Zed Head

Was the suspect valve on the base circle? You should read up a little on how to adjust valves. You might have just opened that valve up and are in the process of burning/warping it or it's so far open you've lost a cylinder (no compression). The proper valve adjustment process is described in the Engine Tuneup chapter of the FSM. Your current method is way off.

Ah, the engineer's esthetic (no offense, I feel the same). Unfortunately for us, aftermarket parts are usually not as-designed. Just sayin', it's one of those realities. Anyway, to the PO, you might check under the rubber boot for fluid. It might be the cylinder itself that is leaking.

The fitting on the slave cylinder is a straight thread, not a taper, (I just looked at my spare cylinder) with no seat for a flared tube end either. Seems like it would benefit from a washer unless they did some precise machining on the flat seating surfaces. Maybe the factory parts are of higher quality than aftermarket. My car came with a copper crush washer, although I don't know if it's stock. And good old carpartsmanual.com shows a washer, but, oddly, it's on the end of the hose that does have the typical brake line flare fitting. Why the "please" on no washer? Datsun 240Z/260Z/280Z Clutch Control Hose and Nisan sells the hose washer GASKET-HOS :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com

Stupid cat...

Seems to me that if the heads flow well from the valve openings to the manifold surface, that constricting flow that soon will negate much of the work. On the other hand, if the "work" at the manifold surface is not matched in the bowl, and around the valves (unshrouding), then it may not matter anyway. I know that you shouldn't have flange at all projecting in to the flow path, not even a piece of gasket. It will create turbulence and ruin the flow. Who did the head work, it seems like they would have some recommendations? I looked at your Resto thread but don't see any mention of engine work. Don't forget to check the collector area of the header. If the flanges look like that it wouldn't be surprising to find a major clog at the collectors also. That header doesn't even look good for a stock head does it?

The idle speed screw actually controls air flow through a bypass channel. Turning the screw out (counterclockwise) increases idle speed. The AFM screw just controls the air/fuel ratio, at very low air flow (low RPM). It might affect idle speed but only indirectly and not much.

How does the ZX do with the use of a timer? Better than the thermal switch? Thanks for those links. I followed the second to Walmart - Find the Attwood Turbo 3000 Blower at Walmart.com. Save money. Live better. Fits my budget better. Looks like it might be okay mounted on the firewall. Summer project.

I wanted to get cooling of the fuel rail out of the picture. Isolating variables. There are only four air streams (four of the injectors are paired up) pointed directly at the injector bodies, underneath the rail. Plus the ZX mounting scheme, with the blower bolted to the side of the engine and the ductwork over the valve cover, is bulky and difficult to work around. In this setup the blower is off of the engine and the cooling tube can be slipped off and removed easily. It just lays on top of the engine under the fuel rail. The only attachment point is the slip fit on the blower nozzle. It's an experiment cobbled together from available parts.

After absorbing all of the ideas on where the heat soak problem originates, I decided to try the most direct solution I could fabricate and blow air directly on to the injector bodies. I have a ZX fuel system blower fan and ductwork from a ZX motor I had bought in the past but didn't want to use the bulky ductwork or the thermal switch (which doesn't seem to be effective on the ZX's anyway). So I bought a bathroom fan timer from Home Depot to control the fan (one hour range), and went to the wrecking yard and scavenged two 18" pieces of pre-heat tubing from a couple of 80s-90s Chevy S10 exhaust systems ($3). Taped the two pieces of tubing together, cut 6 holes in it over the injectors with an X-Acto knife, blocked one end and taped the other to the elbow from the ZX ducting which fits the blower nozzle, and mounted everything in the engine bay. The new ducting sits nicely under the fuel rail. It's made for the high heat environment of an exhaust system so should be fine. I zip-tied the blower to the condenser for my AC system, and the timer to my steering column. Considering its overall ugliness, it all fit in pretty well, even the timer on the steering column, and is mounted solidly. The pre-heat tubing will take a bend and hold it without collapsing. I used metal foil ductwork tape (Nashua 324A) on the tubing. There are probably better ways to do it, but I was in prototype mode. I've had it in for about two weeks and not had a single hot-start problem. But today I went in to Office Depot, after a fairly long drive down the freeway (hot engine and it's close to 60 degrees here today), and when I came out I realized that I was in the dreaded 10-30 minute zone and had forgotten to turn the blower on. I started the engine and had one of the worst heat soak problems I've had all winter. The engine chugged along on what felt like 2-3 cylinders for a good 1-3 minutes, which felt like 10-20. It finally settled down enough to leave. I went down the block to another store went in for about 15 minutes but remembered to turn the blower on, came out and it started right up like it was cold. Just passing this along for anyone that wants to try it. The air coming out of the holes shoots forward so mount them behind each injector to get good air flow on the injector body. I would take a picture but my engine bay is not meant for looking. I'll post a few links to parts instead. I'm trying to find a dependable automatic timer relay that will turn the blower on when the ignition is turn off but haven't found a good one yet. http://www.amazon.com/Standard-Motor-Products-Pre-Heater-Hose/dp/B000C7UPQU/ref=wl_it_dp_o_pC_S_nC?ie=UTF8&colid=30R38L6H5WA0Q&coliid=I2PEPLP3OQMVN8 GE In-Wall Spring Wound Countdown Timer-15304 at The Home Depot

The ring at the AFM is actually one end of a two-ringed wire. One ring on the AFM body, one on a mounting screw. The Engine Fuel chapter has a decent diagram of the grounds for the EFI harness, from the ECU. Doesn't show you where the connection is, but you can verify them all at the ECU connector..

