Captain Obvious

Here's a pic of one of the cylinders. Not as much material added as the one in your pic, but definitely a bunch added. Does this look reasonable? My days of building up a 300 bhp motor are behind me.

That's awesome!! So just how big was the smile??

Some notes about the temperature sensor and the thermotime switch. There are two trouble spots with the connectors. First trouble spot that the electrical connectors up at the thermostat housing are the same style and it is possible to get them mixed up. Other than the color, I'm not sure if there's a quick visual way to tell if they're correct. (If original stock) One of them is brown, and the other is gray. You can see the colors in the pic you posted, but I don't remember which is which. The second trouble spot is caused by the fact that they used two short pigtail harnesses to those two devices that end in bullet connections right near the #1 fuel injector. So since they're bullet connections, they could be swapped there too. One of those is supposed to be wrapped by a piece of tape (red I think) as an identifier, but many times, that has fallen off over the years. So I'm not saying yours are swapped, but the point is, that even if you have the connector on the right sensor, they could still be swapped elsewhere. You'll know for sure if you check the resistance tests in the FI bible. Last note is about the thermotime... The only time it should do anything at all is while the engine is cranking trying to start. It should be completely non-existent at all other times. So it should have no effect while you're driving around. If you want to, you can completely unplug it to see what happens. Might take a little longer to start your car when the engine is cold, but other than that, you should notice absolutely no effect.

Jon, What's something like that worth? I've got a P90 here collecting dust that someone has done that kind of work to. Not quite as extensive, but similar.

Have you done any of the testing from the EFI handbook (commonly called the EFI bible)? https://atlanticz.ca/zclub/techtips/efisystem/280zfuelinjectionbook.pdf Most of the testing there is done at the big ECU connector. I would be interested in hearing what your coolant temp sensor resistances are both cold and hot. And about pulling off a plug wire to check for a misfire... Not good for the ignition system. A better way is to pull off the injector connectors one at a time and see if the idle changes. Lastly, your compression numbers are definitely low. Did you block the throttle wide open while you cranked the engine for the compression test?

Pooky, I'm not sure I understand the problem(s) you're having... How bad is the problem? Is the car drivable? What's the worst of the problems? Maybe we can start there and knock them out one at a time? Also, @mgood is and active member and he's in the Pittsburgh area. Maybe he has some input for local help?

Well regardless if they flow the same, that's pretty annoying. The color may not matter, but on my engine, I would want everything to at least match. So I have no idea if the size of the opening on the bottom is the only thing that would affect the flow rate. I kinda doubt it. I suspect there are other internal geometry areas which could affect the flow rate too. In other words... Just because the hole in the bottom is the same, I wouldn't assume they flow the same. You could test them to compare the rates:

Sorry. One more thought about the timing chain and the tensioner sticking out... So the 240 slack side guide (the curved side) has a slotted hole at the top and two holes at the bottom. You have your guide with the bottom bolt going through the inboard of the two holes. I know this because I can see part of the outboard hole poking out from under the bolt head. But a pic here from @siteunseen, he has his lower bolt through the outboard hole. This effectively pushes the guide further in and tightens the chain: While putting in a whole new timing set is rarely a bad idea... What are the chances that the majority of the slack in your chain is due to an improperly installed slack side guide? I'm more of a 280 guy and the 280 guide is a little different. Just one hole that the bottom so no decision making on which hole to use.

Well color of the plastic doesn't necessarily indicate the flow rate of the injector, but to answer the intent of the question... Yes, if the new injectors flow more than the old ones, then you'll likely have to retune the system. But hopefully now that you have the other bugs and issues worked out, it should be a much easier process.

Good. I was thinking that some of the timing kits do not come with the guides, and I would certainly take the opportunity to replace the guides if you're doing everything else. Man that tensioner is really hanging out there. Looks like you were on the hairy edge of that thing popping out of there completely while the engine was running. Hope the new timing set takes care of all that.

Yeah, that definitely doesn't look right. Something wrong with the chain and tensioner, etc. Chain stretch, guide wear, gear wear... All together is allowing the tensioner to be waaaaay too far out. I think you need to pull the valve cover off and probably do a whole timing set. Easy at this point since you're in so far already.

Well lets see... If adjusted properly and working as designed, absolutely none of those items should have any effect at all at idle. Charcoal can - Disabled at idle EGR - Disabled at idle BCDD - Disabled at idle Cold star valve - Only active while cranking the engine, so disabled at idle

About the spring compression tool... You won't be able to use the "hooks on the cam" version if the cam is removed. (Duh.) Here's some pics of my latest valve spring took contraption. A little faster to use than my previous contraption since there's less wrench turning:

I spy something... Old Honda maybe?

LOL. I think he woke up not just thinking about one, but in fact, he work up WITH a Disney princess. I think you get significant bonus points for that!

Unrelated to the harmonic balancer key, but I got a question. Your timing chain tensioner is really sticking out pretty far... Is the head off, or is everything up top still in place? Timing chain wrapped around the cam gear and everything? if the answer is "yes, everything is installed and engaged", then I think it's time for a new timing chain and guides.

Well you've got two obviously bent valves, and marks on other pistons as well. That makes the whole top end suspect to me. The point is, the compression numbers may be more related to issues in the top end than the rings. However... You're this far in and it would suck to do a bunch of work on the top end and put it back together with a tired lower end. Who would ever do such a thing.

I take it back. Other than the valve dents and occasional other minor blemishes, those pistons don't look bad at all. If you don't have a really good condition other option, I'd run those. Must have been a trick of the camera. I was really expecting serious destruction. And you can see the sizing numbers now. Not cylinder number. It was just luck that the only one you could see before was #3.

I think someone did something like that... @zKars maybe?

Oh, and about the number stamped on the top of the pistons... The stock pistons should have a number on them, and there should be faint stampings on the block deck surface for each cylinder and the numbers should match. At least the first number. The stock stamping numbers represent "size", not "location". That "3" stamped in your piston does not look like a stock stamping to me though. Here's a couple pics from my engine:

Well there's your problem!! Nice to find the smoking gun. Good luck with the project. So you were talking about the condition of the rest of the pistons... Maybe it's just the camera or deposits on top of them, but I don't like the looks of them at all. Other than the dent, number 1 looks OK, but the rest of them worry me. Pitting on top? Detonation maybe? Is it a trick of the camera? Are all the rest of them smooth metal underneath the crud?

Happy anniversary!!!

Yes, read through the EFI bible. And then read through it again. Compression test. Intake manifold vacuum test. Fuel pressure test. Ohmmeter tests. Ignition timing test. And if you have a few extra minutes, clean some connectors. If you're looking for a place to start, start in the passenger footwell where the heater core leaked and corroded the connectors on the passenger side of the trans tunnel. Also do the temp sensor, the AFM, the fusible links and the fuse block. There are other people who can add much more value about the transmission and driveshaft stuff than I can. I could survive in the wild there if I had to, but there are other people who are experts in that area that will cover you there.

LOL. Glad to help my friend!! I'm just a guy with a Z who types a lot, but I try to add value where I think I can.

LOL. I like it!