Captain Obvious

Thought of another way to potentially test for pressurization of the float chamber. Maybe you could put a piece of tubing over that vent tube outlet and attach a deflated plastic bag to it? With the car hot enough to be potentially causing the problem, but sitting still, the bag should NOT inflate. But if the bag inflates, then it's an indication that you have gas (vapor, not gasoline) trying to escape from the float chamber. Normally, you have fuel flowing into the carb, and fuel flowing out of the carb, and the whole thing should be in pretty much equilibrium. But what I'm thinking might be going on is that you are not in equilibrium. You might have excess vapor that is trying to escape. Baggie over the vent tube outlet would probably be quicker and easier than clear fuel line? Fire extinguisher handy at all times!!

I'm not thinking that shaking the car exacerbates the boiling. I'm theorizing that the boiling (bubbling, emulsifying, however you want to describe it) is occurring all the time, whether you are shaking the car or not. Theory is that those bubbles are passing into your carb bowl and positively pressurizing the air pocket above the fuel level. When the car isn't shaking around, that vapor passes harmlessly out the bowl vent, but when you shake the car and get the fuel in the bowl sloshing around, you can temporarily close off that bowl vent hole. And when that happens, the positive pressure sends a little glurp of fuel up and out of the vent. In other words... The boiling isn't changing. The blockage is. When the car is sitting still, the vent hole is not blocked. But when the fuel is sloshing around, you are intermittently blocking that hole with a wave of fuel. I also suspect that if you're seeing fuel coming out of that vent hole, then I'd be pretty sure that you're getting fuel pulled out of that "axillary nozzle for starting" (your choke enrichment jet) as well. Might not be as visible as fuel coming out of the vent hole, but that nozzle pulls from the same source and it requires much less vertical lift than that vent hole. if it's coming out of one, I bet it's coming out of both. As for you not hearing bubbles back at that tank, the theory is that the front carb swallows most of the bubbles, the rear carb gets most of the remainder, and tank return gets very little? Maybe that's why you don't hear bubbles back at the tank? And as for the thermostat I was talking about. There's supposed to be a small thermostat in series with the carb coolant lines. It lives back by the bulkhead wall near the rear of the block. Where the coolant lines turn the corner towards the passenger side of the head. On page EC-2 of the 74 manual, they call it the Water Control Valve" and it's a temperature control valve. Most of them are clogged (or removed) by now. I'll see if I can dig up some more info about it.

So sitting still with the engine hot and idling, you can rock the car back and forth enough such that fuel glurps out the bowl vent tube? Wow. In this pic, you can see the round sight glass hole in the side wall on the left, and the oval shaped hole in the lower right side is where that vent tube connects. If the bowl level is correct, you need about an inch and a half of vertical lift to get fuel to spill out that vent tube into the carb throat: Just another view of the same. In this pic, the sight glass hole in on the top, and the vent location is at the bottom: Makes me wonder if you might be vaporizing the fuel in the fuel lines and not having a problem inside the carb itself. It's been a long time since I've seen 260 fuel rails, especially without the heat protective wrap, but if memory serves correct, the front carb pulls off the fuel rail first, and then the rear carb, and then the remaining excess fuel is routed to the pressure regulator orifice. Grasping at staws, here's a theory... You aren't boiling the fuel in the bowl, but are vaporizing the fuel in the lines somewhere, and blowing big disruptive bubbles of gas vapor into your float chambers. And those big disruptive vapor bubbles blowing into your bowls need to escape from the float chamber. If liquid is sloshed even a little bit up into the bottom of the oval vent hole in the roof of the float chamber, the positive pressure in the chamber pushes liquid up and out of the vent tube. And thinking that maybe if the front carb pulls off the rail first, theory might be supported by the symptom that the front carb does this more easily than the rear? Cavitation at one of the pumps maybe combined with high temps causing big vapor bubbles in your supply lines to the carbs? Low pump inlet pressure caused by a supply restriction? Positive displacement mechanical pump up at the engine doesn't like the style of electric pump being used to supply it? Can't deal with the pulsed nature of the demand? To test for this, you could temporarily replace the black rubber fuel lines feeding the carbs with a clear piece of vinyl tubing. That way you can get a view of the fuel supply as it leads into the carbs to see if it's solid or all full of bubbles? If you're squeamish about generic vinyl, there is fuel rated Tygon (usually yellow), but for a temporary test, I think the generic clear stuff from one of the big box stores would be fine. And fire extinguisher handy at all times!! Some additional questions while I'm here... So all the coolant lines are connected. There's supposed to be a thermostat in series with the line that leads through the carbs. Do you know if that thermostat is present, and haha... working? I know, I know... What type of electric pump are you running? And is it in the stock location in back? The stock electric pump would allow for passive pull through, but depending on the internal design, some electrics won't. And lastly... You've got a catalytic convertor? Is your car originally from California, or is it something that you put on? I don't think that a clogged cat would cause the problem, but it certainly wouldn't help keep the temps down.

