Captain Obvious

Haha!!!

I bought this car used a couple years ago, and I don't know the history of the engine. I did get some pics from the PO including some shots with the head off the engine, so I know it's been apart at least that far. I don't know if he ever pulled the cam off the head or took the towers off the head. It's stock parts (cam is Nissan "A" grind stock), but I don't know if it's original to this car. I suspect that it is, however. I've been driving this car on that engine since I bought it, and have never had a hint that I had trouble like that brewing. No idea what happened. I was not at high RPM's when it let go, and I don't think I've ever hit redline with that engine. I take it to maybe 5K often, but that's about it. Anyway, no idea why it finally let go, but it's gone now! So I haven't dug into it at all and don't know if that rear cam section is seized in the journals. I kinda doubt it. I suspect it spins just fine. I'll find out when I start taking stuff apart. And about a path forward... I could either put a new cam in that engine, or... Exactly what I was thinking as well. I kept telling you I was going to do it this summer, right? The only problem is that it's Z driving season right now and it would be faster to toss another cam into my existing engine. Yeah, me either. That's the "whatever remains, however improbable, must be the truth." part!

Sorry guys. I was trying to be cute and I guess the issue doesn't come across so obviously in the video. That's what I get for holding my antique crappy camera in one hand and reaching in with my other hand to crank the engine. If you look at the camshaft while I'm cranking the engine, you'll notice that only the front half turns. The back half doesn't move at all. My crankshaft completely cracked into two pieces. This is just behind the center support bearing:

Uhhhhh.... Did you watch the video?

So I'm out driving around today, just minding my own business... All of a sudden, out of the blue, it starts running exceptionally poorly. Somehow (still not sure how), I managed to limp it about five miles home. Get home and start the troubleshooting. It's completely missing on the rear three cylinders and front firing out the intake like the timing is way off. So, what can cause a complete miss on the rear three cylinders and run like turds on the others? ECU? Nope. That's not it. Dropping resistor? Nope, not it either. Bunch of lash pads fly out? Nope. "When you have eliminated the impossible, whatever remains, however improbable, must be the truth." https://youtu.be/4nE4QhK4LMY Woof.

Everything on the engine works better when warm. They really don't like running when cold, especially at cold idle. In fact, that's why there is usually some sort of idle speed boost method employed that can be engaged at cold idle. For the 240 and 260 Z's, that idle boost is built into the choke mechanism. And for the 280's that function is performed by the AAR. The point is... If you are not employing the use of some sort of cold idle boosting method, or if your boosting method is not artificially raising the idle enough, then it would be perfectly normal for the idle to go up as the engine warms up. Other thoughts? If you are having some issues when you first hit the throttle you may be running a little lean. A lean cold idle is an unhappy idle. If you're running a little lean, the idle would get better when the engine warms up. That all seems to dovetail together. Sounds like you feel reluctant to come to the forum for help? Don't worry about that. Bring it.

Yup. That one with the bruised nose is my local buddy's. He was going to fix it, but he got lucky and turned up a replacement instead that was in really great shape. The luxury he had was that he was not in a hurry at the time and wasn't under the pressure from a painter to get parts yesterday. No prob. Glad to (try to) help.

For the collective, here's a pic of the dent on the nose of the hood I mentioned above. For those of you with body experience... How hard of a repair is this? I know everything is repairable with enough time and effort, but where on the scale does this fall?

Sending you PM...

I believe my buddy @GGRIII (you met him at my place at the wheel bearing party) has the original hood from his 260. It has the traditional parking lot dent on the front point, but other than that, I believe it's straight. He was going to fix it but found a near perfect replacement instead that saved him some time when he did his car. Would you like me to find out if it's for sale or if he had plans for it?

I sure do and I bet I'm not the only one!

LOL! Whew!! Close call!

I've got a tiny (tiny) bit of molding experience, and in my miniscule experience, it can be really really hard to fill a cavity and have all the air be properly displaced by the filling liquid. Since the block and head (not to mention the heater system) are rough and complex internal shapes, I would be very very surprised if you can just pour water into the radiator cap hole and have 100% of the air in the system be exchanged with water on the first try. I bet there would be significant pockets of air remaining after the fill. And that's where the overflow system comes into play. Putting some rough numbers on it... The volume of air in the system will expand closely related to the ideal gas law, while the volume of water in the system will expand at a much smaller rate. Quick search on the web says the volumetric coefficient of expansion for water is .00021 while air is .0036 . In other words, for the same temperature change, air expands about seventeen times more in volume than water does. That can certainly cause a vurp. It is my belief that the air will eventually be trapped in the filler neck as bubbles circulate in the system. The filler neck acting as a vertical trap as the bubbles flow by and getting pushed out the overflow when the system pressure increases. Then (assuming an overflow bottle is connected and has liquid in it) when the system cools down and contracts, it will pull liquid back in where the air used to be. I also do not believe this happens all at once, but can happen over a number of warm-up / cool-down cycles after filling. So... The bottom line? I think you should connect up the overflow tank, put some coolant in it, top off the radiator, and then heat cycle the system a couple times. If you are watching the tank, you might even see some bubbles burp out. If that's the case, the level in the overflow tank will end up a little lower than when you started because some of that liquid will be pulled into the system. And after a couple cycles, hopefully you would have all the air worked out.

