Captain Obvious

Yup. That's why I bought one. I was working on a 74 at the time. But..... They were wrong. It wasn't for 73/74, it's for earlier. And the needles are wrong for any year.

I surely won't claim to have seen them all, but every carb cleaner I've ever run across is highly flammable. I'm not talking about the engine degreasers... I'm talking carb cleaner. Mostly acetone, methanol, tolulene, etc. And for the shaft leakage... As designed without a pliable seal there, some leakage will naturally occurr. But as long as it's not "excessive" you don't have to do anything about it. There's others on the forum with much more carb experience than myself, but my read on it would be if you can tune the carbs at idle without having to go some unusual amount of turns down on your nozzles, your plugs look good, and you're getting good power while driving, then I wouldn't worry much about the throttle shafts sealing.

I thought the expectation when you sprayed carb cleaner near a vacuum leak was that the idle would go up, not down?? And I would guess that vacuum leaks around the throttle shafts wouldn't have much of an impact at highway throttle positions. I would expect that even if you were getting some air past the throttle shafts, it might have a big impact on IDLE, but once you cracked the throttle plate enough to maintain highway speeds, the impact of that leak would diminish. I mean, you never WANT that leak, but it's impact goes down as the throttle position goes up. A little late now (as you already figured out), but I don't think leaking throttle shafts are making you run hot on the highway.

I believe they used SU's on some of the Volvos, so if he's got old Volvo experience, he should know his way around the Z carbs. Only question though would be is he capable of making the leap from the round tops to the flat tops like what you have... They are the same carb in theory of operation, but there are a few differences. That list I put together was assembled with an attempt at "all things considered". By that, I mean, I tried to put together a list of things that wouldn't cost much, wouldn't be very difficult or require special tools or equipment, and wouldn't take too much time at any one sitting so you could still use the car as your DD while working on it. My intention was not only to get you some possible improvements in how well the car worked, but also an expectation that you would get some experience and knowledge while doing that work. You could spend hours and hours and hours on making things perfect, but I know it's probably not the right time for that. Once you know your way around the car and have a handle on the FSM, you get to spend countless hours working on everything else! If it's running well once warm, isn't billowing black clouds, and has decent power, then you're doing as well as a lot of Z owners. Haha! It's amazing to think how "spoiled" we are with todays cars... You get in, turn the key, and hit the road. I typically start the car cold in the morning, and have wheels turning no more than ten seconds after the starter has stopped spinning. No muss, no fuss... It just starts and goes. We take it for granted now, but when you think about it, it's really amazing!

Apologies ahead of time if I'm wrong, but I'm gonna go out on a limb and make some age related assumptions. I don't know how old you are, but I'm guessing that every car you have ever seen or been in to this point had computer controlled fuel injection systems and no choke. You got in - turned the key - and went off down the road without a hiccup. Well let me tell how it used to be in the old days... There was no electronic fuel injection or computers of any kind in cars. Cars had carburetors and chokes. When you first started your cold carbureted car, it ran "OK" if you were lucky, and "poorly" if you weren't. If you were lucky, you could let it sit at high idle for a minute or so to warm up before you went off down the road, and if you weren't lucky, you had to sit there for a minute and nurse it to keep it running. Then once it was running well enough that you felt confident that you could pull out into traffic without stalling in front of someone, you could get moving on your way. As you put a few miles behind you and the engine continued to warm up, it gradually got better and better until it ran "good". The best you could ever hope for was that it started easy, idled smooth but tentative while cold, and improved quickly to the point where you were safe to leave your parking spot. So what would I do? With the FSM as a guide, I would start with the easy stuff: Ignition - Install new distributor cap, rotor, plug wires, and spark plugs. While you're in the distributor, check your ignition pickup gap. Once you have installed new components and verified your pickup gap, check your ignition timing and adjust as necessary. Fuel - Check and adjust your damper oil as necessary (yes, you have a fill-to line on the damper stalk). Check your float bowl levels. I would assume that if your float bowl levels are OK at idle and you aren't running out of power on the highway that your fuel filters are not clogged (yet). Air - Replace the air filter and inspect all the vacuum hoses and lines in the bundle of snakes and compare against FSM for correct locations of all the tubing. Vacuum leaks are not your friend, and because of the complexity of the 260's system, there's lots of opportunity for them to occur. Keep in mind that this is just the simple non-invasive stuff. Beyond that are more invasive tasks like setting the valve clearances and replacing the fuel filters. Also keep in mind that I'm focusing on simple "performance" based stuff, and there is a lot of "safety" related stuff suggested earlier by SteveJ and LeonV like brakes and suspension inspections. Keep us posted!

