mckennar

Jim, I bet that's exactly what happened (someone cut it shorter and threaded it) because it does taper slightly at the very top of the rod for about 2 threads. I appreciate the offer re: the replacement rod - I think I'm just going to drill out the new knob and use a threaded insert.

No thread gauge but I do have one of those cheesy go/no go size chart things that you can pick up at a hardware store and it indicates M10. An M8 nut from my box o' bolts did not fit on the rod, too small. An M10 nut did fit. To ensure my old knob was in fact an M8, I took an M8 bolt from a kit and it threaded fine, no cross threading or fetching up. My RX8 shift knob is a known quantity, it is 10x1.25. It threads fine, tightens up nicely by hand with no cross threading or binding up. As far as a picture - The only one I have of the gearbox outside of the car is back when I bought it, and it only shows where it attaches to the ears. It is below.

I have a '72 240z into which I swapped a 5-spd from a 280ZX of indeterminate year. I took the stock shift knob from a '72 4 spd, went to screw it onto the 5 spd and it wouldn't fit. I kind of forced it while turning 10 or 15 times and it "felt" like it grabbed, but a quick 2-3 shift this morning popped the knob off and onto the passenger footwell. Frustrated, I took a spare shift knob from my former RX8 (M10x1.25) and it fit perfectly. What gives? I was under the impression that all of the non-T5 5 speed gearboxes had the same shift knob threading. This is most certainly not a T5 gearbox. Anyone else run into this before? Assuming this lever left the factory with this gearbox, does having an M10 threaded shift lever shed any light as to the year of the 'box?

@siteunseen & SheWantsTheZ, I wanted to update / close out this thread with the conclusion: Bit the bullet, drained & dropped the tank and while not quite as bad as yours, it was by far the absolute worst I've ever seen on a running car. Anyways, long story short, sent the tank out to be cleaned and re-sealed. Put it back in a few weeks ago, replaced both of the vent lines while I was at it and what a difference! I've driven over 200 miles so far and no stalling, no high idle, nothing. Runs like a top. So, bottom line, if repeated blow-outs of the fuel lines and in-line filter changes don't do it for you, bite the bullet, drop the tank and clean it out. Many thanks to everyone here for making that suggestion.

Update - blew out the lines w/compressed air, drained and filled the tank, replaced the brand new fuel filter with another brand new fuel filter... drove 3 miles, stalled again. Waited 10 minutes, drove 1.5 miles, stalled. Waited 10 minutes, drove 1.5 miles, baaaaarely got it into my driveway and it stalled again. I'm thinking I have about 20 different issues to tackle, not the least of which are vac leaks, exhaust leaks, etc. Realized these things have power brakes yet I have to apply about 80lbs of force on the pedal in order to initiate braking. Thought it was like my Demon and '66 Mustang w/o power assist brakes. Guess not. Applied shop vac to master vac, magically brakes became easier to press (engine off). Started engine and put my thumb in the line to the master vac, it barely had any suction at idle at all. All signs are pointing to a massive vac leak... which is weird because it idles rock solid at 500-600rpm when warm. I must have missed something when I pulled the air injection equipment. Also, carbs are original and have never been rebuilt. I looked through 32 years of receipts over the weekend and never saw anything about the carbs. I'll update this thread when I get this thing running properly.

Hey all just wanted to tag along with this thread instead of starting a new one - I recently purchased a 5 speed gearbox and here are the physical characteristics: "Medium" height shifter ears. Not the comically tall ones, but not entirely short either. One "ear" for the exhaust hanger on the driver's side. Speedo bolt at 6 o'clock. Reverse lockout/inspection (I've seen it called both) plate on driver's side. Definitely has a reverse lockout - can't dry-shift into reverse without centering the shifter then banging it to the right and back. Most recently came out of a '77 280z yet doesn't bear any resemblance to the imagery I've seen from early 5-speeds... yet at the same time doesn't have all of the indicators of a late gearbox either. Thinking perhaps that it's not original to the car from whence it most recently came. Either way I'm happy with the purchase, I'd just like to know what the heck this thing is so I can decide which rear end gears to go with. (excuse the presence/orientation/direction of the dowel - I just popped it in temporarily to test the shift pattern/lockout)

Yeah I mean I really don't know what to say here TheGrimOne... the car is a '72 with carburetors so no throttle body. No EGR but an air pump that is now in the "closet o' forgotten parts" along with the original exhaust manifold. Thanks for the effort, but it's decidedly misdirected. A small update - my landlord about had kittens when he caught me elbows deep in the engine bay this past weekend. He started blabbing about a part in my lease that says no working on cars blah blah blah fines blah blah blah eviction etc. Anyways, I haven't been able to drain the tank yet. I'm probably going to tow it to a shop unless I can drain and drop the tank and blow out the lines on a weekend where he's out of town. Will keep this thread updated as I get further into it.

