Captain Obvious

Haha! So in other words, pretty much exactly the same kind of stuff that always happens. Good luck with the rest and hope you get done in time for Memphis!!

Gotcha! I'm not hung up on an exact match color wise, but how do you think that Dupli-Color Ford blue compares to the original blue?

Honestly, I don't even know what to say... http://newyork.craigslist.org/stn/cto/5112085516.html

You are clearly certifiable. BTW - Superlen had characterized a couple AFM's on his flow bench...

So your color target was Bud Light Blue?

Little bastard shot me right in the arse.

Gotcha on the check valve. So the brakes worked fine for some time before they started to tighten up? That's odd... Makes me think there might be something wrong with the check valve in the master cylinder. Are you sure it's both front corners and not just one side? I'm no expert, but I wouldn't expect it to be a mechanical issue with the pad pins. Problems with those could cause a little drag, but I don't think they would cause enough of a problem that you would notice it in the car being dragged down. I would also consider it unlikely that both rubber hoses collapsed inside at the same time. They do go bad, but both sides at the exact same time? Master cylinder check valve? Rebuilt caliper(s) that sat on the shelf so long that the pistons corroded up again? Good luck with the investigation.

Whaaaaaaaaat??

Took me a page and a half of scribbled op-amp circuits to catch up to you (and I think there are some surmountable resistor value related errors in the design), but I got it. Neat use of active positive feedback. I won't guarantee that it would actually be as linear as expected without bread boarding it, but it certainly looks promising. Your kung-fu is strong. I reiterate however, that I think you're loony for even thinking about such ventures... The original Bosch design is a highly characterized black box of analog voodoo that cost probably hundreds of thousands of 1970's dollars to develop, took thousands of man hours, and several design iterations before they even had anything that would start and run under all input conditions. That said, I'll do whatever I can to help. Haha!

TomoHawk, Not sure what you're asking... What do you mean with the above? I'm probably just dense, but can you ask your question a different way?

Look up tables aren't analog.

The reason I brought up the integrating ADC is because it uses the concept of a linear ramp to a threshold and also uses analog switching to change around the input circuitry. I wasn't saying it would be a drop in for anything here, but a lot of what you suggested is "reminiscent". I didn't mean it was a solution, I just meant that it has a lot of the same trappings inside. As for your sketch... I don't see anything on there anywhere that would result in anything except steady state DC voltages. I think your little graph in the lower right that shows a linear ramping voltage is creative license that I don't think would occur. If you want a linear ramp generated from a DC voltage, you have to integrate the area under the DC line over time. You need an integrator and I don't see one anywhere. No bad vibes intended, but I think the output of every op-amp in that sketch would be flat-line. Yes, I went there. Boating, Miatas, football, Sandy Bottom Nature Park, Plum Tree Island Reserve.

I have no direct experience with the brake check valve, but there is a parameter of any check valve called "cracking pressure" and it's the differential pressure required to "crack" the valve open and allow flow. Because of stiction in the sealing surfaces inside, they are never completely smooth and that thump you feel and hear is probably the "crack". As for your calipers sticking... The check valve is a red herring. The brake booster will always have vacuum present in it even when the engine is off. I'm no expert, but I've heard it's a federal safety requirement to allow for continued brake power even in the event of a motor stall. You get like two good pushes before the vacuum in the booster is gone. So I don't know exactly how the check valve should sound, but I can tell you that it has nothing to do with your calipers sticking.

Not my fault....

Does anyone else have these sorts of troubled thoughts? Well I'm sure you're not surprised to hear that I do, but my advice to you would be... Think about something else. Maybe boating. What you described is reminiscent to an integrating A/D. You ever mess with one of them? It's similar except you're proposing a variable threshold instead of a fixed reference voltage. Something else... Maybe sports?

Yes. the stock 260 distributor has a vacuum controlled mechanical advance feature.

I'm there too. I don't know when I started paying attention to the details, but I see a lot more now than I used to. You'd have a field day with my car.

Me too!

Are you the older one or the younger one?

Namerow, Forgot to ask... Does this plug-n-play diagram agree with what you were intending to construct? Other than the early pigtails using a black wire between the main harness and the bulb prongs, does everything look right and make sense?

Yup. That's the same thing I've found as well. Thanks for checking. So somewhere along the way they changed some of the wire gauges sizes and the color of the common connection wire (from black to red), but I don't think the pigtails ever used "side specific" wiring colors.

Depends on the year of 280... 77/78 are different than previous years. An easy way to tell the difference is that the 77/78 have an angled front mount and flat rear mount while all the previous years had flat mounts on all four corners. I believe the change occurred at the same time as the different doors. They changed a lot of sheet metal at that time and I believe it was all part of the same upgrade. So I believe the bottom line is that you could use 280 mounts in your 240 or 260 as long as they are from 1975 or 76.

Excellent. Thanks for the pic and the tip to that one on Amazon.

TomoHawk, Thanks for the wiring diagram. If you get a chance to look at your pigtails, let us know. Namerow, That's another change they made in later years. The 77/78 connectors between the engine bay harness and the pigtails is different than previous years and not all of the contacts are the same size. At the bulb end, mine are all the same size, but at the harness end, the R/W (high beam) is larger than the other two. Doesn't really make electrical sense and I would have told them there's no benefit, but I wasn't there when they designed it.

The 77/78 pigtails kept the same wire gauges all the way to the bulbs which makes more sense electrically. In theory, they could cut the gauges on the pigtails some because each side only carries current from one bulb instead of two, but they kept them all the same. I've seen that printing on the back of the headlight connectors as well. Makes me think that at one point the plan was to run the headlights with the common connection to ground. I doubt Nissan molded their own connector shells, but the people who made them were thinking that common to ground was the intent.