Captain Obvious

The restarting procedure sounds good to me. I made up a little remote starter button that I use. Push button switch with two pigtail wires. One of the pigtails has a female spade that plugs onto the starter solenoid (after disconnecting the original B/W wire) and the other pigtail has a clip that attaches to the battery terminal. Cranking that way (with the rest of the car completely off) produces motion without any of the other ancillary functions like spark or fuel. Fuel pump doesn't run, and the ignition and FI systems don't get power so they sleep through the process. Make sure the car is not in gear. And as for the thing about the OSK timing marks, my mistake. I thought you had said that the OSK did have the marks, but I guess that was the voices in my head. Make sure the car is not in gear. Oh, and make sure the car is not in gear.

Carp. Well at least you caught it before it did something unrecoverable. You must have pretty good ears to have heard that issue so early! Clean room... That's what I need.

Right, it doesn't care. And probably neither will anyone else. I've been in to multi-thousand mile engines recently and the timing marks still looked good. That said, if I get the option, I'd like to have the marks. @Dave WM, I thought you had said earlier that the OSK had the timing marks. Is what you got different than a pic you were shown prior?

Yuck. No fun. I don't get the weld spatter. Anything else you think of that it could be? I mean, I gotta admit that nugget on your valve guide sure looks like a weld spatter bead, but honestly.... How? Really? Still hot enough to stick there down inside on a valve guide? Are you sure it's metal? Is it magnetic? I'm going to build myself a clean room when it comes assembly time.

The Canadian Tool Exchange visited last night!! Thanks @240260280!! And even though I'm jumping the gun, I just had to try out the ring pliers. Seem to work just fine: And speaking of such things... The Ring Fairy made a recent visit as well:

I thought it was "M sub f".

I've been into two later model ZX motors in recent past and they did not have gaskets on the tensioner. I don't know about earlier years. As you mentioned, it could be something they dropped somewhere along the way. So I took a good look at the tensioner and guides from my 83 motor... There were no markings that I could find on the tensioner, but I did find some markings on the guides. tight side side (left). Had a KR inside a circle. Did a little web searching and came up empty: The slack side (left) has a marking from Tsubaki. They are an old Japanese chain company which makes perfect sense: I cannot prove it, but I believe these parts are original from the factory.

I'm no expert on the finer points, but I do not think there was a gasket behind the tensioner when that motor left the factory. I believe the gasket behind the tensioner is an indication that someone had replaced all that stuff in the past. Do you see any manufacturer marks on any of the parts? I'll look the factory stuff over from my F54 tensioner. If anything, I would expect to see either a Nissan mark, or a Hitachi mark on my original stuff. I'll check.

Word.

I've only got one of my pistons here (the rest are out at GGRs), but the one I have here was assembled like the one you pictured above. And I'm confident that the one I have here was NOT one of the two bolts that came out during disassembly. (Point is, I have high confidence that the one I have here is the way it came from the factory.) I don't know if my other five pistons are like the one I have here but I'll let you know when I get a chance.

Although, I'm not convinced that "interchanging rod bolts has the same effect as interchanging rods and caps". I think interchanging rods and caps is much more risky than interchanging rod bolts. As a testament to that... You can buy and install a whole new set of rod bolts. In fact, some people even recommend that. Of course, it would be a better idea to keep everything together and in the exact same orientation as it was originally, but I certainly don't think it's as high an impact as mixing up all the caps.

I'm guessing the reason it's important to keep the rod bolts in the original location is that they locate the lower bearing cap against the bottom of the rod. Take a look at the rod bolts... there's a thicker section up by the head. That thicker section is a locating shaft for the caps. Now that you mentioned it, I've got to take care of that too. I dropped two of them and I'm relatively sure I got them back in the original orientation. I know they're on the right rod and the correct side of that rod... Only thing I'm not positive about is the rotational orientation. When mine fell out, I put them back with what looked like (in crappy light) the cleaner side towards the rod, but I need to double check them now. Have you looked at yours to see if you can use the oil staining as a guide?

Good progress. I'm with you... I'd put a little sealant around the oil holes and the water holes. The rest of that gasket's sealing work is oil, but it's not under pressure.

Yup. That's exactly what I meant. So the ITM has the timing marks, and according to Dave, so does the OSK.

As suggested, a hook on a slide hammer tool (or a crude substitute) would probably pop that out. Or just let the machine shop take care of it. It won't add any significant cost. Did you get the front one out? If not, be careful drilling that one too. #1 is close behind that front plug.

If it makes you feel any better, that's not the first time I've heard of that. I haven't done it (yet), but apparently it's easier than expected to do that. I don't think you are the only one.

Cool. Those are available all over the place for cheap. And you said it definitely has the timing gashes on the back of the gear?

Definitely weird. Would be more confident in a repair if we knew definitively knew what really happened. That tight side guide is normally under such low stress. I'm having a hard time understanding how a worn chain could cause that failure. That side should always be tight, regardless if the chain is worn or not. Maybe it's in there slapping around side to side and hit some harmonic. Slapping against that guide and setting up some resonance until it broke the mount. Regardless... Let's not do that again. Ever.

That's a little disconcerting. Now I really wonder what happened there!

He said the bolts were still there and tight. The tensioner snapped right off the bolts.

Thanks for that. There are plenty of ITM kits on the web, but I could never find a pic of the back of the timing gear. The pics were always the front side. So what was the kit number you got? Was it the ITM 053-90400? So far, from pics I've seen... TRW S462 has the marks. Beck Arnley 025-0266 has the marks You say ITM has the marks. Melling does not have the timing marks.

Woof. That's not pretty. Would be really interesting to figure out exactly what happened with that. Did the mounting tabs crack off first and then the guide got pulled into the chain? Or did the guide get snagged by the chain somehow and when it got pulled in, the mounting tabs snapped. Maybe the mounting bolts came loose and it was in there flopping around until it got snagged. And then the snag snapped the tabs. So your tensioner shoe was still in the hole? It didn't pop out, right? And for replacement timing sets, it was probably me that mentioned some of them have the timing gashes on the rear and some of them don't. I was talking about it in Av8ferg's thread here: https://www.classiczcars.com/forums/topic/62852-l28-from-82-zx-teardown/?page=2&tab=comments#comment-584389

So the project seems to be going pretty much according to plan. That's good news! (So far.) Yeah, you might get some coolant spillage down into the sump, but I think if you pull the block drain first (big plug on the left side near the rear of the motor) and let the coolant out there, it'll be minimal. I believe that drain hole in the block is lower than the water pump holes. Certainly less than if you pull the front cover without pulling that drain plug first. And if you do get some coolant in the oil, most of it (being more dense than the oil) should sink to the bottom of the sump and come out with an oil change. And regardless, I would recommend that you change the oil after this process just because it's likely you'll dislodge some junk anyway. And nobody likes dislodged junk.

Roger that. Well good luck with it, whichever path forward you choose, and let me know if there's anything I can do from a distance to help.

Exactly. Small reduction in effort, but every little bit helps, right? Other trouble spots? Getting the BF bolt out of the front pulley will likely require impact gun. You got one of those? I recently pulled the front cover off my F54 block, and it was stuck on there pretty good. I had to really work at it to get it off, and that was with the head already off!! It can only be worse if you have it pinched between the head and the pan. But the bottom line... If both bolts came out of that guide, you're gonna have to pull the front cover. No way you can get to that lower bolt with the cover in place.