Howdy all, Update: with ambient temps at 56f at 4:30 this morning, I drove it with a trail vehicle to the gym about 10 miles from my house. At mile 7 it started acting up. With the engine running (and idle slowly climbing towards the 1500rpm mark) I reached in and felt around for hot spots on the fuel lines, there were none. The fuel filter container was full to the top. The carbs, fuel lines, fuel pump (etc) were all cool to the touch. As I mentioned before, dumping cool water on the carbs / lines did nothing to resolve the issue and the idie continued to climb. I am now more than ever confident that there is some kind of fuel delivery restriction. I will report back as soon as I get a minute to work on it. I just wanted to say thank you for everyone's help... whatever the cause of this issue is, this outpouring of support, advice, tips and tricks has been the most comprehensive, least cynical first thread I've ever started on a website. I've been running around online automotive forums for 15 years now and this is one of the few where when a new person asks for help, everyone doesn't scream at them to use the search feature... which FWIW I have been doing since January trying to figure this issue out but thanks for not screaming at me to do so. So again, thank you all for your time, I will let you know what I find. Hope to see some of you at Z-Bash (Motorsport! Car Shows & Events - The Z Store, Nissan-Datsun 240Z-260Z-280Z-280ZX-300ZX(Z31/Z32)-350Z-370Z Parts) this upcoming weekend. I'll be the only guy wearing a Volvo Motorsport shirt. Cheers, Ryan

One more thing to add... when its doing its stalling-under-load thing, if I put it in neutral and pull to the side of the road, the revs will typically be at 1100-1300 (typically the car idles at 600-800). If I let it sit in neutral on the side of the road and do nothing, the revs will slowly climb to at least 1500, perhaps more. I don't wait around for the revs to go higher, so I usually shut it off and let it cool down a bit. Of note, the higher the revs are in neutral, the more susceptible the car is to stalling under load.

Each time it has stalled it has been on the side of a busy thoroughfare. By the time it limps its way back to the garage, I'm usually so frustrated with it that I just leave it. Plugs are brand new as of about 30 miles ago, old plugs were black but not overly sooty. I'll pull the plugs, buy the linked in-line spark tester and report back. Thanks. EDIT: looks like that tool just shows if there is vs if there isn't. There's no way of telling the quality of the spark. I know there's spark because I can fire it right back up when it stalls, or if I catch it in time I can let off the throttle until the engine catches itself, then put it in neutral and it will idle all day, but the second I try to give it any throttle under load, it'll stall.

Also to answer another question, when it starts to stall, the tach needle slowly makes its transit from wherever it was at speed, down to zero. It isn't an instant drop. Jam it back into gear and it pops right back to whichever RPM you're at based upon gear / speed.

Hi all, thanks for the replies. Crane XR700 w/Crane PS20 coil. Both warm to the touch when the stalling happens, but no warmer than the surrounding metal in the engine compartment. I can "make" this car behave in this manner pretty easily... start it in the morning, drive for 15 minutes, happens every time without fail. Start it again 20-30 minutes later, drive it for 5 minutes, it stalls again. It comes on slowly during the first time of the day that it happens. So you're driving, and 10 minutes into the drive WOT makes it bog so you back off, thinking maybe you're giving it too much fuel. 2 minutes later, 1/2 throttle makes it bog so you back off more. Now you're going 45mph on the freeway. 2 minutes later, any throttle makes it bog and you're praying you make it up the off-ramp and into the 7-eleven. 1 minute later, it won't even idle. Wait 10 minutes, rinse, repeat until you get frustrated and call Hagerty roadside assistance for a tow. Re: spark quality, besides pulling a plug and eyeballing it, is there a more exact way of testing this? Also, I've been assuming (perhaps incorrectly) that when there's a weak spark condition, the amount of unburned fuel exiting the exhaust would produce a smoke and a raw fuel smell both in the front and in the back. There is no such smoke or smell at idle or under load. Its these contraindicating symptoms that brought me here. I'm going to keep searching, worst case I'll drop the tank and start digging around in there but not looking forward to that mess! It's over 3/4 full. haha. I'll have another crack at it this coming weekend and report back. Ryan

Howdy all, First off wanted to say I've been researching vapor lock and I'm not 100% that's my issue. 1. Car starts fine, idles fine if not a bit lumpy. 2. After the car warms to operating temp, head on out for a drive. Idle: 600-800rpm when warm after first start of the day. 3. After 5 - 10 minutes of driving, the car will start to become unresponsive to throttle to the point at which if I give it any throttle at all and take it out of gear, it'll stall out completely, and I have to either jam it back down into gear if I'm going fast enough or just coast over to the side of the road. 4. Once on the side of the road, however, it fires right back up. Oddly, once it starts back up, the idle is around 1300-1500, as though there's a vacuum leak that isn't present when the engine first hits operating temp, and it has zero power and will stall almost immediately if you try to put it in gear and give it throttle. 5. If I wait 10 minutes, the idle is around 1100rpm. 20 1000 RPM. 30. 900 RPM. 40. 600-800rpm. Drive for 5 minutes, it stalls, idle is back up to 1300 - 1500 and no power. 6. These stalls happen regardless of direction being turned, accel, deceleration, etc. 7. While this is occurring, manipulating the choke doesn't have any impact. 8. With my wife following, she does not note any black or brown smoke during these episodes. Ambient temp: 61f. Not hammering on the car at all, just going 60-65 on the freeway, but happens in town too. New fuel pump, filter, lines, spark plugs, air cleaner, damper oil, a few vac lines, etc. When this happens, there's plenty of fuel in the fuel filter housing and there is a good bit of fuel in the tank. Stock SU carbs, round top. Electronic ignition (new-ish). None of the insulation wrap remains on the fuel lines, HOWEVER immediately after this happening, when I pop the hood all of the fuel lines are cool to the touch. Even the carbs are pretty cool. I tried dumping some cool water on the lines and carbs and that got me a bunch of strange looks in the 7-eleven parking lot, but the stalling issue persisted. The car is new to me, and the previous owner (who has owned it for 30+ years) says it never happened to him before. I'm a fuel injection guy, to me carburetors are basically voodoo. I know what they do, but how they do it? Beats me. Suppose it's time to learn... Things I'm going to do/check next weekend (after Z-Bash, naturally): 1. Timing 2. "Quick & Dirty SU Tuning" checklist 3. Vacuum 4. Fuel pressure Any ideas beyond that would certainly be appreciated. Thanks again.