Zed Head

The voltmeter should always work even with the key off. Sounds like you've lost connection through your main fusible link. there's a fuse also but I can't tell which one it is. There's better diagram below this one.

Some people swap in the 3.9 just for better pickup in 1st gear. 4th gear is 1:1 in both transmissions. If the engine is running well you probably won't mind the high revs. I've had my ZX 5 speed with 3.9 on the local freeways at ~60 mph in 4th and it's not bad. Probably won't bother you. You might find yourself starting out in 2nd gear though, with the 3.321 1st gear in the 4 speed. It will be like having a 3 speed.

A hot spot, boiling, creates a vapor pocket. Just like air in the system. Pumping compresses the vapor pocket, just like it compresses an air bubble. Seems plausible.

@Mark Maras it's just a regular distributor with timing control inside. It does all six at once, like moving the breaker plate on a regular distributor. Here's a pretty good review of detonation. Timing, heat, lean mixture...all can lead to detonation. https://www.enginelabs.com/news/detonation-what-causes-it-and-how-to-control-it-using-efi/

I think that lower vacuum when revving is a sign of a leak. At higher air flow the leak gets overpowered. Don't forget the EGR system. It's a known problem.

It's sounding like it might be a detonation problem, from too much advance. Still haven't seen the initial timing, just the instructions for installing the distributor. Seems like a 50:50 fault. 123's instructions aren't clear, but, on the other hand. verifying timing is a basic automotive skill. And the L series engines are known to be detonation prone, so knowing your timing is even more important. One of those live and learn things.

I was thinking the same thing but got distracted when he said it wasn't like brake fade. Boiling and brake fade are different things. Boiling would kill the pressure immediately. I was going to suggest that a brake line might be close to an exhaust pipe or engine part, which might explain why it comes on so soon. Check all of the lines, shield the MC from heat, make sure that the brake fluid is pure and fresh.

Maybe your CSV and/or thermotime switch is drawing too much current. It's on a parallel circuit with Pin 4. Instead of covering Pin 4, maybe disconnect the CSV and thermotime switch. It might delay starting but it should start if that's the problem. I don't have a CSV anymore and my car starts. I usally give it about 5 crank/spins, wait about 30 seconds for fuel to vaporize then start it up. You might also try starting fluid just to see if you have a no-spark or a weak spark or an injection problem. Finally, I just remembered that I had a starting problem once, but it was when things were hot. My EFI relay was fried and opened up when it got hot. So, the EFI and fuel pump relay's are a possibility too.

Pretty sure he describes it in the what will it make video. Tried to find where he talked about timing but my computer sucks for videos. https://www.classiczcars.com/forums/topic/58542-home-built-z-full-video-build/?&page=27#comments

The timing light tells you what your timing is. It is what the light says it is. Not sure that fiddling with the distributor will help things unless you want to run with 20 degrees initial timing. That's pretty high. You could easily end up at 40 degrees at 2500 RPM which your engine might not like. Some of the 280Z distributors even have 11 degree weights, for a total of 22 degrees on top of initial. I don't really know what's happening with your problem. I'm still leaning toward vacuum leak. The Aussie Home Built Z guy just posted a video about having to run very high advance numbers for timing then finding out that his intake manifold wasn't bolted down. Big leakage. I think it's in his "Dyno day" video. Once he fixed the vacuum leak he got back to normal.

This isn't enough. The initial timing advance number needs to be verified with a light, at least. Ideally, the person doing the install would then verify both MAP and centrifugal advance by revving the engine with and without the vacuum hose attached. If you just go through their procedure and end up at 15 degrees initial you'll be over advanced when the engine is running. Actually, I'm pretty sure that there is a post out there somewhere about the install procedure not working right and having to go back to basics. Trust but verify. Without the numbers there's not much to go on.

That's what is on top of initial. If initial was set to 10 then it's 39 at 8000 RPM. Plus there's the MAP curve underneath. Ideally the timing would have been verified by a timing light.

Could be from detonation. Detonation breaks rings and ring lands. Any chance you could describe or show the advance curve that you were using? And the details of the engine? Is it stock compression ratio? Could be the problem wasn't losing advance but having too much.

You said that you made your own "booster lines". When you say booster do you really mean master cylinder? The booster just has a vacuum hose. Pedal going to 1" from the floor would not be a booster problem. The booster just adds assistance to the mechanical parts. But there is a solid metal path (with one chunk of rubber in the middle) from the pedal to the MC. Sounds more like an MC seal problem.

Numbers are always good. Report the numbers, then do the standard practice of adding oil to the cylinders to see if they help seal the rings. If the oil helps you have a ring problem, if it doesn't you might have a valve problem. And don't forget to open the throttle before cranking. And remove all of the plugs so that you get some good engine speed.

You're welcome, as is 123. They make a good product, and, obliviously, by your firsthand account, stand behind it no matter how much abuse they take from customers. That's a pretty good recommendation. They should thank you.

How do we tell who wins this conversation? I win if you find a problem that is not timing related. You win if nobody ever buys a 123 distributor again. I'm rooting for me.

The AAR does the same thing as the idle adjustment screw. You could just open up the idle adjustment screw to see if it starts and holds idle. If it works then the idle speed will slowly increase the engine warms up. It will be a good clue about the problem though.

Fighting the world's irrationality, one simple internet post at a time...

It's called a coincidence. Two unrelated things that happened at the same time. Your engine was about to die anyway, it just happened to happen right after you installed the 123.

You're "bad-mouthing" a good company, based on a lack of knowledge. I do know how engines work, and I know how to determine the cause of a failure. You have jumped to a poor conclusion and are sticking to it, no matter how much rational advice you're given. You're spending more time defending a bad position than actually trying to find the truth. That's why I'm here, to find out what really happened. I did not read your email exchange with 123. But if you communicated with them like you're doing here I can see why they gave you problems, and why they refunded your money. You just wore them out.

You haven't clarified anything for people that understand how engines work. No offense intended, that's just how it is. Loss of timing advance as indicated by the "app", smoke smell, poor running, low compression on one cylinder. Just a list of things that happened that might or might not be connected. Sorry. Your frustrated, but you're not making things more clear with your posts. Go get some real information. Confirm valve lash, check spark plugs for signs of detonation, add oil to the cylinders for the compression check to see if it's rings, do a leak down test. Do more.

If you find something like a bent valve or loose rocker arm that is causing the low compression, it's going to be awkward...

Your case would be helped immensely if you could rationally explain how timing problems cause damage that would cause low compression. That lack of reason is why the 123 guys weren't helpful. There's no cause-effect. It might be coincidence.

I'm just showing how rants almost never turn out well. Losing advance would cause the engine to run hotter and probably smell gassy. Did you smell fuel and did the engine get hot? You didn't provide any proof that the lack of timing advance caused the problem, whatever the problem actually is. You didn't actually tell us what the problem was, just made indirect inferences about a damaged piston. That's the problem with rants. So many words in the head that the important ones get left out. If you start over with just the details of the engine problems we might have a solution out here. Your issues with 123 aren't going to stop anyone from buying a 123 ignition system though. Seriously, they have too many success stories.