Haha! I see what you did there.

Yeah, I'm very happy with the way this project turned out. It's a lot easier of a project if you're willing to use the donut spare "as-is" and accept the hassle of dealing with switching two tires in the event of a front tire blowout. The offset of the original donut wheel is very wrong, but again... Emergencies only. Dennis, I'm not sure why you would bother with a mini-spare on your 71. I'd love to run a full sized "regular" tire back there, and the only reason I went through all this work was because I can't due to the reduced tire well diameter on the 77/78's. If I could have run a normal tire, I would have never taken on this project. Why are you wishing for a mini-spare?

That tube is simply a vent from the float chamber to atmosphere. And I know you already know this, but there's no way there should ever be fuel coming out of that vent tube. So, you're positive that your fuel pressure is in spec? And you're double dog sure your float levels are correct? With a good flashlight and a small inspection mirror, it is possible to see the sight glass levels even with the motor running. Have you confirmed that it isn't, in fact, a transient level issue? If you're float level is correct and you're not intermittently overwhelming your needle valve with an overly high fuel pressure from your pump, then maybe you are in fact percolating the fuel in the bowl. Do you have the original heat shields attached to the underside of the float bowls? When you say the bowls feel cooler than the rest of the carbs, are you feeling the bowl cover itself, or the heat shield that is (supposed to be) bolted to it. Are all other heat shielding entities still in place? Do you have the coolant tubes to the carbs hooked up, or have they been disabled? I know it's hot there, and even hotter under your hood, but still...

Here's a couple pics I whipped up a while ago that explain how the stock bushings work. Here's the rear outers: And even though we are talking about rears, here's the front inners. Even though it's the front, the concept is identical:

I have a 77 280 that came with the collapsible inflatable accordion spare and I recently completed a project to replace that collapsible spare with an always inflated newer "donut" mini spare. I bought a T115/70/14 donut spare tire and wheel from a junkyard. It had the correct lug pattern, but the inside diameter was too small to fit over the front brake calipers. It fit OK on the rear over the drums, but wouldn't work in the fronts. I came up with two options. 1) use that donut spare as is and if I ever had a flat on the front, I could put that spare on the rear and move my rear tire to the front, or 2) I could remount that donut spare tire onto an old Datsun wheel that would clear the front calipers. I chose the latter. There is some related discussion about wheel widths in this thread here: http://www.classiczcars.com/topic/49310-narrowest-stock-wheel/#comment-450080 Here's some pics of the project. Spare as it came from the junkyard: Then I bought a narrow older Datsun wheel. The one I picked up is a four inch wide wheel off a roadster. You could use a 4 1/2 early Z wheel, or even a 5 inch wide, but I wanted as narrow as possible. Here's the roadster wheel sand blasted: Markings inside the wheel. 4 x 14 and apparently from May 1965: Roadster wheel all cleaned up and POR-15 coated. Moved the tire from the original wheel to my new spare wheel. Here's my new spare with to the original accordion spare and at the top is the original wheel from the junkyard that the spare tire came on: You can see that the donut is a little bit larger in diameter than the uninflated accordion, but it fits into the spare well: Here's my new spare in it's home: T115/70 D 14 mounted on 4 inch wide Roadster wheel: I had to put the spare on the car and drive it a little just to make sure everything worked out according to plan. So I mounted the spare on the car and drove over to a local park as a test. Steering wheel didn't sit straight, and it drove a little wonky because of the large mismatch on sizes between corners, but it worked just fine for emergencies. And even though it's a little embarrassing looking, here's a pic for proof:

