Captain Obvious

Much better on the washers. Back side washers too, right? Hey... Someone has to ask.

Beautiful. One question though... Are you sure you got the T/C rod bar washers in the correct direction? Could be an optical illusion caused by all the shiny bling, but they look backwards to me. It looks like you have them convex side out:

That pin is hardened. Even if you would manage to weld it back together, you would have to heat treat it after the welding. So in other words..... "No".

What everyone else said. That's added value right there, isn't it?

Awesome! Glad it was that simple and you're back on the road!

Oh yeah? Well.....

The FSM actually says you shouldn't have to address the peened (they call it "caulked" in the FSM) sections at all. They say just to take them off without messing with the bent portions at all. However....... There was someone here who actually DID try that and it distorted the threads on the stub axle a little. I didn't dig up that thread, but it's in here somewhere. And after seeing what happened to his threads, I wouldn't recommend following the FSM. I would do something to the bent over portions first before taking the nut off.

Oops. We were posting at the same time. Glad to hear that the pistons are rising smooth now. It's pretty much impossible to get "too much" oil into the damper stalk hole. If you put too much oil in the hole, Archimedes will displace the excess when you insert the damper check valve jiggly bits into the carb. And that excess will just run down into the carb and be burned by the engine. So I'm not sure at all about the current problem now. Not sure what you are trying to describe. But good progress so far!

Yeah, it's tough to describe how a properly working piston should feel because you have to use subjective words. If you've felt a properly working one then you know what to look for, but if the only thing you have to convey info is words, then it's all subjective. And don't stretch the springs unless you understand the implications. You shouldn't have to do that. OP, the pistons should be "hard to lift with a finger" and they should "leave a dent in your finger" when you lift them. It should be "hard" to get them started and you'll have to "pry them up with a finger tip" at first when they are fully down. So here's a less subjective way to check to see if the damper pistons are working properly.... Take the damper stalks out completely and lift the pistons. Then put them back in and see how hard it is to lift the pistons. It should be "much" harder to lift them when the dampers are installed. If there isn't "significant" difference between the forces required to lift the pistons with and without the dampers installed, then there's potentially an issue there.

Good video. It looks to me like the pistons are rising too rapidly the first time when you goose it and they overshoot. Then they recover where they should be and rise with the engine RPMs as they should. That overshoot situation results in a short lean burst when you goose it. Just like your what you describe with your stumble off idle. In fact, that's the exact reason the piston dampers exist in the first place. There are typically two things that can typically cause that: 1) The first thing to look into is... Are your damper dashpots working properly? Because if they aren't then it won't matter WHAT kind of oil you're running in the carbs. So when you stick a finger in and manually lift up on the piston. Is it hard to lift up, or can you push it all the way up easily? Does it leave a dent in your finger? 2) The other thing to think about is the oil (or ATF if that's what you are using). If the dashpots are working properly, then maybe the oil is too thin allowing the piston to rise too quickly. Simple thing to try is running some heavier oil in there. I used to run ATF, but recently switched to 20W-50. But you have to make sure the dashpots are working correctly before you start trying other oil weights.

What Mark said... What kind of oil did you use to fill the damper tubes on the SU's when you put them on? It sounds like a classic case of too thin of an oil or a damper dashpot not working properly. Can you elaborate a little on the "chatter" you mentioned with the pistons? Any chance you can take a video of that?

To answer some of your questions directly... The initial mechanical setting of the float level is just to get into the ballpark. The sight glass is the real test. The desired level does depend on the carb design though. What year are you working on? 73 or 74? Can you post a pic or two of the power valves? That's another easy way to know for sure. However, without even seeing the carbs, I suspect the fuel level should be right at the dot in the middle of the window and your level is way too high. Tips for cracking the power valve open? Not really. The gaskets hold tight and can make it difficult to separate the wafer stack. Other than brute force, I don't have any suggestions. And testing the carb off the car? I don't have any way to do that. If it was running great one day, and then the next day it wouldn't start at all, I'm not convinced that it was a carb problem in the beginning. But now that you've opened them up and let the magic out, there might be one now. Did you try starting it by holding your foot down a little on the pedal while you cranked it?

Wow Geoff, So sorry that happened. Glad everyone is OK. I'm gonna stop complaining about my car problems now...

