daughter.and.datsun

@NewZed Ah! Forgot to mention new plugs (which are all receiving spark) and a cleaned and inspected/measured distributor cap. The engine seems to be functioning well. I'll post a video next time I give it a go. It seems to move through gears smoothly (I last took it up to about 3rd trying to get above 30mph on a flat road), and the tach moves smoothly through RPM, but it's just as if the output power curve has been adjusted down to near nothing. Things sound smoothish too (aside from a singular rev-matching clicking sound coming from around the engine). All good suggestions, I'll try them out. Re: transmission, I used to be able to get up to above 30mph in first gear, but now I can rev up pretty high keeping it in second and only make it to 20mph. I have to take it to third to gut up that 30mph mark. I'm ready for the races, for sure 😊 Re: timing, I suspect that the owner before me swapped in a whitehead performance sprocket gear or something similar, as well as the chain, because I can't find any bright link on the chain. So I don't know what's going on there, but I also haven't touched it between the working time and the not working time. This is something I've wondered about - if my timing light measures 10degrees, does that mean that whatever's going on with the dampener or chain tension, it's firing at 10degrees? Or does it simply mean that spark is firing when the mark is at 10degrees, but who knows what's actually happening with the pistons? No need to respond to any of that - I truly appreciate the pointers you all have given so far! Thanks!

@NewZed Is there any good way to check if water is in the tank? My sender float is likely bad, so I was going to drop the tank sometime soon to investigate that. Any notoriously bad gaskets or anything I should look out for? Again, thanks to you both. This is an interesting line of investigation!

Thanks for the suggestions! @NewZed, automatic, 4 speed. The water idea is very interesting. I was driving it daily at the beginning of this year, but I stopped doing that around February (working from home). It's also right around then that it stopped delivering power... The rubber on this car is real bad, and it wouldn't surprise me at all if the gas tank was leaking. What would be included in a "tuneup"? Within the past 6 months I've done everything mentioned in the original post, plus replaced engine+trans oil, oil filter, fuel filter, thermostat, flushed engine coolant + peak cleaner + new coolant, new trans auxiliary cylinder, new trans fluid, new brake fluid, bleed all those lines. I've kinda been just fixing and replacing stuff as I'm able in a attempt to get it running close to "smooth". @rossman, I was curious about this as well. What's the best way to check? At 0 on the timing mark, the camshaft lobes in cylinder 1 are in "rabbit" ears configuration, both pointing up, symmetrically. But I guess that would mean that just the valves are in sync, not necessarily the pistons?

I'm trying to diagnose a few things on my 75 280z 2+2, and I'm wondering if they might be related. Any help would be appreciated. Also, does anyone know why the section of my camshaft above cylinder #2 is red? Video. In summary, I can't seem to get power out of my engine. It used to run "great", but now I can barely get the car over 30mph. I ran a compression test, fearing a blown head gasket, but though the readings aren't great, I would have expected to get over 30mph with them (1: 170, 2: 156, 3: 167, 4: 169, 5: 160, 6: 165). That #2 cylinder seemed especially low, so I ran it with a tsp of oil in the cylinder, and no change - still 156. My vacuum is measuring low at about 13 in of Hg. I replaced all the old vacuum tubing, but it's still running low, even with most subsystems' vacuum lines blocked off. Fuel is spraying well out of all injectors. Fuel pressure is at 38 psi with the fuel pump on, but engine off, then drops down to ~30 psi when idling. Using a timing light, I adjusted the distributor til the engine was at exactly 10 degrees by the timing mark. I lashed the valves back in the day at cold, but I definitely hear a clicking from the engine that I don't love. Based on that and everything above, I imagined that I must have just screwed up the lash, so I opened the valve cover and checked, but no, the lash was exactly where I left it. So I don't know. Any pointers, ideas, or other debug steps would be appreciated. And yeah, if anyone knows why that section is red on the camshaft, I'd love to know! Thanks everyone. Valves in action