Captain Obvious

You can narrow the culprit by taking stuff off... You can take the pinion out and see if your still feel it. If you do still feel it with the pinion removed, you can then loosen or completely remove the friction shoe and see what happens.

Haha!!

I can't accept the mantle described above, but I've messed with a steering rack or two. This "notch"... Do you have the friction bushing shoe tightened down when you are sliding the rack back and forth? Do you have the pinion gear installed?

Not far from me is a town named "Devon". Back when Devo first gained popularity, one can imagine what may have happened to some of the (easier to reach) signs along the roads back then. I may or may not know anyone who participated...

Are we not men?

Pics or it didn't happen.

Haha!! My old Alfa had a knob that did that. But making it even worse was that it was a twisty turn style knob. Ten turns or so to actuate, and ten turns to de-actuate. Not the kind of thing you could do quickly. Darwin was driving!

240Znomad, Thanks for the contribution and another data point. Absolutely agree. And that rounded cup on the frame member is exactly why I had my bushings in rounded side towards the cup at first. Then I kept seeing pics of other people's bushings and they were always the other way, so I switched mine. (Despite the fact that it makes engineering sense to me to put them in the other way.) So I'm not saying it makes sense. I'm just saying that's how I always see them. In reality it probably doesn't matter much. As long as it doesn't cause a caster change or cause the T/C rod to bind during normal movement, then the orientation probably doesn't matter much at all.

That's interesting. First time I've seen anyone actually recommend a direction in print. Although.... They also say the tension rods are designed with a right an a left which is incorrect. So the accuracy of the source is in question. And... If you look at the pic, it sure LOOKS like they have the thicker rubber section next to the washer, not the body: So now that the waters are really muddy? I did a little searching on the forum and here's what I came up with. This guy had bushings with the thinner section towards the body like my 260: https://www.classiczcars.com/forums/topic/44860-my-two-swiss-s30z-fairlady-restoration-build-thread/?page=18&tab=comments#comment-541674 This guy had one bushing each direction (which is clearly a mistake): https://www.classiczcars.com/forums/topic/47472-uhm-i-think-thats-supposed-to-be-attached/

I don't have any technical input at this time, but... @Mike, Why is this thread in the technical articles section and "promoted to the knowledge base" category? Did I miss some fantastic technical solution above or something? Home  Forums  CLASSIC ZCAR CLUB  Technical Articles  Promoted to Knowledge Base  Datsun starts but only runs when key is in a certain spot

Yeah, let me know what you come up with for a source. I do think there has been discussion about the bushing orientation in the past and I think I was involved, but it's tough when you can't even find your own stuff. In the meantime, I dug up some more pics. This is what I believe is the correct orientation for the rubber bushings: And I based that off these old bushings pulled off a 260Z and pictures from other peoples cars. I'm relatively confident that they were original factory and they were installed like this: Another shot where you can see the indent from the convex side of the washers on the rubber side: Sample size of one, but that's all I got.

The washer orientation seemed odd to me too at first, but I accepted it when I likened it to shock absorbers and sway bar bushing washers. They use the bushings and washers as a kind of spherical bearing because you want the shaft to be able to move in all directions. Putting the convex domed side inward helps facilitate that and makes it operate spherically. Oh, and I believe the rounded side of the rubber bushings should be outboard too... Sounds like you may have yours backwards. That one also seems counter-intuitive, and the pics in the manuals are not good enough to be definitive, but I've been into a couple cars now where I was pretty sure the bushings were original and they were installed with the smaller section towards the body and the thicker rounded section towards the washers. When I get a chance, I will dig up some pics of crusty cracked (but original) T/C rod bushings. The pic I posted above is (what I believe to be) the proper orientation of everything. If you're running rubber on both sides, just mirror the rear rubber bushing to the front.

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...