Shhhhhhh..... Zed Head, I could take the back half of the cam out easy. Maybe I'll do that (if I can sneak some time in the garage when I "should be working on other things")

Excellent. That all makes perfect sense. A cold lean idle is an unhappy idle. You want every molecule of air going through the venturi, not around it! Glad you found it!!

I haven't decided what path forward I'm going to take, but whatever that path, I will be sure to take pics. I did not look for stuck valves. I haven't done anything else beyond that short video clip other than go out to the driveway and open the hood on the 83 and look inside. I was NOT getting bored. I'm so backed up with car work at this point that one more thing is absolutely not desired at this point. In fact... I'm cleaning up after dinner last night and the hot water coming out of the tap is way hotter than usual. Dangerously scalding hot. Take a look a the water heater and it's got water dripping from somewhere out the top. Not good... I killed the breaker. SWMBO isn't going to appreciate cold showers. Especially if I'm out in the driveway working on my car. Anyone want to help me wrestle a water heater down into the basement? I'm getting too old for this crap.

First time I hit the key, I just wanted to see everything rock around like it's supposed to. It was so striking that I had to do it again. I was like "Wait.... What???" I was stunned. Took a couple seconds to sink in, and then I was really bummed. So what are the prospects for bent valves? Is the L28 an interference engine?

Haha!!!

No, I do not. The one in there is an "A" grind from 1977. I've got an F54/P79 combo here from an 83. That might be the same cam, but if I'm going into that motor, it's for the intention of dropping it in where my existing motor is. LOL. Maybe I will! Bug spray and sunscreen!

Haha!!!

I bought this car used a couple years ago, and I don't know the history of the engine. I did get some pics from the PO including some shots with the head off the engine, so I know it's been apart at least that far. I don't know if he ever pulled the cam off the head or took the towers off the head. It's stock parts (cam is Nissan "A" grind stock), but I don't know if it's original to this car. I suspect that it is, however. I've been driving this car on that engine since I bought it, and have never had a hint that I had trouble like that brewing. No idea what happened. I was not at high RPM's when it let go, and I don't think I've ever hit redline with that engine. I take it to maybe 5K often, but that's about it. Anyway, no idea why it finally let go, but it's gone now! So I haven't dug into it at all and don't know if that rear cam section is seized in the journals. I kinda doubt it. I suspect it spins just fine. I'll find out when I start taking stuff apart. And about a path forward... I could either put a new cam in that engine, or... Exactly what I was thinking as well. I kept telling you I was going to do it this summer, right? The only problem is that it's Z driving season right now and it would be faster to toss another cam into my existing engine. Yeah, me either. That's the "whatever remains, however improbable, must be the truth." part!

Sorry guys. I was trying to be cute and I guess the issue doesn't come across so obviously in the video. That's what I get for holding my antique crappy camera in one hand and reaching in with my other hand to crank the engine. If you look at the camshaft while I'm cranking the engine, you'll notice that only the front half turns. The back half doesn't move at all. My crankshaft completely cracked into two pieces. This is just behind the center support bearing:

Uhhhhh.... Did you watch the video?

So I'm out driving around today, just minding my own business... All of a sudden, out of the blue, it starts running exceptionally poorly. Somehow (still not sure how), I managed to limp it about five miles home. Get home and start the troubleshooting. It's completely missing on the rear three cylinders and front firing out the intake like the timing is way off. So, what can cause a complete miss on the rear three cylinders and run like turds on the others? ECU? Nope. That's not it. Dropping resistor? Nope, not it either. Bunch of lash pads fly out? Nope. "When you have eliminated the impossible, whatever remains, however improbable, must be the truth." https://youtu.be/4nE4QhK4LMY Woof.

Everything on the engine works better when warm. They really don't like running when cold, especially at cold idle. In fact, that's why there is usually some sort of idle speed boost method employed that can be engaged at cold idle. For the 240 and 260 Z's, that idle boost is built into the choke mechanism. And for the 280's that function is performed by the AAR. The point is... If you are not employing the use of some sort of cold idle boosting method, or if your boosting method is not artificially raising the idle enough, then it would be perfectly normal for the idle to go up as the engine warms up. Other thoughts? If you are having some issues when you first hit the throttle you may be running a little lean. A lean cold idle is an unhappy idle. If you're running a little lean, the idle would get better when the engine warms up. That all seems to dovetail together. Sounds like you feel reluctant to come to the forum for help? Don't worry about that. Bring it.