Captain Obvious

I find the pictures from all the FSM's a little confusion because they don't put the FRONT notch up top. All those FSM manual pics have the piston pin running side-to-side instead of top-to-bottom, and I just find it confusing because I want the notch at the top. To get the FRONT notch at the 12:00 position, you have to rotate that sketch. And also interesting to note that they do not specify "FRONT" at all. Just the piston pin direction. Seems it really doesn't matter which is FRONT. You could rotate that sketch either direction and it would still be right. I rotated it and put on the two possible FRONT notch locations: Either of those FRONT locations would follow the "rules". The FSM shows the pressure rings all at 4:30 and 10:30, but I don't see any reason why 1:30 or 7:30 would be any different.

My understanding is that the starting offset was to maximize the length of the path between compression and non-compression. The longer the labyrinth, the less leakage. And staggering the gaps +180, -180, +180, -180 is the best you can do. And while some things are designed to "walk", I don't think the rings are one of them. I believe the gaps are intended to stay where you put them. But all of this is why I'm hoping some of the engine builder experts will chime in. I have all my rings on pistons but haven't put the pistons back in the block yet. I still have time to completely change all my gap locations if someone throws their body in front of what I'm planning.

Good timing. I'm messing with the same thing right now. I didn't find "clear cut positions" anywhere either, but I believe the overarching gap position rules go like this: 1) All the gaps should be at a 45 degree angle away from the piston pin center 2) The 4th (bottom) ring and second ring gaps should both be in the same as position 3) The 3rd ring and top ring gaps should be 180 degrees away from bottom and 2nd 4) oil wavy ring gap (expander) should be 90 degrees from all the other rings Some additional rules, not specifically related to gaps, but since we're talking about rings, it's probably appropriate to mention them here: 5) Put the wavy expander in first and make sure the split portion is titts down, like an "M". 6) The thin 3rd and 4th rings do not have a top/bottom. Doesn't matter. 7) 2nd and top rings DO have a top and bottom and make sure you have identified that and get them on correctly. So, interpreting those rules... Put the waver scraper ring on first. Pick a position for the gap. The rule is "45 degrees from piston pin", so you have four choices - 1:30, 4:30, 7:30, or 10:30. And then once you have picked a position for the expander, the rest of the positions should fall into place. An example: Put your wavy expander at 4:30. This mean that all your other gaps must be at 1:30 and 7:30. Fourth and second being the same at either 1:30 or 7:30, but third and first must be opposite. I looked closely at my block and tried to figure out where the rings originally were from the factory and then when I put the new rings in, I tried to put them somewhere ELSE this time. Figuring I would "even things out". Not sure it makes much difference, but that's my plan. Before I put the rings on, I marked the piston tops with sharpie to make it easier for my little brain to keep things straight while moving the gaps around. I'll clean the sharpie off after the pistons are installed. Looks like this: However, all that said, please note that I'm no expert in such matters and give a little time for other people to throw their bodies in front of advice before you put all your pistons in. I'd like to give other people some time to tell me just how wrong I am before you go and repeat mistakes that I've made.

Yeah, that one was a real bonus! I was cleaning that connector with the 100% expectation that it wouldn't have any effect, but (roll eyes) I had to perform due diligence and clean it before I moved on to more difficult solutions. It was just the right thing to do. Bonus!!! Sometimes you win one! I guess I'll keep that new sender lock ring and sealing O-ring in a box on the shelf! Haha!! And buy a lottery ticket?

Exactly. That's what it sounded like to me, but I'm having a hard time believing that he got two senders with the same blob in the same location.

No, I think if it were resistance in the wires (and connectors), it would do what you said... Inaccurate through the whole range. SOUNDS like the sender unit has a dead spot below 1/3 tank, but I'm having trouble explaining the exact same behavior with two different senders. I'm also having trouble explaining how bending the arm could fix this. (But full disclosure, I've never messed with the sender units.)

Well bummer about the seat heater controller thing. So the only option is to buy a new controller? Do they sell just the controller separate from the heating pads?

Right, but because most of the wires didn't line up with contacts, it looks like only two wires out of all of them made contact at all: It's just unfortunate that it only took those two to cause the damage you're seeing.

Chase, So your gas gauge works fine for all situations except when the tank is about 1/3 full? If that's the case, then I'm having a hard time coming up with any answer other than a problem with the sender unit. I know you replaced that and it didn't fix the problem though, right? Does the new replacement act just like the old original sender unit?

I filled up my gas tank yesterday for the first time since cleaning the connector pair at the sender unit, and guess what!!!!?? My gas gauge now reads significantly higher than it used to before cleaning that connector. Here's a full tank now. It used to read at about 7/8 full (even when full), but now it looks a whole lot better: So for me, cleaning this connector made a big improvement: I may still pull the sender unit out of the tank for inspection, but the priority just dropped down on the list a bunch!

Woof. You and electrics aren't getting along so well lately are you? So from the pic above, it appears that only two of those wires are making any connection at all. All the rest of the wires are no-connects. That was enough to fry stuff? That's a bummer.

So that looks OK to me (now that I can see it). I put in a section for "Mid-year changes" in the 260 folder just to see how that would look. I guess the first major question to debate is... Would it be better sorted by item specific changes (like seat rails), or as a design timeline (most likely by year)?

I can't really tell what the wiki style would look like without an example, so I put in a couple years just as a test. I don't know if anyone else can see that categories I put in. Says it needs to be approved by a moderator.

