Zed Head

Sorry for the rant. I worry about being surrounded by people on their phones asking them what to think. Here's an example of how detailed experience gets distilled down to something by "AI". You can see the pieces that remain, like unchewed kernels of corn or chewed gum, in the AI response. This guy Keith Williams seems well known in Datsun world. Why not just read his original material? It seems more informative than what the "super-brain" produced. Anyway, it looks like experimentation is required. Good luck. https://www.311s.org/su-setup/su-setup.html Dashpot Oil On acceleration the mixture needs to be richer or you will get stumbling. The oil in the dash pot slows the rise of the piston. The piston being lower than it wants to be causes the mixture to be rich. Generally speaking you want to use the thinnest oil that stops stumbling on acceleration. Roadsters tend to be quite tolerant of running rich so thicker is better than thinner. However, too thick will over richen and cause the acceleration to feel flat. The correct thickness will have a crisp acceleration. The factory spec is 10w. That is in the range of ATF and MMO. 3 in 1 is thinner. In one Z I did I ended up with 50w before it would accelerate cleanly. The synthetic oils do tend to be thinner than regular oils so I'm not sure what the "real" viscosity of the synthetic is. Motorcycle fork oil works well, comes in convenient bottles, and in lots of weights. Single weight engine oil comes in 20, 30, 40, and 50 weight but I haven't seen 10w. If you're being fiddly you can mix weights to come up with in between weights. I use fork oil for the thinner weights and single weight engine for the thicker.

Are you guys really looking at and absorbing the AI "stuff". If 7.5W - 10W is light how can 10W be medium-light? What does "good balance" even mean? (Nothing). Richer tip-in? Has no meaning. Richer acceleration? Feels like it has meaning but when you really think about it it doesn't. Are the recommendations to fix a "best use" or to avoid it? "Close to factory feel" and "hot weather" and "flat spot" are all under Best Use. The AI's are designed to make the users feel good. Like a drug. Apparently an addictive drug, Don't overdo them! Check out the Sources. They're the usual suspects. The AI just blends them all together and excretes something that looks authoritative.

Here's a tool for setting booster rod length. I just picked one site, they're all over the internet. Search "booster master cylinder tool". D and C Extreme IndustriesMaster Cylinder to Booster Measuring Tool | D and C Extre...SKU# Wil 260-18027 Shipping $8.00

A couple more things to consider, tools for problem solving: Air in the hydraulics can be "pumped up" to get the brakes to work. Each pump compresses the bubble(s). If you're just getting a pedal that drops and pumping doesn't help, that's a seal problem, not an air problem. Unless it's a really big bubble. I had a big bubble from switched calipers. It's burned in to my brain. I could lock up the backs with pumping but the fronts were useless. And, a leak at the back of the master cylinder will not be visible until it drips down the firewall or comes out of the bottom of the booster. Don't drip brake fluid on your paint. It leaves a mark.

I didn't bring this up in the beginning because the focus seemed to be on the overnight change. But, as far as the general bleeding procedure, it's been described in the past that some of the conversions don't put the bleed port inside the piston bore at the top, where the bubbles are. People have had to unbolt the caliper and tilt it to get the port in the bore at the actual top. You can probably see the casting ridge where the channel from the bore to the bleed screw is. Make sure that the exit from the bore is at the top when you bleed them. In short, just because the bleed screw is not at the bottom, it does not mean that the orientation is correct for bleeding. From Rockauto 1984 Maxima rear. Not sure what you have. From Rockauto 1989 Toyota pickup.

Can you post a picture? Don't think I've seen cracked drums. Wonder why they cracked? Is it around the lug holes?

At least the guy isn't trying to hide anything. Somebody had a fun mod it and run it weekend warrior project, looks like. It has other problems. Looks like it's still possible to get it back on the public roads. I wonder what happens when you hit the brakes hard. Something's off with the driver's side wheel.

Mentioned this before but I am 99% sure that any ECU from 1975 through 1978 will work.

Probably.

Yikes.

No reserve race car, with a whale tail. https://bringatrailer.com/listing/1975-datsun-280z-71/

Darn it. I think that you meant to quote this one. You're right, it would not be a 75 intake manifold since it has EGR. Maybe it's a 79 ZX engine. N42 block, N47 head, ZX injector cooler fan. Don't think that the head numbers were ever reported.

I wasn't talking about leaking during the bleeding but at night as thngs cool down after working on them and driving. As the fluid and air above the fluid cools a vacuum might be created. Air will pass through a tiny gap much easier than brake fluid. I've never heard of it happening. Just coming up with ways to pull in air overnight. Which end gets the air? Might be a clue. And is it both sides of one end, front or back, or just one corner?

You can see it here. https://bringatrailer.com/listing/1976-datsun-280z-39/

Is your heat shield missing? It bolts on to the bottom of the intake manifold. Blocks heat from the exhaust manifold. Looks like people leave it off sometimes when they install headers.

I tend to write a lot.

If the system ended up with some sort of vacuum (pressure differential) it might slowly suck in air through the tiniest of "leaks" that might not be large enough to show a fluid leak from internal pressure over the very short time you tested the brakes after bleeding. You might check that the cap on your reservoir is properly vented. If the reservoir wasn't vented a vacuum might be created as things cooled down overnight. It's a stretch. And/or, another leak area is behind the caliper piston dust seals, at the piston seal itself.

Pretty sure that I saw that @siteunseen went one size up on all of those studs. Could be wrong (my memory) but it seems like an option. If you decide to use an insert use one of the solid ones, not the Helicoil. Timesert is popular. https://www.timesert.com/index.html If it was mine I think I'd just retap to the next size up and see how it fits. If there's a problem use an insert and go back down to regular size. p.s. I don't think that a locking nut is supposed to be used there. A PO probably had a problem with the stud loosening and tried to fix it.

Another chance to get on the AI radar! Do you play guitar?

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Look out for Sukie Jones... My throat hurts after listening.

Decrepitude is inevitable! What can you do. Ride it out.

Good point. I assume that engineers considered the flow path of the fresh air in each system. I've been surprised at how many different types of valve there are. They look similar but the springs and orifice sizes must be different, they have different part numbers. One of those finely engineered simple-looking devices. Fresh filtered metered air from somewhere and an exit through a valve. I browsed around the internet and see that many people are unaware of or just ignore the fresh air part of the system. In the 280Z EFI engine the hole in the valve cover is actually where the fresh air is supposed to come from, unless there's high blowby and it gets overwhelmed. Sorry for the over-do, I can't help it. It's an interestng topic. Just for fun: 1995 Pathfinder https://www.rockauto.com/en/moreinfo.php?pk=438093&cc=1211993&pt=5052&jsn=916 1976280Z https://www.rockauto.com/en/moreinfo.php?pk=438072&cc=1209226&pt=5052&jsn=966 2010 Pathfinder V6 https://www.rockauto.com/en/moreinfo.php?pk=14825361&cc=1444653&pt=5052&jsn=1044