Well when I say should never be, what I mean is "if there is ever metal to metal, it's not normal and there's a problem somewhere that needs investigating". Worn out soft bushings, something not tightened properly, bent/cracked parts somewhere. I haven't analyzed the geometry to the depth that I could put numbers on it, but ballpark thinking about the geometry of the parts... Just imagine how much of an angle would be required on the rear wheel in order to compress that rubber to the point that you get metal to metal contact. Three degrees of toe? Five? Ten? I don't know what the real value would be, but I suspect that if you're rear corner is ever being twisted that far, then you've got a serious problem somewhere. Even if it's a transient. Like I said, I'm not a suspension guy, but it just seems unlikely. Have you seen this with a good condition, properly installed stock setup? Clean rub marks where metal to metal contact has occurred? I don't know what's going on with people using a 5/8 bolt instead of a real spindle pin, but I suspect (didn't measure it) the original spindle pin is 16mm diameter and a 5/8 bolt is a little smaller than that. If that's the case, then who knows what that extra slop inside the knuckle is doing. I think it's a bad idea.

Excellent. Last time I messed with that stuff, I bought the generic non-stainless stuff and cut to length. What you did looks like a much better solution!

Agreed. Those look very nice.

I consider my narrow always inflated spare is a decent compromise of reliability, convenience, safety, and available room back in the hatch area. I think I have some pics, but have never documented the details. I'll put together a thread about it so we don't sidetrack this thread too much. On edit: Here's a new thread for my mini-donut spare: http://www.classiczcars.com/topic/55424-always-inflated-mini-donut-spare-for-7778/

I also think you're on the wrong track thinking the smog pump will fix the issues you're having. I don't know what's going on, but I sure don't think a smog pump will fix it. In general, the problem you're describing here where raw gas bubbles (boils) in the bowl and spills up into the carb throat is called "percolation", not vapor lock. Just like a coffee maker... You boil the liquid in the bowl and it runs up a tube an spills over into another area of the device, Just like a old percolation style coffee maker. So you're saying that it will actually vurp gas out of the carb mouth while the engine is running??? And this is a late 260Z... You running the original flat top carbs, or have you swapped them out for a set of round tops?

I've done a couple installs and I just don't have the mojo. I tried an add-on amp thinking that my head unit just didn't have the nuts. I tried a subwoofer thinking that my speakers just didn't have the lower end. I tried a whole bunch of stuff with mediocre results. I either need to fully embrace the study and dedicate the time required to teach myself how to do it right, or have someone else take the lead. I know I CAN do it. I just need to learn HOW to do it right. It just hasn't been high enough on my priority list yet. I know people are willing to give up their spare, but I'm still holding out. I've built myself a custom always inflated, narrow, space saver spare that fits in the small 77/78 spare well. So at least I don't have to rely on the questionable original spare and inflator bottle, but I'm not ready to cut the cord to a spare completely. My new spare is narrower than the stock spare, and the plan was to lower that rear deck accordingly. I also am planning to install earlier year storage doors on the openings right behind the seats and get rid of the raised deck completely in that area.

