LeonV

If the car was sitting for a long time, there is a good chance that the seals in your master (and probably slave) have dried up and no longer work properly. I'd replace/rebuild the master along with the slave. Do the same for the brake system.

Bingo, that's exactly what I'm getting at! That radiused plate will diminish entrance losses to the carb, as good as or better than an air horn (depending on air horn geometry). You can use filters that fit and flow with the benefit of a radiused entrance! That's exactly the thoughts I'm trying to avoid. As I've said, the air is already turbulent, regardless of having a horn or not. There will be more entrance losses without a horn but fuel metering will be unaffected, for all intents and purposes. I've had no problem at all with fuel metering when running SUs without horns, along with many others who have done the same (as Mortensen mentioned and Healey realized). Again, an air horn will be beneficial for performance, but because it decreases entrance losses and increases powerband bandwidth. That's it, that's what it does.

I don't think anything was confusing, and if it is, then I didn't see anyone (but you) chime in about it. I have no problem clarifying any statements that are not well understood. I'm not arguing completeness, I'm just pointing out that what you said is wrong. No, that is incorrect, again. The air flow is not made less turbulent! A rounded inlet decreases flow separation (the vena contracta which you mentioned), not turbulence. If the air flow was made less turbulent then flow separation will be more likely (bad). Even if it did make the airflow a little less turbulent, does that have any effect on engine operation? Nope. Air flow in the intake will always be turbulent, and you really want it to stay that way for fuel atomization purposes. Also, air horns do not directly increase intake velocity, they increase intake pressure. It is not an intake velocity discussion. Intake velocity is another internet term (like backpressure) that is thrown around all the time with disregard to what it really affects... Look, you can say what you want and maybe you were inferring something completely different than what your post seems to say, but such a vague statement like "smooths out airflow" is not nearly describing the actual function of the air horn. Shouldn't someone know what the part does before deciding whether to ditch it or not? All I'm saying is that someone with the right knowledge will be able to make an educated decision. Others will grasp at straws. If the decision in Healey's case involves air horns vs. better filtration, then I think the proper decision is the one that gets you the most torque, power, volumetric efficiency, whatever you want to call it. In his case, it could be a wash and going either way doesn't change things much, whether he uses an air horn with a restrictive filter or no air horn with a less restrictive filter. The gains and losses may cancel each other out, and nothing noticeable happens. So no, he clearly doesn't need an air horn to have a great running car, as he seems to have already found out! I guess by your logic, if you want you L-series to run as Nissan intended, then you really NEED to be running an air pump and stock exhaust too.

Well there you go!

What you're talking about is entrance losses, as I mentioned. I try to give the kind of information that will educate someone as to why something happens, instead of telling them "SUs need air horns". I think the proper knowledge in fact does help his situation! I prefer cause and effect to groupthink reasoning. This is your quote (bold for emphasis): What you said was incorrect, so I corrected it in order to not perpetuate further myths. SUs will work just fine without air horns, or any carb/intake for that matter. It is clear though that air horns do improve performance, but for the reasons previously mentioned. I'm glad someone appreciates it! They will make a difference. I don't know how noticeable the difference will be but it's enough to show up on a dyno. I just don't like the term "smoothing airflow". It's one of those internet/old mechanic's terms, like "backpressure". It's not what the airhorn does, and I'll leave it at that. I completely agree with your point about the filters, Jon, and I don't think that one would come to that conclusion if they thought that SUs need an air horn for "proper function". This is where understanding how the part functions helps make the proper decisions.

Air horns have absolutely nothing to do with making the airflow "smoother". What the air horn does do is increase the overall intake length as well as reflect harmonic pressure waves in the intake over a larger rpm range. A longer intake length shifts the torque curve down (moves toward midrange) and the shape of the air horn will dictate the "bandwidth" of the intake's tuned length (width of torque peak). Air horns are definitely beneficial, it just has nothing to do with "smoothing" out airflow. The air horn will also slightly decrease entrance losses since the SU's mouth is squared off, however, any radiused feature at the carb throat entrance will help that.

Both the R180 and R200 diffs have flange connections to half-shafts (driveshafts in Nissan-speak). Thus, 240Z half-shafts can be used with the R200. They are not the difference. The biggest difference between the R180 and R200 are the physical size (180mm ring gear vs. 200mm ring gear).

My reply was poorly phrased, but looks like it's already locked from editing... In a nutshell, exhaust flow is not only turbulent at the boundary, but is so everywhere else. If you would have said "friction" instead of "turbulence" in your post, then that would make sense. Otherwise, mentioning "turbulence along the boundary" doesn't make any sense.

The engine number on the block is located by the starter, and a plate with the matching number should be in the engine bay. You are correct that a 5-speed never came on a '76 280Z, they started being offered as an option in '77. There is no way to match any numbers of the transmission to the car but we know that a 5-speed was not available in '76, therefore it is not original. Search around and you should find info on identifying different transmissions, usually by the "ears" (exhaust hangers) at the rear of the transmission. With that said, it doesn't really matter if it's numbers matching or not. I don't see that adding much value, especially on a '76 2+2. If the engine and trans are in good shape, there is no reason to toss it aside just because it isn't matching. Conversely, even if engine numbers match, that doesn't mean that all of a sudden a '76 2+2 is worth $1000 more.