My point about the gas being compressible means that it might not be fine. Just because it doesn't overpower the spring in the cap and push anything out, doesn't mean it's OK. In fact... When the system is working properly, there is SUPPOSED to be some liquid pushed out of the cap and into the tank. Then when it cools, that liquid is supposed to be pulled back in. With the cap on, if you aren't getting anything at all pushed out, that is another indication that you might have air in the system.

About the burping... I suspect it could just be an air pocket somewhere that hadn't worked it's way out. If you've got a gas bubble anywhere in the system, it will expand a huge amount compared to an equal volume of liquid and can push vurps of liquid out like that. The recovery tank and two way valve built into the radiator cap is intended to eventually work that gas out of the system and replace it with liquid. The gas is also compressible though, and it will compress first, before the system reaches the cracking pressure of the cap. If you have too much gas in the system, you may never even reach that cracking pressure because the gas will just compress. So with that in mind... Do you have a recovery tank installed or are have you been running open system?

Why yes... Yes, it does. Enjoy.

Welcome to the club! You are reading the manual correctly. There should be nothing connected to the anti-stall dashpot. Even though it looks like a vacuum nipple, there shouldn't be any hoes on it. The dashpot should just be left open. And a couple of the other vacuum lines are mixed up accordingly. The non-California 76 cars (which it appears yours is) used a system to disable the distributor vacuum advance until the car is in top gear. Not sure why they thought this was necessary, but in 77, they decided this was not necessary and eliminated that feature. So if I'm reading the manual correctly (pages EC-9 and ET-1), it appears the three-way line from the throttle chamber should go to: Throttle chamber connection Carbon canister control Timing control solenoid valve And then the other side of the timing control solenoid valve should go to the distributor advance connection. So where in PA are you?

I'm glad the story was that boring! Although a harrowing hair raising saga would have been much more entertaining! And I'm also glad that you've got a set of hubs put together now that are issue-free. And if you've got a gap between the flange and the outboard bearing, that's definitely a raging clue as to the previous issue. 1.6 thousandths can be a LOT when talking about bearings. Just for forensic analysis... See if you can determine if that gap is the same all the way around the bearing. If it's the same all the way around, in theory it shouldn't cause what you saw. But if it's .0016 on one side and zero on the other (which is what I suspect), then it's indicative that something is bent or you got some piece of grit or metal shaving trapped under the bearing race. In any event, it's almost definitely related to the problem.

I don't think the contact cleaner drying out is what is causing the change. I think there's something else going on. Are you sure something is really changing, or is possibly a placebo effect?

Clearly (and not surprisingly), there are people viewing both this ClassicZ thread and that BAT sale. Right after I brought it up here, they started talking about the dash cap on BAT and they're all over it now. It's an easy issue to fix. Expensive, but simple. "there has been some discussion of this car on a prominent Z car website, Classiczcars.com" Woot. We're prominent!! So just to be clear... I don't see anywhere where the seller ever portrayed this car to be a "completely correct" example. So all the chatter from people (like me) about the things that are "wrong" is info for the next owner who wants to make it better. That car isn't done, but it's a beautiful starting point!

Beautiful car. I took a quick look through the comments and I think there is more of an issue with the tone of voice being used to point out some of the incorrectness, rather than the incorrectness itself. The insinuation of questionable intent: "i just find it to be very strange how you own over 15 Z cars and you dont know ...... Just like you didnt know .... lol. or maybe for some reason you are pretended not to know but indeed you do.. what ever it may be." Uhhh.... OK. Something I see that I'm surprised that hasn't been mentioned... That's a dash cap screwed into place, right? That bugs me. Also, the shift knob... It's the "right" Nissan knob, but it's still wrong. And there was some discussion about the carb correctness... The car is said to currently sport three screw SU's and the seller says they are the correct carbs for the year. I though three screws were used in 72 only? I'm no expert, but I thought a 70 car should carry four screw SU's.

Oh wow! That's cool. And brave!! Those sort of journeys are often good stories. Was it an entertaining eventful journey, or was it a smooth sailing boring story?

I like the shot next to the original wood knob. That's a great contrast between old and new!

Haha!! Good luck! So out of curiosity, what year are you working on anyway?

I was taught that if one foot on the floor didn't stop it, you should put two feet on the floor and get up. You aren't going to fall asleep anyway.