Captain Obvious

Haha! x3! As for the RTV issue... I know that gaskets are supposed to seal all by themselves, but even with surfaces surgically clean, I've not had a perfect record of success in the past. My current philosophy on the topic is to think about a bunch of questions: Is it a "maintenance required" area like a valve cover? How much of a pain is it to do the gasket again if there's a problem? How much of a mess is it going to make if it starts to seep? Have you had trouble with it sealing in the past? If the job is a royal pain in the arse and I'm pretty sure that I'll never need to go in again, I'll use RTV. Especially if it's bathed in oil and going to make a mess if it seeps. Things like oil pans, timing covers, input snouts on the transmissions fit this category. If the job is relatively easy and history shows I'm likely be in there again, I won't use it. Carbs and valve covers fit into this category. Intake manifold? How many miles on the motor, and do you think you'll need to be in there again soon? Which RTV to use? I used to use almost exclusively the Permatex Ultra Copper stuff because of the higher temperature rating, however, a few years ago I switched over to mostly the Permatex Gray stuff instead. I've found the gray to have much better adhesion and better resistance to oil creep past the joint over time. Also, the gray has a significantly higher durometer (hardness) once cured and better for gasket squirm. I don't have the packages in front of me, but as I remember, the temperature ratings of the two weren't that far apart. Maybe 100 degrees or so? I still use the copper if I'm really concerned about the temp. Remember though... YMMV! :classic: One last thing about the RTV's. It's a pet peeve, but I hate seeing big ol' squeezed out beads of sealant from using way too much of the stuff. Remember that if you see a big bead hanging out on the outside, then you've probably got one on the inside as well. I put it on with a syringe. Fill the syringe from the tube and then do the application with a small orifice and use a tiny bead of the stuff. I consider is success when I can juuusst barely see any sealant squeezing out of the joint in most spots, and maybe none of it squeezed out all in a few. Think about where you need to seal and where you don't. You don't need to seal the mounting studs to atmosphere. You do need to seal the intake holes to everything. Only put it around where you need it.

Oiluj, Nice seats. Where did you get the seat covers?

It sounds pretty normal to me. I wouldn't go poking that nest. You don't want that stuff to fall into your cylinders. My (amateur) advice is to put the new gasket on and forget you ever saw anything in there. If you clean it off, it's going to come back anyway.

I understand what code cutting is. I thought you were suggesting that all I needed to do in order to fix my lock problem was to get a fresh new key cut from wafer codes. But as you can see, the problems run deeper than that. You identified the last wafer correctly as being used for key tip alignment, but the first wafer (the one I identified as zero) isn't for the buzzer. Wafer zero is used to retain the fully loaded cylinder plug in the lock shell. It snaps out when the plug has been fully inserted into the shell and prevents it from being pushed back out. I'm probably not using the correct terminology, but I'm sure you know what I mean. The buzzer switch is actuated by the rod located near the center of the pic. Good memory for not being inside of one of these things for a while though! I haven't even gotten to the door locks yet, but I do remember those lazy cams from a previous Z many years ago... I've fixed them in the past, but I don't remember what I did. Maybe it will come back to me when I've got the door locks off and in hand. Heck, maybe I'll get lucky and those cams aren't all worn out!! Yeah, right. But the ignition lock is my first priority and it sounds like it won't be too hard to find the correct wafers in the boneyard. C'mon spring!

Thanks Unkle, I was hoping you would show up here. I did a bunch of searching before I posted, and didn't find answers for the questions I was asking, but I did see you very prevalent in most of the lock discussions. I realize that new wafers might not be the answer if the housing is a mess too, however, I think mine is salvageable. Here's where I am right now, and you can see why I was asking about the wafers. My lock is way beyond code cutting a new key to fix the problem. Note the bent wafers from positions 1,2,3. I just bought this car and it needs three different keys for locks on the car. I'm planning to re-key all the locks to the same key and change the key pattern while I'm at it. I was figuring to gather a bunch of wafers from donors and use the best of the bunch to create my own new key pattern. I'll cut the first key myself and then use that as a master for future dupes. So you're thinking that they used the same wafers through the 80's? By the way, I was calling them "wafers" because that's what I saw them referred to in past threads on the topic. Before reading those threads, I would have called them "tumblers". What do you call them?