I don't know about you, but I don't think putting in a 3.9 R200 was a waste of money in my (non-V8) Z. Many others install the R200 in order to change overall gear ratio, along with the added strength. Aalthough you can find R180 diffs with similar ratios, they are tougher to come by. I don't see any problem with having an R200 in an L-powered Z, it just didn't come from the factory that way.

Flow losses do have something to do with surface area, but not with some sort of boundary turbulence. Flow actually tends to be stationary at the boundary layer, if there is one. Exhaust flow is turbulent, thus there is no boundary layer and turbulence exists everywhere inside the pipe, not just the surface. But this is a tangent to this topic... Frictional losses go up with surface area, so twice pipes with an equivalent total cross-sectional area to a single pipe will suffer more losses. How much more? I have not quantified this with calculations or testing yet, so I don't know how strong the effect will be. Be aware that the inherent differences in design between a single and dual system also have an effect on engine performance.

The R200 was put into US Z-cars starting with the 260Z 2+2, continuing on to the 280Z and so forth. The 240Z never got an R200 from the factory.

Right, I understand that, but dropping the pump and distributor is a bit overkill IMO. If you can get the job done without doing so, I don't see a problem with it. Only if the problem lies in a broken gear or spindle would I drop the pump and dizzy. Otherwise, it's as easy as finding TDC, setting #1 plug wire to where the rotor points, putting the rest of the wires in the right order, checking with a timing gun and you're done!

It is an easy job IMO, on a carbed car at least. Use patience (and lots of rust penetrant) while loosening the nuts/bolts. Loosen from outside to inside and a little bit at a time. Break loose and slightly re-tighten all fasteners before removing any. I do this to ensure that each fastener is removable before actually taking them out, and so that all fasteners are sharing the grip load instead of the final one taking all of it while you're trying to remove it. Remember that some fasteners share intake and exhaust flanges. Make sure to get new intake/exhaust manifold studs, they're $20 or so from MSA. I've done this a few times and can do the job in an hour or less, unless some nuts are stubborn. It helps to have a spare head on the workbench to reference bolt hole positions! Don't forget to disconnect throttle linkage, heat shield and the fuel rail as well. When reinstalling, use antiseize on the studs and thread them in. Use the studs as a gasket-guide. Make sure to tighen in sequence from inside to outside. Do not overtighten, I believe only 10-15 ft-lb is called for.

...and me too. I'll second that as well!

You don't need to take the pump or distributor out, and you don't even have to pull the valve cover if you don't feel like it. Pull the #1 plug out, disconnect the coil wire, put your thumb over the plug hole and stop when you feel the compression stroke (you'll feel it). Mark (or memorize) where the #1 plug wire is on the distributor cap and take it off. Look to see if the rotor is pointing there. If not, adjust the plug wires on the cap so it is, and make sure the firing order is correct. If you're going to check valves, the valve cover will come off anyway which makes visual inspection of the cam the preferred option.

I recently had a slave fail on me and replaced just the slave. Just make sure to inspect the master and you'll be fine. Unless failure is catastrophic, you'll feel clutch hydraulics being to fail before they completely die. Lower clutch engagement is a telltale sign. At least that has been my experience, YMMV.

Again, how did you quantify better response? Something may feel different but not necessarily be different. The airbox lies upstream of the throttle plate. If the airboxes were truly very restrictive, as you say, then you would see a power increase over the entire powerband because of decreased pumping losses. Throttle response, which people seem to love to talk about, is a seemingly subjective subject which is ultimately dictated by the volume between the throttle plate and intake valve, and definitely not before the throttle. But this is getting to be a didactic digression. I seem to be all about alliterations today.

There is no "resonator" and how did you quantify "better throttle response"?

What you must realize is that the advertised flow rate is usually "free flow", meaning zero pressure (no load). If you look at a pump curve, you will see that flow rate decreases as pressure rises. In reality, you will never see 32gph out of that pump. I have not done pump sizing calculations for my Z (L24 with triple DCOE), but having extra flow is better than too little.

Nice 260Z! You definitely don't see many complete and stock ones like that. I have an early 260Z as well (RLS30-004406). I enjoy their "rarity" and quirkiness as they have a lot of things that are 260Z-only. Enjoy!

First, bleed the master if you haven't already done so. Second, search "reaction disk" if bleeding the master doesn't work.

I second that. From all the drum brakes I've worked on (mostly old domestic cars), S30 drum brakes are the easiest to work with. Doing the rear drums on a Z is an easy job, the only thing that can make it difficult is rust and that's what gratuitous use of penetrating oil is for!

I'm betting it's from the original fuel pump circuit...