Captain Obvious

Is it my imagination, or is it conceivable that I really tell the difference between regular and premium by the smell? Premium smells a lot "sweeter/smoother" while regular smells "sharper/harsher". I'm no wine guy, but I think I got a pretty good nose... Is this my imagination?

Are you sure that you just aren't able to develop enough pressure to crack the valve open? Been a while since I've been inside one of those buggers, but isn't there a little spring inside keeping it closed or almost closed when static? Thinking that maybe the fuel pump has enough ummph to push the valve open, but your lungs don't? Maybe the spring is stretched a little too long? Do you have more than one that acts like this, or are they all the same EXCEPT for the one that acts this way?

I wouldn't worry too much about the different raw castings. I would expect that those rockers are not cast one at a time, but in fact come out of a multi-cavity mold many at a time. The parts that come out of the same cavity of the same mold should be like peas in a pod, but probably differ (innocently) from parts that come out of other cavities even within the same mold. I haven't looked under my valve cover to see what mine look like, but that's what I would expect. There's no way they were casting these things one at a time when they were used twelve per engine. Doesn't mean that the rebuilder didn't just grab random rockers off a pile, but just saying that Datsun probably did the same thing back at the factory and (if done right) there shouldn't be anything wrong with that, if done right. If done right.

Awesome. Well have a great time, and hope you can hook up with the local Zedders!

Hey boys... Look what I got heah! I gots no input as to where the Z's are at, but just wanted to let you know that I'm jealous that you're going there and I'm not. I've heard that it's one of the most beautiful locations on the planet. Hope you find a local to show you around! BTW - Business, pleasure, or both?

Even if the FPR got completely stuck shut on the outlet, the pressure in the system should have only gone up to the dead head pressure of the fuel pump and the system still shouldn't leak even at that pressure. So keep the fire extinguisher handy, keep a keen nose, and good luck with the hunt. You know it'll be back. Most likely you'll be dressed nice, it'll be raining, and you'll already be late. My friend Murphy works on these kinds of problems all the time.

Right. Is that not what's happening?

I know. That's exactly why I'm trying to scare you off the 300. Did they make the Prelude or Integra with a T-top? I know they made a Fiero T-top... That'll satisfy your need to tinker. You'll hate lots of other stuff about it, but you'll love the T-top! If you want details on the Fiero or more info on the 300ZX, shoot me a PM. I think we've derailed the OP post completely by now!

I didn't buy my 300ZX because it was the descendent of the first gen, nor did I ever expect that it would be similar in any way. My comment was meant more to say that If you're simply looking for something fun to drive that has T-Tops, there has to be other better (IMHO) choices than the 300ZX. My 300ZX was in excellent condition. Needed nothing. Sounds great, right? Well not completely. I like to tinker. No... I HAVE to tinker. And I found that car very difficult to tinker with. I consider it over-engineered, and mine wasn't even a TT! Mine was a 2+2 (which in the states means it's a NA and has T-Tops) and the TT is an order of magnitude MORE complicated. Even I dreaded working on it. Heavy, over-engineered, expensive to fix, not "nimble" at all... A "sporty looking" luxury cruiser. Open the hood and look around and try to see the ground under the car past the engine? Forget it. Packed too tight. And somehow they managed to stuff two turbos in there on the TT??? Anyway, I didn't intend to 300ZX bash. They're beautiful, and through the same theory that bumblebees fly, they can be hot performers as well. Just saying that I've spent many hours in both seats and I'm much happier in my smelly, slow, creaky, always something needs fixin' 280Z and if I were to replace my first gen with something else, it wouldn't be a 300ZX. How about an old Porsche Targa? You got the $$?

Bummer... The intermittency just makes me nervous. You know the problem didn't magically go away by itself forever, right?. A smoking gun (not to be confused with a smoking car) would really be nice on stuff like this. I had a (non-Nissan application) leaky injector that leaked slowly out through one of the seams in the injector body. But it wasn't intermittent, just slow. Good luck with the hunt. Maybe you vurped a little into your carbon can? Shouldn't happen, but just tossing ideas.

I had a 94 300ZX for a number of years. I sold the 300ZX and bought the 280Z instead and I'm much happier with the result. I know everybody is different, but I'm not sure you'd be happy in a 300ZX. It's really hard to describe, but there was just never anything visceral about it with me. Sure, T-tops out on a beautiful day was a wonderful thing, but other than that, nothing. The insignia says "Z" that's about it. There was nothing else about the car that reminded me of the first generation.

Wait a minute... I suspect there's a little communications issue here. When Blue and I asked what "needles" you were using, we were talking about the long straight needles that install in the undersides of the suction pistons, not the float bowl valves. My suggestion would be to stop referring to the valve that the float tang pushes against as a needle valve and simply call that one "the float bowl valve" instead. So about the needles... The stock needles for the first couple years are N-27's but often they have been replaced with SM needles from ZT. Blue has had issues in the past where the needles that came new in rebuild kits were completely unsuitable for use in the 240 roundtops. So... What needles do you have installed in the suction pistons?