Problem is that you've got no "baseline". You don't have any portion of the car verified, tested, proved positive, that you can be completely confident is working as designed. What I mean by that is, for example... Stuff like a short lived dead spot, "bogging" on heavy acceleration as you described above could be caused by a whole bunch of things. Some carb related, some not. Could be anything from lack of oil in the carb dampers, to a clogged fuel filter back in the electric pump, to a distributer problem. Might be fuel related, might be ignition related, might be air related. Could be anything. Point is, either you better get good at opening your wallet, or you better get good at finding and fixing your own issues. So back to the carbs... The flat tops work great when they're working great. I'll even risk poking the hornets nest here and go out on a limb to claim "Better even that the round tops." Problem is, as with many other "better" systems, that improvement comes with the down side of complexity, and that complexity provides more avenues for problems to work thier way into the system. The bottom line is, either carb choice works great if done properly, but the round top system is boatloads simpler than the flat top system. That simplicity makes it much easier to keep the round tops working properly and also to troubleshoot problems when they do occur. I know the flat tops pretty well. But reaching that point is much easier to achieve if you aren't behind the eight ball working on your daily driver!

Speaking of EGR, one of the things that can cause the problems you're describing is if your EGR valve is active when it shouldn't be. The EGR valve should only be open after the engine has warmed up, and if it opens before that, it can cause rough running. To check for that, pull and cap the hose running to the EGR valve (the thing with the large round cap) and see what happens.

Your cold start and running issues don't surprise me at all: "In 08/11/08 it had all the hoses replaced, repaired the choke and cleaned out the carbs and had 83,520. I bought it with 83,760 on Friday." Sounds to me like the previous owner was chasing a performance problem with the car... He had all the hoses replaced and the carbs taken apart and cleaned out four years ago, and then put less than 250 miles on it since. I assume it's been sitting with the same gas in it for those four years? I'd be happy that it runs at all! If you're looking for significantly better performance that what you're getting now, you're probably going to have to get inside the carbs. Or open your wallet and find someone near you who's got a handle on the infamous flat tops and hope that it's something simple that can be addressed by the anemic rebuild kits. If you were closer to me, I'd be happy to help you with them, but I'm several hours from you. Also, from one of your previous posts, there's a question that hasn't been addressed: Under that cap is your EGR valve. I'll second the guess that you've got an exhaust leak. Probably at the rear of the engine back by the firewall.

I took apart a reservoir tube from a flat top and verified that it is made up of multiple pieces. Unfortunately, I don't have a round top piston that I'm willing to autopsy, so I cannot definitively say that the round tops are multiple pieces as well, but after seeing how they did the flat tops, I bet that the round tops are multiple pieces too. I can now theorize possible fluid loss through the seams between multiple pieces plugging the bottom of the reservoir tube. So, if you are in fact losing oil and it's not your imagination, that may be where it's going? Here's some pics of what I did. Flat top piston on left, round top on right: Bottom of flat top. You can clearly see the seam line between multiple pieces: Bottom of round top. There is no seam, but the diameter is smaller than the OD of the tube. In fact, it is the same as the ID: A few seconds on the arbor press, and the flat top tube is out and apart: Anyone have a beyond help round top piston that they want to donate to the cause?

Auto or manual trans? If it's an auto trans, maybe your advanced points are OK, but your retarded points have a problem? Runs OK at first, but as soon as it warms up and switches to the retarded set of points, it dies?

Forgot about this part... I'm not really sure what problem you're identifying with the above, but I'll take a guess. if you're trying to figure out why you're seeing too much shoulder when you use the "leave the lock screw a little loose and push the piston down onto the jet" to establish the needle position, it's because you've got the mixture screws turned down a few turns to where they should be to have the car idle properly. Those two or three turns down on the mixture nuts will hold the nozzle jet down and that will add to the length of exposed shoulder when you use the "loose lock screw" method because you're using the nozzle to push the needle into the piston. The more turns on the mixture nuts, the farther down the jets, and the more shoulder you will end up having exposed. Is that maybe what you're talking about?

