NewZed

What kind of diff? The single bolt on the back mount looks unfamiliar. What's the front mount look like? The Arizona Z Car mount has brackets on the control arm pivots, yours doesn't seem to have those. Not really clear what you're working with. Looks interesting though. Did you build it or buy it? If you want to confirm that the bar is bending/flexing you could run a tight string across the top of the bar, from mount to mount, as a reference line. Distortion from the camera lens might be making the bar look like it's bending. If it's camera the string will look like it's bending also. All you can really say from the video is that the back of the diff moves away from the car body. But, if you look at how far the back of the diff moves and compare it to how far the bushing flexes, you can see that the back of the diff drops much farther than the bushing flexes. That's a long lever arm from the end where the mount is to the diff. Also, the hangers for the suspension brackets are tied directly to the body. So the "dogbone" is a reference point also. The back of the diff is definitely dropping and it can't do that unless the bar bends. Even if it twists on the bushings it still has to flex/bend also.

My mistake. Paint is plastic. Chemically and often physically. It's squishy.

I see flexing of the bar and the bushings. The back of the diff is pulling down. Usually the nose pulls up but the rotational force is pushing down on the back at the same time. So the front is very strong now and the back is the weak link. Stiffer bushings without a stiffer bar might transmit more twisting to the studs. Fatigue could be a new problem.

The system worked. Could be the seller got caught with poor heat treatment like a couple of the guys on this forum did when they had stub axles made. The concepts are simple but getting things executed correctly seems to be difficult. Are you going to share the seller's ebay name so others don't get trapped? CFJ im[plied that Silvermine sells them but they seem to have a decent reputation for quality. They've been besmirched, indirectly, Make sure you get the clips installed and seated.

Looked like the bar was bending then springing back, kind of like the original bar was designed to, although it may bend much more with more torque. The mounting area, the studs, didn't seem to move. You didn't give any details at all about how the mount is made or what material it's made from.

You implied that you had the wheel mounted on top of the paint on the brake drums. Generally, mounting surfaces should be clean flat metal. Burrs, dirt, grease, grime, paint should all be removed. I've been surprised that Nissan paints the flanges of the u-joint halfshafts. I scrape it all off if any is chipped. Tried to find a general internet reference and this popped up. Copied an excerpt. Lots of good stuff in the whole document, actually, even though it says it's for trucks and motorhomes. Load is load, a high performance Z probably hits motorhome loads.. https://www.alcoa.com/alcoawheels/catalog/pdf/ServiceManual-English.pdf

The 78 and on starters are gear driven, with an offset drive motor. They seem to be reduction starters, but I've never actually seen the gears or a description of their ratios so can't say for sure. They're not direct though, and it would be kind of pointless to offset them without taking advantage. It should lessen the voltage drop allowing more juice for spark and other electronics, as noted above. Never heard of the turbo car gear reduction starters, and the 78 + starters weigh less than the big motor direct drive pre-78 starters. So it looks like three different types are out there. At least one manufacturer describes them as gear reduction, for what it's worth. Picture from Rockauto site. Just a few more factoids.

The likes are that much more valuable. Who to bestow your like upon at the end of every day.

Soft plastic paint on a metal mating surface isn't really a good idea. It will creep and compress over time.

You don't seem to be measuring anything. There's no numbers. One thing that many people do when they swap parts is to compare the old to the new. You could have, and still could, compare(d) the old MC to the new one. Sometimes people have to swap the rods to get the new ones to work. Added a picture. With the pedal in the proper position, one way to get really close on the MC rod length is to adjust it until the clevis pin drops in to the hole easily. And a typical test for air in the system is to pump it up. If the system pumps up, in other words works better after pumping the pedal quickly, then there's air. The pumping compresses the bubble with new fluid. Anyway, good luck. Take some time and look at each piece and what it does. It really is a very simple system. A collection of simple concepts.

Those hose clamps look scary. You can get CV boot clamps, and a $10 tool to fit them. https://www.summitracing.com/parts/oes-25326?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-oem-specialty-tools&gclid=CMOxnZi35M0CFQeTfgodfqoH7g https://www.summitracing.com/parts/cwa-5013626aa?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-crown-automotive&gclid=CN7XiqS35M0CFZNhfgodlFQK3w

Spray some WD-40 or PB Blaster on first to help. They rust. Found a picture of the back on the inter-tubes - http://www.ebay.com/itm/Used-70-78-DATSUN-240Z-260Z-280Z-QUARTER-PANEL-EMBLEMS-PAIR-/262514806476?hash=item3d1f1a0ecc:g:G4kAAOSwmtJXVdBb&vxp=mtr

They're just a press fit, with spring clips. Pry up the edges and they'll pop out. Don't know how fragile they are so use a wide blade and work slow.

See if you can get a decent picture of the inside of the cylinder. That's where the corrosion/crud that damages the seal or gets stuck under its edges lives.

The seals are only good if they create pressure. Should have checked for pressure before removing. Sorry, but it's measuring you need to do, not more looking. The problem with just replacing is that you'll still need to make sure it's all assembled correctly. But, you're in the might-as-well zone now. Might as well replace since they go bad eventually and you have it apart. Odds are decent it will work right when you put it all back together. Ttake the new parts apart and make sure they're not contaminated with honing grit before installing.

You need to move on from the "maybes" and "seems" and take some measurements. I had a slave cylinder that leaked in the middle of its stroke when it got hot. It seemed right, and it held pressure. Just didn't move far enough. Took me a while to figure it out. And it was a new cylinder. But it was dirty inside.

The rocker panels are the stiff part of the metal box that is the chassis. They're like frame rails, tied directly to the fender wells. The floors, not so much.

It's just a few flakes. They might not even have left the top of the cylinder head.

You're not giving many details. Disassembled the clutch pedal, won't go in to gear, pedal doesn't feel right, adjust linkage every which way. It's not clear if the end of the clutch fork moves even a millimeter. See if the end of the clutch fork moves when you press the pedal. Or remove the line from the MC and see if you can generate pressure there. The cylinders are known to corrode at the ends over time. If the seal dragged over it it might be toast. The system is simple. The pedal and linkage move a piston, fluid moves through a tube, another piston moves, a rod moves, the end of the clutch fork moves. You need to determine which part isn't doing its job.

But does it go in to gear when the engine is running? That was the original problem. Now the pedal doesn't feel right.

I see it now. Worth more examination.

DEREK probably knows for sure but it looks like a core shifted during casting. The machining operation broke through and the QA department probably had to give it pass to let it through. Just a guess.

No pictures of rocker arm pads. Just cam lobes. They don't look terrible.

You might have ruined the seal in the MC when you let the piston come all the way back when you disconnected the pedal, or sucked some air. Or you put it back together incorrectly. If you're sure the mechanicals are right the best you can do is to bleed the system and hope. There's a chapter called Clutch (CL) in the FSM.