Yeah, beautiful car. And you're right. Way too pretty not to be running better. So I thought somewhere you had mentioned that you were running stock needles, but after re-reading the thread, I didn't find it and am assuming I imagined that. So I second Blue's question... What needles are you running? Did you find that thread where Blue and I were exchanging stories about not being able to get the float bowl levels to adjust predictably? Don't keep adjusting the tang so many times that it cracks off. The 240 floats aren't easy to come by. Last I heard, ZT was close to having repros done, but until they're in stock, you should treat them as irreplaceable? Blue, he's in Atlanta Georgia. If he weren't so far away, I'd pack some tools and go help.

You're smarter than that! Everything Harry tells you is a lie...

I didn't look anywhere near that good when I turned 39. And it's only gotten worse.

Yes you had better. Hope you get to the bottom of it soon. Fuel leaks like that are a pain in the butt. I did a little digging into devices to help find a leak and research indicated two things: 1) The typical human nose is one of the very best detectors to find gasoline leaks. It is extremely sensitive to even small amounts, and 2) The human nose unfortunately gets "saturated" very quickly meaning that you very quickly lose the ability to detect the scent. In other words, it works great, but for a very short amount of time.

I can probably explain why you didn't see gas when the engine was hot. The engine was so much higher than the boiling point of the gasoline that it vaporized almost instantly and didn't form a puddle. I would surmise that's why the smell was so strong, but there was no liquid present. As for why it didn't leak once you got it back to the stable and pressurized the system, that's puzzling. I've wrapped injectors, fittings, etc with a paper towel and use masking tape to hold the towel wrap in place. If there's a fuel leak, it'll stain the towel and show up even once dry. Keep it on for a couple days and then unwrap and look for a stain to see if that's where the leak is coming from while hot. And I agree with the thoughts that there's nothing wrong with giving the clamps a snug-up. As long as your hoses have been replaced sometime in the not too distant past and are not all hard and brittle, give 'em a little tightening.

Haha!! It's my calling.

Oh, and by the way... I think the root issue to all of this is that your carbs are (using technical terms) "completely out of whack". I think you've got mixture issues complicated by float levels, carb synchronization, and possibly vacuum leaks. I think you are juggling multiple different adjustment issues and at this point that I would start over with the basics. Pull the carbs. Clean em up. Adjust the bowl levels with a clear tube on the bench. Don't progress any further until you are positive that the levels are correct. Set the nozzles 2 1/2 turns down and put em back on using new gaskets. Get it running well enough to synch the carbs. And lastly fine tune the mixture.

70-72 rebuild kits makes sense. About not being able to get the fuel level in the bowls to respond predictably to changes in the float tang, I've been there too. Been a while, but I remember having the same unpredictable issues where the fuel level didn't seem to follow the expected path after adjusting the tang. There are a couple threads here on the forum that discuss that issue. but you'll have to search for them. Blue and I were discussing it a few years ago. I unfortunately never got to the bottom of what was going on with my carbs, but on the good side (for me), I got the car running great without knowing and I stopped investigating. I'm sorry, but I don't know what the numbers are on the sides of the needle seats are. I think there was at least one needle valve change in the first three years (70-72) but I don't remember if that was for a difference between front and rear carbs or a year-to-year change So jumping ahead a little... What happens if you just put your old needle valves back in?

Gotcha. Check your float bowl levels (you've got sight glasses so it's an easy task) and go over the whole system with a fine comb for cracked tubes and hoses. Half of them are under vacuum and half of them are at atmospheric. And let us know how it goes!

The 73 carbs were the flat top variety and are very different than everything prior. There is little (if anything at all) that is transferrable from 73 to 70. In other words, So I'm not sure what it is you did... Are you saying that you bought a rebuild kit for a 73 flat top and used the needle valves from that kit in your 70 round top carb? And I'm also confused as to how you left the float bowl level situation. You said you couldn't get the levels correct and then what? You just left them wrong? 10mm high is way off and if you left them there, you'll surely run rich. What did you end up doing with the levels in the end?

Regardless of 25 or 125, it sounds like a great starting point and I hope you have a great time with it! Out of curiosity, are you running the flat top carbs or has someone done a round top conversion some time in the past?

Excellent. Another crisis averted!! Yeah, that's the same alternator test I was looking at in the manuals. What's got me is that the text instructions seem to be in disagreement with the test wiring diagram. I know what they were trying to accomplish, but I don't think the translation turned out very well. Glad you made more sense of it than I did! Glad you got it figured out, and if something insurmountable comes up, remember my offer to lighten your burden. BTW - Are you sure it's 25K miles and not 125K?

I took a quick look through the FSM and didn't find that alternator test procedure. Only thing I found was a test on EE-19 (74 FSM) and it didn't test what you did. Not saying what you did isn't a good test, but I couldn't find that description. So does your CHARGE warning lamp light up when you turn the key to ON before you crank the engine? And what does the CHARGE lamp do once the engine is running? Reason I ask is that while the alternator really doesn't need the charge lamp to be functional in order to work properly, the operation of the lamp can provide some insight into the health and operation of the voltage regulator. Keeping a 74 stock? Cool. You better still be running the flat top carbs! (Edited for the external regulator operation)