Foot in mouth, I just checked, and I don't have the 71 manual. Oldest I have is 72, but the needle setting procedure is the same. With that in mind, I've included page EF-28 (Engine Fuel) of the 72 manual below. A little hard to tell from the blurry scanned pic, but you should use a straight edge to set the shoulder of the needle even with the bottom flat face of the needle. Don't set it to the depth of the narrow groove in the center of the piston face. Set it to the large bottom-most portion of the needle. In other words, If you pull the needle out of the piston completely, and then set the piston needle hole side down on a flat table... The surface that contacts the table is the surface you should use to locate the needle shoulder. If done correctly, you should be able to see a small portion of the needle shoulder sticking out of the bottom of the piston when you're done.

The factory manual says you should use the straight edge along the bottom face of the piston to locate the shoulder of the needle. The shoulder should not be higher than the bottom of the piston... It should be perfectly even with it. If you post what year are you working on, I can point you to the correct page in the manual.

You're right about universal mysteries. I'm not quite ready to give up on this one though. Not until I cut one open. :ogre: I've seen that same note in the FSM about checking the damper oil, and I agree about the implication. I'm thinking that it's just prudent to check it every now and again. Shouldn't have to add any, but still prudent just to check? Perhaps oils in the past were a little more volatile than they are now? Maybe there's a tiny bit of evaporation when hot, and maybe that evaporation used to be more prevalent in the past with less sophisticated additives? Just musing ideas...

Greg, From what I've seen, your bar sounds unfortunately typical. I sent you PM.

A lot of people complain about the 260 carbs. They are commonly known as "flat tops" because of the shape, and most people don't like them. Parts availability for the flat tops is difficult. You can get a "rebuild kit" easy, but if that doesn't fix the problem, then you're out of luck. The support structure just isn't there to supply other parts if necessary. If it's running fine, then don't poke that nest. However, if you have carb problems, unless you find someone in your area that is willing to work on the "flat top" 260 carbs, then you may have to switch to the older "round top" 240 carbs used from 70 through 72.

Yes, if you reach resolution, I'd love to hear it. I've still been thinking about it, and I took a good look at the damper tube under bright light and magnification. I didn't see anything that would contradict what we've already covered. The cavity is dead ended at the bottom, and what's happening to you should only be able to occurr through the top. What I was thinking I might find was that the damper tube wasn't one piece, but instead was made from multiple parts pressed together at the factory. My thinking was that any seams could potentially allow for a low end leak. I didn't design the thing, but for ease of manufacturing, I would have done it with multiple pieces. Much easier than creating a highly polished, deep, blind ended hole with a square face at the bottom. I would have started with tubing, already highly polished ID and OD, and pressed a plug into the bottom end that had been machined to accept the needle. However even under light and mag, I found no evidence of that. It's possible to have been designed in such a way that there are no visible seams, but I wouldn't know for sure unless I destructively disassembled one. I've got a parts carb, so I may do just that, but it won't be for at least a week. If there are multiple parts, it would open up a whole new family of explanations and solutions. BTW - This won't help any, but here's the other thread I was thinking about where there was a guy saying that he kept losing damper oil. As far as I know, he never reached resolution either: http://www.classiczcars.com/forums/thread43034.html

Yes, your understanding and description are correct. The tube is blind ended at the bottom and the only opening into that cavity is by way of the hole at the top. So barring defect or damage, the only way into or out of that reservoir is from above. I can picture three ways to get oil out of that blind cavity. 1) Evaporation - Which should not be happening to 20W motor oil 2) Check valve not passing fluid fast enough on the downstroke and lifting oil up and over the top of the walls - Which you tested 3) A crack or other passageway near the bottom of the tube that shouldn't be there - Very unlikely to be identical on both carbs I have seen motor oil "migrate" from one location to another, but it happens very slowly. If you take a metal soup can and fill it halfway with oil and put it on the shelf for a year, I swear that the outside of the can will be oily. Your issue is happening much too quickly for that though. I must be missing something...

I like that. So how are those attached? Is there a thread here somewhere where you talked about this install?

Pics when you're done?

