Zed Head

Usually the exhaust system mounting plate is thin and doesn't seal when you use headers. The intake manifold should seal. You didn't really say if the intake was sealed with the new gasket or not. EuroDat mentioned the electronics and running lean. That problem is common. Might be worth trying the fuel tweak on the coolant temperature sensor circuit if there are no obvious intake system leaks. It's easy and it works. Make sure you fix that AFM though. http://www.atlanticz.ca/zclub/techtips/tempsensorpot/index.html

Looks more like you had a vacuum leak from the beginning. You should return the AFM wheel to its original position immediately. The only reason to move it is to move it back to where it started at the factory. It's not a tunable device. One thing that gets overlooked often is that a leak in the PCV system can let air in to the air intake system. Any air that does not flow through the AFM will lean out the mixture. The hose from the valve cover and the one under the intake manifold are both possible leak points. People sometimes use a smoke test to find vacuum leaks.

Not an expert. But, barely lower is what you'd get if the valve head was bent on the stem. Since everything is back together it might be worthwhile to pull the spark plugs and spin the engine by hand to see what the valve is doing. Does it get stuck or does it move freely. Then, if you're brave, spin it with the starter with the plugs out. Don't forget to disconnect the coil, or use a remote starter with the key off. You could also measure cylinder pressures if it spins freely. If the valve is not closing completely you'll get a zero on that one.

Sounds like it. Or somebody adjusted the lash too loose on that valve. You can compare the height of the valve when it should be closed (on the base circle) to other valves that are closed. It could be just stuck or it could be stuck because it's bent. Rocker arms jumping their lash pads is not uncommon when revving an engine that's been sitting. You can find stories. Many people just put it back together and carry on and never have it happen again.

People here call that the lash pad. That's not good, it would be holding the valve open. Any chance the locknut came loose on the adjustment side? Can you wiggle it by hand? Was it mine, I'd recheck lash from scratch.

If, by pulley, you mean that off-center cam-looking thing in the middle of the chain sprocket, that's the fuel pump eccentric. It is supposed to be off center, it pushes the fuel pump lever each time it passes by. Can't tell how many RPM "revving' is or what ping or knocking actually mean. But I can say that your valve lash seems tight. On a properly adjusted valve train the base circle (the part of the cam lobe with no hump) will not be worn since that is where the lash is, and the anti-rattle springs keep the wear pad off of the base of the lobe. The base circle is usually brown. Yours show wear all the way around. You might want to recheck valve lash. You might shine a light down toward the chain tensioner and see if you can tell how far out is extended. You can also set your damper pulley at zero and check your chain wear marks on the sprocket. The notch and groove. Make sure the tight side, driver's side, is tight.

Looks like overheating and/or lack of oil. Are they all like that? p.s. I wouldn't call that piston "slap". Slap is from loose pistons. That one got too tight.

Might find it in a bearing cross-reference somewhere. https://www.carpartsmanual.com/datsun/Z-1969-1978/electrical/alternator/12v-60a https://www.nissanpartsdeal.com/parts/nissan-bearing-ball~23120-65004.html This popped up on the Google. Read the description closely. 17 seems right. Has the Nissan number shown. https://smithcoelectric.com/products/5-4700-new-bearing-17mm-x-47mm-x-14mm-17x47x14

Looks like they sold out to the Holley conglomerate. It's the way the industry is going. Once the big guys own them the cost-cutting starts. Some of the smaller names seemed to benefit but I think that in the end everything averages out to mediocre. https://www.linkedin.com/company/aem-performance-electronics/ https://www.holley.com/logos/ https://en.wikipedia.org/wiki/Holley_Performance_Products in 2018, Lincolnshire Equity IV, L.P. sold Holley to Sentinel Capital Partners who merged the company with its Driven Performance Brands

Actually you have the simplest version of the ignition modules, with just one coil control circuit. You can try the swap in the engine bay, next to the coil, without doing anything to the factory module except unplugging it. Edit - actually disconnecting since you don't have a plug. EuroDat's mod is the slick, looks factory, swap method. But there are clues that you haven't mentioned. You've talked about RPM and the lazy tach needle the next day but haven't described what the needle is doing while it's running poorly. That's a good clue. If the needle is not steady and following engine speed correctly then that's a sign of spark problems. The other common electronics problem is the ECU solder joints. The test for that is to bang on the side of the ECU when things are acting up and see if there's a change.

