyautotune.com/product/54-mm-optical-trigger-wheel-for-nissan-l28et-or-vg30e/#tab-ywtm_78211 https://www.diyautotune.com/support/tech/hardware/nissan-trigger-disc/

Map location says Salt Lake. He says he's from Houston. 1st post. "experience about the Z"? Odd grammar. Hallmarks...beware.

But how do you know? Maybe it was for both. Or either. Or an unintended benefit.

I wonder if Nissan was changing the shape of the curve to get more charge time with the ZX reluctor setup. Also still wondering about the ZX turbo ignitor swap with the GM HEI module. The 5 volt reference never goes negative. Anyway, neat stuff. Different from the usual. Here's your other post with the ZX wave form. Post #261.

Yes, if you have a loose pulley removing the belt should remove that as the possible cause of the noise. But, the downside is you'll have to loosen the alternator adjustment, which can be difficult if you haven't done much engine work. You're in that danger zone of learning as you go. You're probably going to break some things. Really, I wonder now about your lash adjustment if you don't know what a fan belt is. Again, no offense intended. Find those youtube videos and watch many. Have you looked at your ignition timing on Megasquirt software?

Nothing wrong with not knowing but you really shouldn't double-down on the wrongness. It puts people off. No offense. So the turbo distributor is what you'd expect for a Megasquirt application. If the guy set it up correctly you might be able to find zero through the Megasquirt program. But, you won't really be confident in it. Anyway, sounds like it runs but has a noise. Try running it without the fan belt on and see if the noise goes away. It won't hurt it for a short while, especially if the engine is cold.

The doofer is the timing tab with the serrated edge. And, my comment about pulley size might be more important than it seems if you're planning to use this as a daily driver. The Z's are known for having low charging current at idle speed. A smaller pulley makes that problem even worse. One thing at a time though. On the Megasquirt question I'd guess that it's being used for ignition control only. It's possible. Have you looked under your distributor cap? There might be other odd things on that engine.

It's because you said this earlier.

Just realized that that is a 280ZX timing mark tab. You never said what you're working on, you just kind of jumped in to valve lash ash and noises and have "280" in your user name. Looks like a 280ZX engine. Anyway that's an aftermarket damper with odd markings. Might be a Powerforce Performance Professional Products "Harmonic Damper" like the one MSA sells. You have some mysteries ahead of you. Who knows what's in there. Read the notes about the timing marks. Might as well just start from scratch with RacerX's advice. p.s. you always need a damper. Somebody just replaced your factory damper with aftermarket. But you could go back to a stock ZX damper if you wanted to make life easier. Seems like the pulley diameter is smaller with that "performance" unit which will make your alternator and water pump spin slower. Both bad for 280ZX and 280ZX engines. https://www.thezstore.com/product/5074/performance-harmonic-damper-70-83-zzx

Can you take another picture and pan out to include the timing tab on the left.? Never seen that many points. You need to decide which one you want to use as zero. Grab on to that damper (an engineering/physics word, not dampener) and yank it around and back and forth. See if it's loose. It's been known the that the wrong combination of bolt and washer can leaver the damper loose on the crankshaft. Plus the PO replaced it for a reason, there might be damage under there. That bolt head looks pretty beat up.

In the States the 280ZX changed ratios in 1980. According to the FSM's. 1979 had the older wide ratio 5 speeds, 1980 had the new close ratio. 1980 also had the odd 0.773 overdrive (although I got one from a 1981 car, not sure how it got in there). So a generic "280ZX" remark can be confusing. If you want to see something wild check out all of the differential ratios and vehicle combos for 1979. They kind of went nuts. I've never seen a 3.7 long nose R200 but according to the book they were available. Even the 3.364 R180 is out there, supposedly. And, the 4 speed is still shown.

If the valves are sitting proud of the seats they can warp. AKA burn. It is odd what you're seeing. Might be interesting to take a measurement on 3, put the plug back in, start it and rev it and measure again. If your carbon theory is correct you'd think it would blow off and you'd get a different number.

Maybe you have some sticking valves. Be ready for a rocker arm to pop off.

Sometimes an exhaust leak can sound mechanical. Nissan actually provided a way to monitor chain wear. The notch and groove. Some aftermarket sprockets don't have the notch though.