Captain Obvious

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!!

Same here. I thought I had a schematic around here somewhere, but I can't find anything. I'll keep looking.

The damper is a "transitional" device to temporarily slow the rise of the piston when there is a rapid increase in the air speed through the venturi. This has the effect of richening up the mixture for a short period of time. The damper does nothing to affect the piston position during steady state conditions. If you're already running lean on transition, then running without a damper will only make that worse. @RS02 , You've got so much stuff going on that I find it hard to get a "baseline" from which to operate. I don't know anything about "Rebello modified" carbs, but my (non-expert) suspicion is if they bored out the throat and changed the venturi area, it will have the effect of leaning out the mixture at the same airflow. So unless you're pulling in more air to make use of the new larger venturi area, then things are not going to work out well. A thinner needle may help mitigate that situation, but I wonder if those carbs were more intended for flat out WOT (track) performance more than street driving. I agree with the sentiment above that it would be a good idea to drop back to a set of "normal" SU's and see what happens. Just so many variables...

I'm a little skeptical about changes like that from someone who may or may not know what they are really doing. It's admittedly unfair for me to question his fix while I have nothing else to propose, but his explanation certainly didn't satisfy me. As zKars pointed out above, there is a 2200 Ohm resistor in series with the tach on the 280's. Another 5 Ohms added to that 2200 won't do squat. Makes me question the mod. When I get a chance, I'll look to see if I have a loose tach around here.

Welcome to old Z ownership.

Once you have shorted out the 5 Ohm resistor, it really doesn't matter if you leave it there or clip it out. However, I have no idea as to the validity of that "fix". Without doing some reverse engineering I cannot provide any input into what that modification does or if it's really a good idea or not. The guy in that video seemed confident in it, but I'm not confident in his confidence. He said something about "running the numbers" and "that resistor in there reduces the voltage"... Well, without seeing a schematic, I'm not sure at all what that means. Might be harmless, might not. Is this a common thing that a lot of people mess with? I might have a spare tach around here somewhere...

So that was "Physics" class? Potentially followed by "Pre-Med"? Haha!! What's your build month/year on your door jamb plate? If you've got a full sized spare, I'm thinking that here in the US, we could call your car a 76, not a 77.

Got your DM and I'll get some springs out to you. Have you verified that your distributor is actually supposed to have two springs? I find it hard to believe it wouldn't, but stranger things have happened. Haha!

Now THERE'S something you don't see every day!

Glad to help. To summarize the sealant the sealant stuff... I've never seen a silicone RTV sealant that said it was recommended to be used in a gasoline environment. All of the ones I've looked at say "not for head gaskets or for contact with gasoline". And while the RTV stuff won't instantly dissolve or burn down, fall over, and sink into the swamp... You can do better. I tried that Motoseal stuff because the package actually said "Gasoline resistant" on it and I've been satisfied in those applications. I'm sure there are other options. All that said... I would NOT use the Motoseal between your carb domes and the bodies. I'd be worried that it would work TOO well and you wouldn't be able to get the domes back off easily. For that application, you want something that doesn't work "as well".

The trick is that the Motoseal is not an RTV (like the Ultra or Supra Grey stuff). Instead, it is a solvent evaporation cure based sealant and not a silicone. Once the solvent evaporates, the rubbery solids remains are not particularly soluble in gasoline. According to the MSDS, it mostly uses the following: XYLENE 2-BUTOXYETHANOL ETHYL BENZENE If you can't find that brand name, there's got to be something within your shores that is similar. Finding it is the trick though.

Neither of those are what I recommend for gasoline intensive applications. Both of those are the grey RTV silicone that I used to use everywhere before I discovered the MotoSeal. (The Ultra Grey is what they cell it here. And from what I can tell, the "Supra" (not Super) is what they call it elsewhere on the globe but it's the same RTV.) I took a look at ebay UK and found the stuff, but I didn't find anything IN the UK. It's all shipped from the US or Lithuania. I'm guessing they don't sell it in the UK. Here's a pic from your ebay of the MotoSeal: And another pic of the same stuff in a different package:

No problem. Good luck with the parts and I hope they have what they say they do! Let me know if you need a spring or two if the other stuff doesn't pan out.

Thanks Wayne! So AK, I'm not sure if you've got the access hole or not. Your sheet metal deck looks different than mine. Starting in 77 they put the stiffener frame rails on the interior side (top side) instead of underneath (gas tank side). My guess is that since they had to use the raised floor for the spare tire anyway, they figured they had the room and moved the stiffener braces. It doesn't look like you've got those braces. Another way to tell... Do you have a full sized spare, or the collapsible inflatable one? I'm thinking you've got the full sized spare and rear decking that we would call "76" over here. There's no guarantee that what we call "77" over here has to be the same as what you got in the UK.

So I'm confused then... If you got the "improved" 77-78 cars, it sounds like (other than the engine), it's the same thing I have. So why don't you have that convenient access port-hole in the rear deck for the fuel sender unit? is yours an early 77 or something?

Well I found the distributor basket case I was thinking about, and it's a D6K82, so I was apparently very wrong about it being from a 240. In fact, the info I have indicates it's at the complete other end of the spectrum and came from an 83 Non-turbo. But here's the good news... The mechanical advance specs are similar to your D612, and if your distributor is SUPPOSED to have two springs, then I would assume that using one spring from my basket case is going to be way closer to the original design than just one spring. in yours So short story? Whatever you want from this distributor is yours for the shipping. Just let me know.

Well honestly, I was mostly kidding since @AK260 left me little choice with my first comment. But some more detail? I'm no sealant expert, but I think that in the application where AK used RTV silicone, it'll be "fine". It's not bathed in gasoline, and it's what I would consider a "low stress" application. I wouldn't use it to seal the fuel bowl gaskets or the carb to intake manifold, but at the end of that throttle shaft, I think it will be good enough. So after posting last night, I was able to poke around on the computer a little and found some detail about my testing and my pics. I don't remember what type of carb I was messing with that spurred me into the experiments, but I did the following... I put a dab of both Permatex Ultra-Gray silicone (my go-to) and MotoSeal on an index card and let them both cure for a couple days. Looked like this: Then I cut the little dabs out of the index card and gave them a couple day immersion bath in gasoline: Then I took them out and gave them and compared the results. Here's the ultra-scientific "poke test": MotoSeal after poking: Silicone poke: Silicone after poke: And here's the summary result: And then after the soaking, I let them sit on the bench and dry out for a couple more days, and here's the results of that: So after that testing, I've stopped using the Ultra-Gray and have switched over to MotoSeal in gasoline intensive applications,. I still use the Ultra-Gray for most everything else that doesn't involve potential direct exposure to gasoline.

I used to use that silicone RTV style for pretty much everything, but a couple years ago I switched over to Pertmatex MotoSeal for gasoline intensive applications. I don't know if you've got something similar on your part of the globe, but I assume you could find something. I ran some tests on both in gasoline, and the MotoSeal came out to be the clear winner. I think I've got some pics around here somewhere if I could only find them...

You used the wrong paste.