Man that looks fantastic. I sure wish I had something like that in my car. I don't drive it in the middle of winter (when there's salt on the roads), but there's still a significant portion of time before and after that when I would really enjoy seat heaters. I either need warm air blowing out of the dash vents, or I need to stick one hand at a time under a leg to warm them up. As of right now, I still haven't figured out an easy way to get hot air out the dash vents, and sticking fingers under a leg against cold vinyl just doesn't do it for me.

I think the idea is great, but the implementation is clearly up for debate. How about a simple description of "differences from the previous year" and then if there are questions or requests for pics about something specific, they can be added. Just to illustrate things, I tried to pick something that everyone knows about from each year: 72 240: Changed from the four screw round top carbs to the three screw and routed water into the carbs to heat the nozzles 73 240: First year for the flat-top carbs 74 260: Changed the seat rails to a new design First year for shock absorber mounted bumpers 75 280: This is the first year for the fuel injection 76 280: Increased the number of parking brake ratchet teeth Added weather strip rubber along tops of doors 77 280: Changed the seat rails to a new design New sheet metal stampings pretty much everywhere 78 280: Redesigned ignition module which allowed removal of the ballast resistor I'm thinking just keep filling in differences as stuff comes up?

My pleasure. Glad to help. And a hug would be nice too. I'm a lumberjack and I'm OK. So I was a little pressed for time earlier when I posted that diagram and didn't have time to talk about the use of flashing the high beams here in the US. First of all, if we here were to flash the high beams, we would just pull back on the HI/LO stalk twice in rapid succession. More modern cars have a "make-before-break" type of switch now, but back when the Z's were new, you just pulled the stalk twice. And even before that type of control, the homegrown stuff here often used a foot switch operated by your left foot. You would stomp the switch twice quickly. As for the meanings... Just like where you are, there are several different meanings to the flash. I don't know if there are regional differences in the USA, but where I come from: Quick flash at an oncoming driver can mean "I just passed by something that you might like to know about and you should pay attention." Things like debris on the road, animals along the side of the road, police ahead. That sort of thing. A quick flash at an oncoming driver may also be "You have your high beams on and it bothers me. Please put your low beams on." That may be quickly followed by a longer flash if the desired response is not achieved. A quick flash at an intersection means "You go ahead. I'll wait." A flash from behind usually means "Move over, you're driving too slow." The length of the flash is usually commensurate to how frustrated the guy in the rear is. A quick flash on a multi-lane highway after you have been passed by a faster vehicle means "You are safely beyond me and can tuck back into my lane if you wish." Most often used by trucks, but sometimes I'll give trucks that sign even if I'm driving in a car.

Here's what the 72 system (with the FLASH feature) looks like. Other than the addition of the FLASH / PASS button and the passing relay, it's pretty much the same thing they used in my 77. Point being.... I'm assuming that all the years in between are also the same, including yours. You can see that the pair of headlight fuses are not hot at all times, but are only hot when the headlights are turned on. You can also see that the headlight system has no interaction with the ignition switch at all, so the headlights can be turned on regardless of the key position. Same thing goes for the FLASH system. Also interesting to note that when you push the FLASH button, it will turn on the high beam filaments. Full stop. Doesn't matter if the headlight switch is on or not. Doesn't matter if the lights are already on in LO beam. Even if the low beams are already on, it will power both filaments at the same time while the FLASH button is being pressed. Hand drawn in all it's glory: Hope that helps!

The US cars don't have the flash button, so I'm operating without a net, but your diagram does not look right to me. In the US, the headlight fuses are not hot at all times as you have shown. The OFF-ON switch is between the battery and the fuse box. The fuses are only hot when the headlights are turned on. In addition to that, with what you have drawn, the ONLY way to get the high beams to light up is to push the flash button. I think there's stuff wrong... The newest thing I have here is the 72 manual still shows the FLASH relay, and the basic system is pretty much the same as the US with the exception that the flash relay is wired in parallel with the rest of the system and will turn on the high beams even when the headlights are not on. Would it help if I were to sketch up the 72 system?

Yeah, your fuel gauge looks like it reacts the same as mine. Always too low. I haven't done anything else with mine (since I cleaned up the connector right at the sender unit), but I fully expect my issue is inside the tank. Murphy's law pretty much demands it. That Z hasn't come back around on my work sheet yet. I've got all sort of other car work to catch up on. Today I changed the plugs on a V6 Kluger. Including the three invisible ones in the back... That's no fun. As for the bike "teaching moment"... Very nice! Thankfully, tis but a scratch!

Just like Ty did! https://www.youtube.com/watch?v=kBxuVQ6lrAM

Here's some of the stuff I read on the internet. Some threads from HybridZ: https://forums.hybridz.org/topic/51104-differences-between-the-240z-and-280z-rear-control-arms/ https://forums.hybridz.org/topic/64548-stock-control-arm-length/

Haha! One thing at a time, right? So do you have a signal generator? I bet you could just use a 12V square wave to test the tach on the bench. It might require the flyback spike from the coil primary as a trigger, or not. It might work fine with a clean 12V square.

I read on the internet that the later control arms got beefier. Thicker steel and maybe some additional gussets here and there for strength. I don't know if the form-fit-function changed when they got beefier, but if not, even though they are different, they may still be "interchangeable".

Yeah, that's not an option then. So how about pics... Can you take some pics of the carbs you do have? Do you have any documentation that came along with them? Also, earlier you said "both dampers are working to make them rise slow and drop fast." - How did you test the dampers?

I looked here for a spare tach (aka not installed in my car) and I couldn't find one. I know I had one some time ago, but I also remember that I sold one to a deserving desperate forum member at some point in the past. Maybe that was my only spare? If I had one, I'm sure I could come up with a way to test it on the bench. (Easy for me to say, right? ) Anyone want to send me a 280 tach for investigative purposes? Haha!!