My ignition lock on my 77 is sticky. Sometimes the key turns easy, sometimes not. I assumed that it was worn inside, so I took it apart, and yes... It's pretty bad. So I'm going to rework all the locks on the car and I've got some questions before I start... First, do all the locks on the car share the same wafers? By that, I mean do the doors, hatch, and ignition lock all use the same wafers and springs? Second, what other Nissans used the same wafers? My local yards have no first gen Z's, but there is the occasional 300ZX or mid-eighty's Maxima. Do they use the same wafers as the S30? Any other (non-Nissan) cars that use the same wafers?

So what about the piston springs? The springs are the ones that came with the carbs from ZT and they look OK? And when you get a chance, try that steady state test again and see what happens.The damper should only be a transitional thing. It's effects shouldn't last more than a second or two. I think it's time to swap the carbs with a set that's known to work well on a different car. Shotgun if the problem is with the carbs, or something else on your car somewhere. Mmmmmmm...... Flat tops......

So there's no spider webs in any of the holes on the intake face of the carbs? No gasket sealer goo smeared in the holes? When you're running with no air cleaner, the gaskets between the carbs and the air cleaner are gone too, right? Nothing on the intake face of the carbs except aluminum. What about suction piston springs? Any chance you're forgetting to put them in? I know... I just gotta ask. Did the springs come with the carbs from ZT? When you're popping at 5K, what happens if you just hold it there? If it just keeps popping and never smoothes out then we should be able to rule out damper issues (wrong oil, not enough oil, check valve not working)... Really sounds like a lean midrange needle tuning issue, but there's just no way that should be the case with the SM's. Have you considered switching to the flat tops? I'd be happy to guide you on a journey to the dark side.

I'm not surprised that your car runs OK with the needles the way you've set them. It's not a huge difference, and as beermanpete says, you can compensate for it with nozzle adjustment. It's a little less than one turn on the nozzle knob to make it essentially the same as setting them at the bottom of the groove. However, the correct way to set them is to put the shoulder flush with the bottom of the piston. That manual that Pete posted is pretty blurry, but a similar picture appears other literature as well. They're all set the same. I'll see what I can dig up.

The purpose of that canister is to capture and store gasoline vapors that evaporate from your gas tank while the car is parked. The vapors are stored in that can, and the next time the car is started, those stored vapors are sucked into the engine and burned. As a temporary fix until you find yourself a new can, you should be able to cap the line that comes from the throttle body and leave the nipple on the carbon canister hang open. Done that way, the engine will still suck a tiny bit of the vapors, but not as much as it should. So the plastic nipple that snapped off... If it's the one that goes to the same "T" as the distributor, then that's the one that goes to the plastic CAP on the canister, right? If that's the case, then you should be able to just replace the cap, not the whole can.

So the wideband showed exactly what it sounded like. At the same RPM, you're 16 lean at part throttle, but flat 14 at WOT. At the same RPM... Does the same thing with the stock needles. Maybe even a little worse. That makes sense, but there's no way you should be lean with the SM's OR the stock needles. It's not fuel delivery because you're clearly not running out of fuel. It's not your "typical fixed" vacuum leak because if it was bad enough to cause that much of a problem at 5000RPM part throttle, then it would simply ruin your idle. So... What can look like an RPM variable or throttle position variable air leak? - I think I see a cap on the port vacuum signal on the front carb... If that cap or the nipple it is connected to is leaking, you wouldn't have a vacuum leak at idle, but you would have one as soon as you opened the throttle. That leak would be "fixed size", but wouldn't affect idle. Would make your WOT numbers higher as well, but the SM's might be making up for it due to the fact that the SM's are way richer at the tip. Or, what could cause the suction piston to raise too much, too soon? - Maybe some restriction on the atmospheric vent side of the suction piston? Something in the way of the vent holes to the air cleaner? What are you doing for an air cleaner? I don't see anything in your pics. Also, I see that your bowl vents are not connected to anything. Is it always like that, or is that just for the pics? What do you connect your cam cover vent to? Anything? BTW - Have you talked to Z Therapy about this? I love a good mystery, but it's got to have an good ending! All of the literature says that shoulder of the shank should be flush with the bottom face of the piston, not flush with the bottom of the venturi groove. That means you should be able to see like .035 worth of shank.