I don't know how the relay associated with that retrofit works but, if it was set up likes today's EFI engines it would have a 5 second run timer as soon as you turn the key on, to refill the float bowls. Other carb guys know more. Nissans document describes what's happening pretty well. Percolation, they call it. They talk about being too rich but if the boiling continues for long eventually you end up at too lean. Anyway, their descriptions might offer clues. Good luck.

The bearing pressing has been discussed off and on around the internet. The procedure is counter to normal but it's what Nissan says to do. The question would be "how much force is necessary to get the bearing races seated?" The final torque value is only on the inner race and distance piece, not the balls and races. I haven't done one so don't know how hard it is to push the races in during installation.

I didn't really think that you would find anything but it was worth a look. It's not clear how the ignition modules fail, but they do at a pretty regular rate. If it was mine I would take it for a drive and see if the problem repeats. Take extra care to note what happens when it does. You only have this one incident to guess about. Stop immediately when it happens and let things cool down for a few seconds. Restart and see what happens. You need more data.

That would keep the fuel in the line at radiator temperature while the car sat. Probably around 150 F, guessing. Not good. Besides that, if the problem is after the car sits, it's most likely the float bowls boiling dry. Do you have an electric fuel pump or mechanical?

The key part of the "failing ignition module" statement is the "ing". It's not failed, it's failing. The heat generated from higher RPM must cause something to stop operating correctly, causing too many sparks. At least, that's how mine seemed to be failing. So, testing it cold won't show the problem. It would be an intermittent problem. Post a picture of the circuit board inside the module if you want to give it an ocular assessment. Maybe somebody will see a burnt trace or leaking capacitor. Any visible signs would be on the circuit board.

They can apparently get squashed from hard usage or accidents.

That's a lot of weld. Don't forget to measure your distance pieces.

The Parts Manual shows four variations. Might be a clue. https://www.carpartsmanual.com/datsun/Z-1969-1978/engine-280z/e-f-i/air-flow

Pretty good price for a 73. Minor modifications. $39,250. https://bringatrailer.com/listing/1973-datsun-240z-208/

Could you describe the MSD ignition system? Your 240Z came with points and a ballast resistor. Are you using the points to run an MSD ignition box?

Are you going to weld that yourself? Curious about the materials also, are they similar steels? That is a high stress area, and you'll have all of the force passing through the weld. You'll want a proper match of metals and welding wire and weld depth. It's on the inside so you'll only lose motive force if it breaks, at least no wheels will fall off. You're too deep in to it now but did you ever confirm that you need that extra distance? I spent a few hours building an adapter for the other ZX 3x2 CV axles so I get the urge to fabricate. I never used it but it was fun to build.

You work in Arizona where it never gets cold. Did you or your son ever break a windshield? You said you replaced dozens but didn't say that you never broke one. My first experience removing a windshield was in a wrecking yard. The owner was gone and his wife told me and my friend that we should wait but I told her that we could do it. It was about 35 F. A small tendril of adhesive was still attached (GM used a rope of sticky tar-like adhesive for windshield installs. Nasty stuff) as we tried to lift it out and it cracked. We left, I didn't pay for it (cause I was a punk kid), and the owner started calling me "Easy Money" after that. In the long run I paid him back by giving him a 66 GTO (the same one that I was getting the windshield for) after I wrecked it, and his son a 55 Chevy pickup truck after the axle bearing went bad. The statement was, basically, that old windshields, especially those with chips, are more prone to cracking than new ones. Just because you guys were careful enough to get it done doesn't mean the statement is not true. Anybody who's watched a chip grow in to a crack and spread across the windshield should know. Tell some stories about how to get it done. Heating the adhesive helps, a warm day helps, make sure that every scrap of adhesive is cut free (a PO might have tried to seal a windshield leak in the past). Stuff like that. Interesting though that by the statement it broke during installation. So the BS calling ia about the wrong part as are my suggestions above.

I don't know, that Amazon link looked new to me. Pretty interesting. Hope my memory is not fading...

The polymer adhesive layer probably loses flexibility over time. That could change the forces on the two glass layers. And besides the visible chips the whole surface of the glass is probably etched to a certain degree after years of road debris and acid rain and washings. A vast array of stress risers. As a whole, an old windshield would/should be more prone to cracking than a new one. One more opinion. Did @zKars ever get his windshield? He said he would post back in that other thread.

Interesting drama on BAT. Arizona retitling. https://bringatrailer.com/listing/1977-datsun-280z-98/#comments-anchor