Zed Head

Thanks, that's the picture I wanted to see. And there's not a lot of info there really. I wonder if other things helped also like the thickness of the washer under the nut. Maybe even the shape of the nut's clamping surface. I think the breakage is more a flexing/fatigue break, than an actual yield break. Could be all of the people switching to 280Z axles really just need to switch to 280ZX nuts and washers. grannyknot was in the process of installing ZX CV's. Not sure where he ended up.

Here's a nut source - http://www.thezstore.com/page/TZS/PROD/23-4573

I was thinking about the 240Z axle weak point. Borrowed a 280ZX axle picture from here - https://www.fototime.com/ftweb/bin/ft.dll/detailfs?userid=7DC317B08EDB4B2EA837F708D07C9769&ndx=19&albumid=180EC34916C34BD7850ED1A4EBA6F840&pictureid=0F5C07D338644ADBAE151D14EE4BFDF1 and the 240Z from here - http://forums.hybridz.org/topic/49194-differential-cv-lsd-hp-torque-r160-r180-r200-r230-diff-mount/ and here - http://www.thezstore.com/page/TZS/PROD/23-5020R Notice that the same tiny nut is used, leaving a big stress riser at the base. The breaks occur on the same diameter. The larger splined section doesn't seem to be any advantage in strength. Maybe why they went back to 25 spline. It does allow a bigger bearing though. Even the big 300ZX 39 spline axles use a small nut diameter. http://www.modern-motorsports.com/stub-axles.html

Nissan used a self-locking nut on the ZX's, so no need to stake anymore. You should too, they're available. As for damage, don't overlook that the damaged portion doesn't do any work once the nut is past it. If the threads won't damage the nut, then you might as well leave them that way. The smaller axle question has been raised before. Could be that they redesigned it and removed the stress risers that existed in the 240Z design. It would be interesting to see the two side-by-side. Or that the ZX suspension isn't as hard on the axles as the Z's.

Makes sense. I've seen the problem described before but can't remember the solution. The early 240Z's have booster and MC complications often. Matching the right parts. Year of car in the title will draw some eyes.

That's a picture of your brake booster. The tip of the rod sits in a cup at the base of the master cylinder piston. Not really clear what you did or are doing. That looks like an old dirty booster, what's new or restored? What is not working? What document has the measurements you're checking?

A follow-up thought - #6 is typically the detonation cylinder. Where head gaskets blow and rings break. Mis-set timing, low octane fuel, overheating; could be the cause of the problem. Doesn't help fix it but might help focus. Unless oil splashed up on to the valve seats, which seems unlikely at low cranking RPM, the oil in the cylinder raising pressure still points to rings. If it were my problem, I'd use a borescope to check for cylinder damage first. If there is none, and it runs well, and you get lash set right, take it out for an "Italian tune-up". Nothing to lose. Sometimes people baby their new motors when they should be using them to break them in right.

I tried it and namerow too. Nothing significant happened. It takes heat and lots of time. Worth a shot but be careful. Most of the videos are about small watch parts. These parts are huge n comparison. The chemical reaction generates gases that might be flammable. Don't expect magic. It's been around for many years, and considering how many broken studs in aluminum have happened over those years, you'd think something so easy would be more popular.

You have current following a wrong path. The charge lamp shouldn't get power with the key off. Check the circuit before the lamp and meter. Sounds like your problem doesn't have anything to do with the alternator.

You should always give a number where measurements are involved. "Out" isn't enough. The locknut can be very difficult to loosen and you can break other things,including your knuckles when it does come loose. I use a small sledge hammer to tap on a wrench to break them loose. The mass does the job without much overshoot. The cam lobe does look like it has wear on the base circle which would imply the lash is too tight, or non-existent. That can burn a valve. If you're set on doing it yourself we can come up with a bunch of tricks. But if you have a friend with experience, you'll probably learn more and be ahead in the end if you let him do it. You might just get the valves adjusted then go drive it hard to reset things and break any stuck rings loose. Inertia, heat and high energy fuel burns at 5500 RPM should loosen anything stuck, on a running engine. I think those magic oils might have an effect on an old rusty engine that hasn't run for a while but you're way past that. Could be the engine's hard to turn because it's not fully broken in yet.