I have verified the low pressure with a mechanical gauge. Other than that, I haven't looked into the details at all. At this point, I'm hoping that it's an oil pump. The other alternatives are much more unpleasant.

You can get a replacement anywhere used parts are sold. You could bypass it if you do it right, but there's no performance cost and there are eco-benefits. I'm a tree hugger.

Gotcha. I was assuming after reading that paper that since the pressure peak to achieve MBT usually ended up around 15 degrees or so after TDC that you couldn't possibly knock if the wave occurred that late. Thanks again for all the education and the willingness to help the ignition challenged. So back to my original question, I don't see any significant advantage to changing the Z's original port source to a manifold source. Once you're off idle, the port source is the same as a manifold source anyway, and I might be gaining some idle stability with the port source. I will also have lower idle NOx with the port source. Sound about right?

Nissans newer injectors are side fed and mount into the fuel rails in such a way that you can pull them individually. Great idea. However...:mad: [RANT] So they go through all that effort to design injectors that can be pulled individually without messing with any other part of the fuel rail, and what do they do on the 90-96 300ZX??? They put that big stinkin' upper plenum on top and make it impossible to get the freakin' injectors out without pulling ten million vacuum lines, sixty throttle body coolant lines, fifty-nine thousand electrical connectors, all the DIS coils, all the PCV plumbing.........:stupid: And once you can even GET to the injectors, they are so snug into the fuel rails that it takes a space shuttle worth of upwards force to the them OUT of the rails. [/RANT] OK, I feel better now. The bottom line is... If think the 280 is a pain, try a 90-96 300ZX!

Genius! As for the so-so ultrasonic cleaning results... Did you hold the injector open while it was in the ultrasonic bath? Do the early Z's have filter screens in them? It's been many moon since I messed with 280 injectors.

I haven't determined the build month of my 77, and I don't know what previous owners did to it. I have no reason to believe that it's not stock, but who knows? One of the reasons I was asking about all this is because I've got low oil pressure on my 77, and I know that a leaking spray bar could be one of the reasons for it, especially after seeing just how leaky my rickety original spray bar was on my 74. Anyway, unless a previous owner put an internally oiled cam into my spray bar head and didn't cap off the journal holes, that's not my problem. Haven't looked into it yet. C'mon spring!

I understood that, and I think he did a great job of explaining MBT as well. It's just such a shame to spend all that time and effort only to have something like that happen at that end. Grades are grades. I suspect he ran out of time or contracted senioritis else he would have fixed the issue and run the test again. Yes, and he made mention of that in the paper as well. Something I forgot to ask you about earlier. I was asking about using a knock sensor and always advancing until right before knock, and you said: I now understand how you can over-advance beyond MBT if you haven't yet reached the knock limit but have reached MBT, but why would a knock limit stop you before MBT? Is that because of false triggering? Seems from that paper that the peak pressure is pretty short lived, and I'm not sure how you could possibly knock before you have even reached MBT. What am I missing?

Thanks Leon, that's good stuff there. That thesis paper was definitely deeper than I needed to go, but I made it through. Good to know that there are smart people out there still working on trying to eeek out more usable power from the same amount of gasoline. I'm surprised this topic so quickly included calculus. Two things in that paper that really stood out to me... The first was that there's actually (what I consider) a pretty wide timing window while still attaining 99.6% of max torque. Seems you can miss the perfect spark timing point by +/- 2 degrees without making that much of a difference in the final outcome. The second thing that hit me was that his original purpose for the whole paper was an attempt to use the ionization current as an indicator of the perfect spark timing point, and it seems that there was an experimentation error that prevented him from actually making that conclusion. Maybe I'm misunderstanding the paper (which is quite possible), but my interpretation is "I tried to this, but there was something wrong with my test setup which made my experiment results unusable". Seems unfortunate to spend that much effort on the subject, only to have that let-down conclusion at the end.