Stalks out piston lifts easily and falls quickly is perfect. Stalks in piston has resistance lifting and fall is only slightly damped is also perfect. Not exactly sure I understand what you meant by not seeing spillage, but if you lift and drop the pistons without the stalks installed, you aren't testing anything. You won't cause any spillage or overflowing doing that. You need to have the stalks installed to do the lift and drop test. c1) Pull the stalks out and make sure the reservoir is filled to the correct level c2) After verifying that the oil is at the proper level, reinstall the stalks in their normal operating position c3) Stick a finger in the mouth of the carb and lift the piston all the way to the top until it won't go any higher - Should be hard to lift c4) Let the piston drop as fast as gravity and it's spring will allow - Should fall quickly c5) Repeat c3 and c4 ten times c6) Pull the stalks out and check to see if the oil level has changed. If the level has changed, there should also be fresh oil on the outside of the reservoir tube. If the level has changed and there's oil everywhere, make sure that all the brass jiggly bits are clean and goober free and everything that is supposed to move does. The top washer is fixed to the shaft (as is the C-clip obviously). The lower washer and the cylinder should jiggle. Also check the stalks? Do they appear straight? If you lay the stalks tits up on the bench, are the shafts perpendicular to the benchtop? One last question that I should have asked a while ago... Do you know if the engine has to be running in order to consume the oil? By that, I mean, how many days does it typically take you to accumulate 350-400 miles? And if you would happen to let your car sit parked for that same length of time, would the level change, or does the engine have to be running to cause the disappearing oil?

You don't want back pressure. You want momentum. Problem is that sometimes an increase in momentum is accompanied by an increase in back pressure. I'm no expert in the field, but my theory is that since an increase in momentum is often accompanied by an increase in back pressure, people started thinking that back pressure was the desired effect, and it's not. It's the unwanted, but often necessary, side effect.

Sorry... Meant to say there are two washers on the top and a C-clip on the bottom and the jiggly cylinder between them. Dropped some words by accident. I also wanted to explain the purpose behind the lift and drop test. You should be able to lift the suction piston all the way to the top until it won't go any further and then let it drop full speed to the bottom without any fluid loss. If the check valve is working properly and the oil is of suitable viscosity and level, then it should rush through the check valve fast enough that it won't pool on top of the valve enough to lift the oil to the point where it can escape out the top of the tube. If, for whatever reason (for example... too thick of an oil viscosity or something wrong with the check valves), the oil does not flow through the check valve freely enough when the piston is dropping, then you run the risk of lifting oil up and out of the tubes. Does that make sense?

Bummer. I was hoping that this was a non-problem and you were simply overfilling the tubes. It's been a while, but I remember someone else had a problem with dropping level in the dampers, but I don't remember if they ever reached resolution. I'll take a look for that thread when I get a chance. Take a look at the jiggly bits. There are two washers on the top and bottom and the jiggly cylinder between them. The washers are different between top and bottom, and if memory serves, the cylinder may be as well. It's unlikely that someone took them apart and mixed up the parts, but if your oil isn't seeping out the bottom and isn't evaporating into the air, then it has to be coming back out the top of the tube somehow. Here's some far fetched ideas... Maybe you have a crack in your suction piston near the bottom that is allowing oil to seep out? Maybe the piston was machined incorrectly and what is supposed to be a blind hole isn't and there's some passageway through to the top of the needle? And yeah, if you find any O-rings in there, definitely take some pics and call an audible!

I wasn't expecting that the jiggly bits wore out. While that is possible, I consider it very unlikely. I consider it much more likely that there's a goober in there affecting operation. Or the stalks are bent or misaligned. Or a previous owner took the check valves apart and got them back together incorrectly. Or hopefully... There really isn't any problem at all and the OP is simply overfilling the tubes all the way to the top and expecting them to stay that way. So, back to you Jetaway... What is it that makes you think you need to add oil? When you say: Are you filling the reservoir to the very top and then putting in the stalks, or are you filling the reservoir a little and then using the stalks as dipsticks until the level hits the fill-to line on the stalks? It takes a surprisingly small amount of oil to do this. The reason I ask is because if you are filling them to the very top before you put the stalks in, then you are overfilling the dampers. Won't hurt anything as the excess will simply be pulled into the cylinders and burned, but if that's the reason you think you have to keep refilling them, then what you've got here is a non-problem.