I'm no suspension expert, but I got a couple comments. There should never be moving metal to metal contact with the stock bushings. The inner sleeve is longer than the outer sleeve, and that keeps the bottom of the knuckle centered between the two outboard prongs of the control arm. The only points of contact are supposed to be the outer sleeves pressed immovably into the control arm, and the inner sleeves pinched immovably tight to the bottom of the knuckle by the spindle pin and nut. You could, in theory, strain the rubber so much with enough force that you actually move the knuckle fore or aft to the point where the outer sleeve would make contact with the knuckle casting (metal to metal), but in actual operation that's not supposed to happen. The urethane is a whole different animal... There NEEDS to be urethane compressed between the knuckle and the arm in order to keep the arm centered between the two prongs. If you simply can't get those bushings squeezed into place, you could probably remove some material from them, but keep in mind that it's supposed to be a tight fit. Question is "how tight?" and I don't have that answer. Maybe they're just TOO thick in that location, but keep in mind that there needs to be plastic to metal compression sliding contact in that location, as well as the tube through the center of the urethane. And yes... That sliding is why they can squeak. The urethane and stock bushings operate on different principals. The stock bushings torsion, the urethane bushings slide.

Audio gear was also part of what I was messing around with. I made a replacement piece for in front of the strut towers (so I didn't have to chop holes in my original one) and put a pair of 6x9's in there. Glued on some cheap under-covering to try to deaden the boom. Sounds like arse. I have kung-fu in some areas, but fidelity isn't one of them. Instead, now I'm currently running a pair of pre-packaged tuned port speakers that originally came from a small home stereo system. Not great, but better than what I made myself. I'm the guy who puts your amp back together after you blow it up, but someone else does the installs.

Onions. Old Z cars are like onions. Peel them back in layers. So why is it that you're making a new rear deck? Did you not have one before? I'm currently messing around with some changes to mine. I've decided that I want to reclaim some of the wasted space back there.

There's a big difference between mostly done and all done. Mostly done is slightly un-done.

" after i get done with the z car " Huh? That doesn't make any sense at all...

To back up a little and add to Zed Head's info above... It's likely that it's got nothing at all to do with the throw out bearing. Any time the engine is running and your foot does NOT have the clutch pedal pressed in, the input shaft as well as the countershaft of the transmission are spinning. Point is... When your not pushing the clutch in, those two shafts are spinning and it's likely that the whining you're hearing is from the input shaft bearing, or the countershaft bearing, not the throw out bearing.

Makes perfect sense. Now go replace the rest of your droopy filaments. I am Carnac the Magnificent, and I approve this message.

Yeah, the AGC series will be perfect. So if I take a guess as to why you were looking for SFE10's in the first place, I would surmise that you pulled the old fuses out of the fuse block and found a lot of SFE20's in there. Thinking that the SFE series was the correct fuse series, you then went looking for SFE10's to replace some of the lower value positions? If that's the case, then you got caught by that simple trick that at the 20A rating, the SFE and the AGC series are the same length. Where's my dead horse....

Here's some info from Littelfuse: http://www.littelfuse.com/~/media/automotive/datasheets/fuses/automotive-aftermarket/glass-fuses/littelfuse_aftermarket_glass.pdf

Is the original recommended fuse really from the SFE series? The reason I ask is that the thing that makes the SFE series interesting is that the fuse lengths increase as the amperage rating goes up. I haven't researched it, but my assumption is that it's a safety thing with the intent that you can't fit a higher amp fuse into a spot where a lower one belongs because the body will be too long. So what's the point? The point is that I thought all the Z fuses were the same length, and if they're using the SFE series, then they will all be different lengths. At 20A, the SFE series and the AGC series are the same length meaning that an SFE20 and an AGC20 are the same length. And the AGC series doesn't do the same thing with the lengths that the SFE series does. An AGC20 is the same length as an AGC10.

I haven't made any reservations yet, but I'm intending to make it. Hoping to have my car there as well, although I'm not planning to enter it into any of the show portion. I hope we can get a gaggle together of people like we did in Memphis. That was a great time.