Actually that part is shown in the link I gave. I missed it. Part #19, coincidentally. Seems like a lot of work. It's at about the very highest driest point in the transmission. But, while it's open... 32858-U6700 http://www.nissanpartsdeal.com/parts/nissan-seal-lip~32858-u6700.html

This link should help you visualize a little bit better. I think that o-ring is the only seal and it's basically a dust seal combo oil seal. Oil can only get up there by splashing and capillary, no real driving force for it to leak. Doesn't look there is an internal seal, so your "just leave it" idea may be the way to go. http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/transmission-control/5-speed That chipped gear is your reverse gear. You'll probably only notice it as a grindy growly noise when in reverse, I think, but it might be difficult to engage since there is no synchro, just two straight cut gears meshing. You'll be mashing those damaged teeth against another set of damaged teeth. Pretty common I think, although yours is pretty bad. Comes from angry people with bad clutch control cylinders. I found a chunk of reverse on my 4 speed's drain plug magnet. Not from me, from a PO. You want to look at the points of the dog teeth on the gears, and the internal teeth on the couplers, and the points on the synchros. They should be symmetrical and sharp. Eurodat has rebuilt a 5 speed, he'd have some good ideas.

Is the hole centered and perpendicular? What didn't work with the extractor? On your way to "bigger" for an M10, the remains might come out. You can't get to M10 without doing that anyway, so really all you can do is keep drilling, and/or get better extractors. You want the stock size or bigger, so M6 isn't going to work.

But if the hole has already been drilled and tapped for the heli-coil/insert, he's kind of limited. He might just have to do what the last guy did. Could be an SAE thread. Doesn't look he did the right work for the stock bolt, that's why it pulled out.

Examine your old bolts and see if one has a different thread pitch or size. It does like an insert but no telling if it's correct for the stock bolts. It looks oversize, and like there was enough extra room to pull it out of the thread. You'll need to know size and pitch to insert a new one. Take it off the bolt and see what the locking portion looks like, at the top under the bolt head. Just for fun.

A PO might have got them mixed up, who knows. If you did strip the top threads, or they were already stripped and you stripped the bottoms, you might just run a long bolt in there to the bottom and see how much thread you have left. Measure travel from when it grabs to when it stops. Then find an appropriate bolt, or cut a long one to fit.

If you have access to a bore scope that would be the thing to do. A broken ring would probably leave signs as MM says. Very light signs, hopefully. I've read of people disassembling old turbo engines that didn't have any visible bore damage and having the rings fall out in pieces. Probably depends on the ring, and the lubrication, and how it breaks.

I think that every water pump bolt is a different length. Make sure you didn't get one in the wrong hole. The threads should grab with at least 1/4" of bolt to go before the head, maybe about 1/2". Pretty sure also, that under no pressure, you can have a bad bolt and still have no leaks. I've seen a few broken bolt heads on systems that looked like they were leak-free, even in use. Not recommended but a sign of something off in your case. You might have some other issue going on.

Here's a picture of the plate from 1981 ZX engine. Had it off recently. 5 speed manual transmission, all stock junk yard car.

Wouldn't be surprised if Datsun Spirit would fix it for you. Only 5,000 miles, kind of looks like a broken ring. Put all of your paper work in order, it probably shows due diligence during break-in and maintenance. Not a huge job, he could probably do it in-car if he wanted to, although, based on reputation, he might want to give it a good look-over out of the car. Forgot that you're on the opposite coast. Still, he might assist financially, at least with parts, if you can find the right shop to work on it.

Trust but verify. Eiji could tell you something, I'd guess. Chrome rings can take a while to seat. As Mark M. suggested, a cylinder pressure measurement might be telling also . Leaky compression rings should show there. Bad valve seals and guides can allow blowby on the exhaust side. The head was done by Z Car Performance. Not sure who that is. You're still in that short-term vs. long-term dilemma. Vent the fumes and drive short-term, fix the issue long-term. Interesting problem.

Could be he got a rebuilt head from Datsun Spirit and a short block from California Datsun. I'd go through the papers and try to suss out what's what. Why does Datsun come up redlined for spelling?

Aren't the two piece units for automatic transmissions? You did an auto to manual swap, right? I wonder if the later auto units have a smaller hole, still two pieces.

By the way, older floats are basically just tin bubbles. High pressure can bend/crush them, I think. Carb people went to plastic in later years. Hope you're not at the start of a trail of fixes.

Just went over this pump with jxq. That pump uses a bypass port to regulate pressure. I'll bet there's something blocking it. Not sure exactly where the passages are but the instructions describe screwing a bolt in or out to get some variation of pressure, probably by shrinking or enlarging the port. I'd remove that bolt and see what's in there. Here's the instruction sheet - http://www.jegs.com/InstallationInstructions/600/650/650-4070LP.pdf