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Captain Obvious

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Captain Obvious last won the day on August 6

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About Captain Obvious

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  1. Captain Obvious

    Brake booster testing

    Woof. No fun at all. Here's hoping for a speedy recovery! Have they got PT in your future?
  2. Captain Obvious

    76 Datsun 280z throttle sticking

    To each his own then. Haha! My fuel pump and AFM are working great. You're the one that that refreshed this antique post about a sticky throttle body. My throttle body was only sticky when the engine was warm and only when it was running. So needless to say that mine unfortunately mine wasn't as simple as the carpet being bunched up. I also disassembled this part and made a new spherical bearing for inside. That took a lot the slop out of the linkage, but it didn't do anything to fix the sticky idle. Problem was in the throttle body itself.
  3. Captain Obvious

    Datsun-240z Vs Fairlady-z432

    The type of cap that really belongs on the radiator depends on whether the plastic overflow container in intended to be a pressure vessel or not. Based on the domed end shape and the thick walls of the plastic container you have, it looks like it may be capable of holding the system pressure, but the plastic cap you have on the tank looks like it has a small vent hole in the center: So if that is really a vent hole in the plastic cap (and it is the correct cap for the plastic container), then you should be using a radiator cap like the ones you pictured before: In other words... Somewhere in the system, you need to contain the pressure up to the rating of a cap (for example) 13 psi. And if you're not containing that pressure with a spring loaded radiator cap, then you need to do it at the plastic tank. But you would need a sealed cap there that included a pressure relief. I'm resisting describing how a typical system is supposed to work because I'm sure you already know all that and I don't want to explain a whole bunch of stuff you know already. But if you want, I can whip up some sketches, etc. to try to describe that.
  4. Captain Obvious

    76 Datsun 280z throttle sticking

    Not to worry. The Sentra throttle body has not only the same mounting bolt hole locations as the original, but also has the identical throttle plate diameter. So no performance upgrade to "worry" about there. So... Since the throat bore and throttle plate is the same as stock, then one might ask "So why would you go through all that trouble to switch?" Valid question. Answer - Because it has roller bearings and built in vacuum seals on the throttle shaft. Smooth as silk and absolutely no leaks. That's why!
  5. Captain Obvious

    76 Datsun 280z throttle sticking

    The throttle body I've been working with is (basically) from a 96-98 Sentra. There are some differences between the beginning and end of that range. Most noticeably the inclusion or lack of a vacuum port for the distributor advance. The earlier ones (96) have the port, but they stopped using the port in 97. Presumably digitally controlled instead of vacuum starting in 97. It's not a direct drop-in swap, but it's manageable. I had to make some customizations, but here's a teaser: One thing to note on the above pic is the green spring in the lower left of the Sentra throttle body. That spring is part of a system that boosts the idle when cold by acting on the throttle linkage. It's essentially the same function performed by the AAR system on the 280Z. Using the throttle body above allowed me to completely remove the AAR system and all it's associated plumbing while still having a boosted idle when the engine was cold. The tradeoff is that you have to plumb the new throttle body with coolant to heat up the built-in thermostat. If you don't mind keeping the original AAR idle boosting system, then here's another option... I didn't buy one and dissect it in my shop, but just from analyzing at the yard, I believe the throttle body from an earlier Sentra would be a pretty easy adaption as well. This is from 94, but I don't know the year range. It's simpler than the 96-98 version as it does not have the temperature controlled idle boost incorporated into the linkage. I chose the 96-98 version because the temperature controlled idle boost allowed me to get rid of the whole AAR system and still have a boosted cold idle. Note that this one has the vacuum port connection for the distributor:
  6. Captain Obvious

    Datsun-240z Vs Fairlady-z432

    Kats, I haven't been able to follow the part numbers, but all three of these caps appear to have the check valve which allows coolant to flow back into the radiator from the overflow can when the engine cools off and draws a vacuum. I'm not sure it will add anything to the discussion, but I did a little radiator cap repair work on my 280. Here's a pic of the cap disassembled. The inside (usually hidden side) if the check valve is in the upper left corner:
  7. Captain Obvious

    Brake booster testing

    If they won't hold vacuum (even with the M/C hole sealed off), then there is probably an internal leak. Hole in the diaphragm or the poppet valve seal is leaking. If that's the case, when you try to draw a vacuum on it (or in your case... pull air through it), you should be able to hear air entering in the assy at the pedal push rod. Through the little felt filter thingie. Other possibility of not being able to hold a vacuum is that it's leaking at the seam between the two sections of the clamshell where the diaphragm is pinched, but you don't hear much about that happening. it's usually something internal. Please make sure you let us know what you turn up for rebuild options and/or parts!
  8. Captain Obvious

    Is my coilover spring rate too high?

    The FSMs says the following for the 280Z (75 - 78): Front springs for 75-78 two seater - 1.84 kg/mm or 103.0 lb/in Front springs for 75-78 2+2 - 2.06 kg/mm or 115.4 lb/in Rear springs for 75-78 (both 2 seater and 2+2) - 2.28 kg/mm or 127.7 lb/in So it appears there is a difference between front and rear as the rears are about 25% stiffer. Of course I've never measured any of that for confirmation or accuracy, but that's what the documentation indicates.
  9. Captain Obvious

    Brake booster testing

    I connected mine up to my vacuum pump. Used a little valve cracked a little as a regulator so I didn't suck the booster down to absolute zero. You don't have to blank off the master cylinder port. The rubber vacuum seal on the output shaft should keep the vacuum in the clamshell.
  10. Captain Obvious

    Idle problems.

    Yup. All at the same time. Plug everything you really don't need and try to isolate the issue.
  11. Captain Obvious

    Idle problems.

    I'm in agreement with the theory of vacuum leak(s). Your vacuum at idle should be well into the double digits. Hopefully 15 in Hg or higher. I'm also in agreement that simplifying the system to try to isolate the leak is a good idea. Pull and plug the brake booster. Pull and plug the EGR system. Pull and plug the HVAC system. Pull and plug the carbon canister system. Carefully inspect the PCV tube on the underside of the intake manifold.
  12. Captain Obvious

    Stamped numbers on steering shaft

    I've got a couple steering shafts around here from different years. I never looked for numbers on them, but will do so when I get the chance. Maybe a couple more data points for a shaky theory.
  13. Captain Obvious

    Is my coilover spring rate too high?

    I took a look a one year further back in the manuals, and the spring numbers are all over the place. The 74 manual even seems to indicate that the front left and front right springs were different. Do people really believe that to truly to be the case? The fische has all sorts of numbers and left and right are different! All I can say is that I'm glad they got that all sorted out by the time they got to the 280!
  14. Captain Obvious

    Stalling issue(under throttle)

    I couldn't get the video to load. Can you put it on youtube?
  15. Captain Obvious

    Replacing S30 Rear Wheel Bearings

    Without having the parts here to inspect, I'm kinda at a loss to come up with ideas. If everything measures properly and everything is seated properly, then it should work, right? I modified a pair of calipers so I could make a direct measurement on the distance between the two bearing seating surfaces. Here's a pic showing that direct measurement: And here's a pic of some distortion that can cause problems. This is what happens when you try to press a bearing in at an angle. You can see the semi-circular mark on the far side where they gouged the cylinder wall that is supposed to locate the bearing. That raised bump was pushing the bearing to one side and not letting it seat square:
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