Steve, that all makes perfect sense to me. Thanks for that. PA separates their inspections into "safety" and "emissions" and I've had my state safety inspection license for years. I never bothered to get my emissions cert, and I've been kicking myself over it ever since. Now the prices have gone way up on the training classes, and I can't justify the cost for "hobby" use. Also, these days I suspect there's a whole lot less theory being taught in the classes, and a whole lot more of "Where to find the OBD II port", and "How to change an O2 sensor". :sick: I should have got my emissions cert years ago back when they were teaching stuff like what we're talking about here.

Thanks for the additional info. Looking at that chart I see what you mean about the HC. Almost flat with respect to timing while NOx continues to climb as timing is advanced. So our idle timing is on that chart, but once the mechanical and vacuum advance mechanisms kick in at higher RPM's we quickly end up off the right side of that chart. Do the NOx continue to climb, and do the unburned HC still stay pretty much flat? That would explain why EGR only kicks in above idle. Well that, and it would probably completely ruin your idle stability if it was active at idle. So throwing emissions to the wind and timing for power only... You want your timing to be as far advanced as possible just before you start to ping, right? That would ensure that you're eeeking out the most energy from every charge. How effective are knock sensors? Do they pick up each and every knock, or is more of a "average" thing? If I bolted a knock sensor to the center of my L6 and then went out for a drive with my base timing set five degrees higher than normal, what do you think the sensor pick up?

The drop test I was referring to is done with the pistons and covers off the car. Here's a link to the video that Blue posted in the SU section: What you're talking about (pistons stopping 10% above full down with the carbs fully assembled with springs installed) shouldn't happen. I'm sure you already knew that... So, when this sticking thing happens, does it only happen with the damper valve installed, or does it still happen with the stalk completely removed If you've got some misalignment with the piston against the carb bore, that could be made worse when the engine is running and manifold vacuum is pulling that piston in towards the engine. Can you see signs of rubbing anywhere on the suction piston? How about on the inside of the suction chamber dome? Any scratches?

No, no... Go on with the finer points. I'm cool with that. Why do the exhaust temps go up? Because the exhaust valve opens before the burn has completed and you're dumping still burning gasses into the exhaust manifold? And about those unburned HC? Why don't you just give the burn more time to complete in the cylinder by advancing the timing? That way you could get the energy out of it too instead of just wasting it in the exhaust manifold? I'm assuming there's a reason this doesn't work, but I just have to ask. Before I asked here, I did do a little digging and turned up this document about ignition timing: http://www.corvette-restoration.com/resources/technical_papers/Timing101.pdf This guy doesn't like port advance at all. He talks about it on page four: This makes sense to me, but seems to require an air pump in order to work (which we have - or used to have). But then the question becomes: If you're not running an air pump, does port advance do anything for the unburned HC?

Sounds like the filters were a sight to behold. The flat top filters I've messed with have been clean. Only because everything was flowing around them instead of through them. But they were clean. So now that the immediate crisis has been averted, how do your plugs look? And have you figured out the correct yoga position to view the sight glasses?

Our Z's use ported vacuum for timing advance. So what's the theory difference between port based vacuum advance and simple manifold vacuum advance? I'm not a timing guy, but I got the basics: Manifold vacuum is highest at idle, lowest at WOT, and in-between when in-between. Port vacuum on the other hand, is zero at idle, highest just above idle, and the same as manifold vacuum everywhere else. I guess the question is "why"? Why do they eliminate the vacuum advance at idle? What's the advantages? Normally, the vacuum source is used as sort of an engine load sense device. In other words, when the engine load is low (like at light cruise) the mixture is lean and you need more time for burn, but when the engine load is high (like at WOT) the rich mixture takes less time for burn. No problem. But following that concept... Wouldn't the load be lowest at idle? I've done some web searching and have seen some theories that draw a link to emissions reductions and port vacuum, but I'm a simple follower and can't tell established truth from speculation. So, we got any timing experts in the house?