Your local Nissan dealer might have or be able to get one. If not, Courtesyparts shows stock - Datsun 240Z/260Z/280Z Engine Electrical & Fitting Parts COIL-IGNIT :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com

Just happened to be browsing a book on turbos tonight and found a picture of a typical "floating-bush journal bearing" that looks just like those "brass" parts. Maybe someone blew up a turbo in the past. The book is "Turbocharging Performance Handbook" by Jeff Hartman, picture on page 113.

You're probably on a better track now anyway. By the time I got done with my charging system, I ended up at just the basics of finding a good voltage source for the S wire to monitor voltage, the L wire which comes through the Charge lamp, and the main charging wire for the battery after it runs through the fusible link. All of the original regulator wires are unused now, except the L wire. On the 76 system a problem I found that's not covered by the various internet schemes is that the brake check warning lamp relay power runs through the external regulator. It's yellow and runs back in to the harness. You can end up with it powered always or not powered at all, both wrong if you want it to work. You'll know that you might have this problem if you get a small spark at the negative terminal and hear a relay click when you reconnect the battery. That's another issue though, I don't know if 75 has it.

Do you have an ammeter or a voltmeter? I'm not sure when they switched over but the missing wire may be the charge lamp wire, which would be necessary for the alternator to energize and charge, but missing if you have an ammeter. Maybe you should be using the 240Z swap wiring scheme.

It was mild sarcasm. It sounded like you were going to buy a new PUC based on those numbers. You didn't give any pressure numbers either so who knows how you measured pressure. Some people just look for gas coming out of the hose. Have you checked spark strength, or sprayed some starter fluid in to the intake manifold? Pull a vacuum line, spray in to the hole, and try to start. If it fires up, runs, then dies, your ICM is probably good. If it doesn't, pull a plug and make sure it's not fouled.

Didn't realize that you had already solved the problem. I would call 354 ohms pretty close to approximately 400 ohms. Your money. At least you'll have a spare pickup coil.

The turbo engines use a totally different ignition system. The ECU controls timing and a simple transistor is used to fire the coil. They're not interchangeable with the NA engines. You should check fuel flow and pressure. Sounds like you're either out of gas or the filter is clogged again.

Yes, the resistor mod. It's easy, pretty quick and effective for richening the mixture across the whole air flow curve. I've read several accounts of people finding resistors in the EFI harness that looked like they were put there professionally. Installed and wrapped for a permanent fix. It seems like the system was designed on the lean side and people have been fixing it for many years by adding a resistor to the CTS circuit. I don't know if the ECU's are going lean, or the AFM's, or the ethanol in gasoline is putting things over the edge. If the ECU swap doesn't work, I would try the resistor next.

The intake backfiring is also a sign of a "bad" AFM. But I've "fixed" two AFMs that were lean by using the potentiometer in the coolant temperature circuit (just installed another spare AFM last week, and the potentiometer saved it. It was stumbling and on the edge of backfiring). You might try that. You could also measure resistance on the 6, 8, and 9 pins. If you don't get 180 and 100, the AFM might be going bad. It may be a higher ethanol content in gasoline making a slightly lean situation worse. Ethanol effectively dilutes the mixture, making it lean. For example, E85 engines use huge injectors and sometimes double up to get enough E85 in to the engine. Modern engines compensate through the O2 sensor, old systems are stuck with the factory algorithm. Pontificating... I've used a 78 ECU in my 76. The part number were the same. They performed identically. And 30 psi at idle is good. It should jump to ~36 if you remove the vacuum hose to the FPR.

I started at the end and stopped when you said you were going to sell the car. You should put an ad in the Classifieds section. If you're not selling the car, you should restate your problem for this forum. I did glance at the first post though, and it looks like you own either a stolen or illegally modified car, with the mis-matched VIN tags and body. If I were you I would report it to the police and get my money back from the guy that sold it to you. That might solve all of your problems and avoid future ones.

A super simple test that would at least tell you something would be to start the engine, turn it off without touching the brake pedal, then remove the vacuum line to the check valve on the booster side. If the booster has had engine vacuum properly applied you'll get a big hiss as the booster refills with outside air. This will tell you that the check valve is working correctly and that the booster chamber holds vacuum. If you don't get a hiss you might have the check valve in backward or the booster is leaking. It's a simpler way to do the tests described in the FSM, Brake chapter, without a vacuum gauge. Basically, instead of measuring vacuum with a gauge you measure it with your hear.

Why did you even ask?

There might be parts of the harness that are in good condition and easier to keep and use intact, than to try and rewire. If you don't live in a studio apartment you might as well keep it for reference, at least. Unless you're a wiring wizard who can figure out a wiring scheme from the FSM diagrams, assuming that they're complete and correct, and your own electrical knowledge.

It was worth a shot. Can't blame you. Thanks for the 1.25" number anyway.

I might have confused things by calling the shank of the bolt a "shoulder". A 10 mm shoulder bolt would have a distinct shoulder machined to 10 mm, I believe. The bolt in question is not a shoulder bolt.