jvandyke Posted July 23, 2018 Share Posted July 23, 2018 (edited) my kid (17) either inherited or absorbed his old man's car infatuation, a couple weeks ago, while he was trolling craigslist for his usual favorites, he comes across an X-drag car (streetable), '72 with a zz4. Was made in Carson City back in '96/97, somehow found its way to Michigan and into our greasy little mitts. It's pretty far from it's former glory, a little (VERY little by Michigan standards) rust but ratty interior and tons of flaws, but she runs and goes like stink....most of the time, anyway First question and most pressing: It's got a zz4 with a Holley 670, stumbles very badly on tip in, drops to idle, usually recovers, you can tease it along. Gets better when warm. So far research shows many jet up a bit but not sure what's in there now, going to pull it apart and see. (a few minutes later: 65 primary, 68 secondary, not that I would know but that seems kinda small found this thread that suggests 68 primary, 76 secondary) running an automatic, TH700r4 I think. B&M Hammer shifter that is very FUBAR'd, hard to find a gear, once in she shifts fine. I plan on running through the set up procedures and adjustment may solve it. Anyway, happy to find this resource and hope to glean pearls of wisdom from y'all. We have a fascinating collection of old receipts (including a stack of drag times) so have an idea what's in there but who knows this far down the road, ya know? Edited July 23, 2018 by jvandyke add to gearbox info Quote Link to comment Share on other sites More sharing options...
jvandyke Posted July 31, 2018 Author Share Posted July 31, 2018 moved to 68 primary, 76 secondary, also found the fast idle adjustment screw had been bottoming out on the intake (seemingly stopping the primary butterfly from ever achieving full throttle position, hard to believe). Re-worked that. Goes like stink. Electric choke now releases the butterfly from high idle like it's supposed to. I think we're making progress. Quote Link to comment Share on other sites More sharing options...
jvandyke Posted September 4, 2018 Author Share Posted September 4, 2018 It's been running pretty good until a couple days ago, suddenly any attempt to apply throttle and it dies. We pulled the primary bowl, cleaned, did a little ignition maintenance, new plugs, cap, rotor, just because we should have anyway. No impact. Something went south suddenly. Thoughts? Quote Link to comment Share on other sites More sharing options...
jhm Posted September 4, 2018 Share Posted September 4, 2018 Sounds like accelerator pump? The diaphragm can become damaged or otherwise non-functional, but it's an easy fix. Quote Link to comment Share on other sites More sharing options...
jvandyke Posted September 4, 2018 Author Share Posted September 4, 2018 It's pumping gas into the carb though. I'm thinking of just getting a full rebuild kit anyway, of course, you know what they say, 90% of all carb problems are ignition problems! This was true on the '62 Galaxie I've been working on, Rebuilt the carb to end up with a new distributor! Tonight we swapped out cap and rotor. I've read vac, adv. going bad can do weird things. It would barely idle and was rough, it started suddenly, seems like it's missing to me. It was running quite well for weeks then would barely idle and die on touching the gas, limped home and here we are trying to figure it out. 1 Quote Link to comment Share on other sites More sharing options...
jhm Posted September 4, 2018 Share Posted September 4, 2018 Yeah, carb rebuild never a bad idea...might go a long way to resolving many of the issues you've been experiencing. Good luck with it. Holley produces a ton of parts and upgrade kits for their products. Quote Link to comment Share on other sites More sharing options...
jvandyke Posted September 4, 2018 Author Share Posted September 4, 2018 Yep, except that we had it dialed in for the last month. All systems go. Weird. I'm going to proceed under the assumption that it's a carb issue, and tear into it.....again. Something maybe just slipped out of adjustment, vacuum leak, or some dirt in a passage............maybe. Quote Link to comment Share on other sites More sharing options...
jvandyke Posted September 9, 2018 Author Share Posted September 9, 2018 carb rebuilt, must be ignition?, starts and idles, rough like it's missing, (exactly like before) so thoughts?, rebuilt carb, checked filters, checked fuel supply (pump works fine) new distributer cap/rotor/plugs, tickled the timing a little we also tried to snug up the valve clearances a tad, FWIW Is it possible the cam jumped a notch? Quote Link to comment Share on other sites More sharing options...
Miles Posted September 9, 2018 Share Posted September 9, 2018 You mentioned rebuilding the Holley carb. Did you check the float level? Easy to do on a Holley. See the Holley manual. Quote Link to comment Share on other sites More sharing options...
jvandyke Posted September 9, 2018 Author Share Posted September 9, 2018 I did not yet. I know I have to but since the car ran the same after I was done it "shouldn't" be the issue. Quote Link to comment Share on other sites More sharing options...
Miles Posted September 9, 2018 Share Posted September 9, 2018 24 minutes ago, jvandyke said: I did not yet. I know I have to but since the car ran the same after I was done it "shouldn't" be the issue. Could be an issue. Also, fuel pressure. I assume that you have a fuel pressure gauge installed in-line near the carb? The Holley manual will specify optimum fuel pressure. Quote Link to comment Share on other sites More sharing options...
jvandyke Posted September 9, 2018 Author Share Posted September 9, 2018 yes, pressure gauge present at carb and was okay, headed out to check level and pressure, the pump (some old Holley type) is loud but seems to put out sufficiently, gunna turn towards ignition again soon, I do have to recheck valve clearance, i haven't done a hydraulic lifter like these before. I think I'm doing it wrong. Problem predates my messing with clearances though. Quote Link to comment Share on other sites More sharing options...
Miles Posted September 10, 2018 Share Posted September 10, 2018 At idle what is the PSI? At around 2000 rpm what is the psi? Quote Link to comment Share on other sites More sharing options...
jvandyke Posted September 10, 2018 Author Share Posted September 10, 2018 had 7psi on crank and crappy idle but then I noticed it dropped to nothing....??? so you maybe onto something, if fuel pressure is all over the map.....voltage test at pump we had only 4v intermittently during crank, then I rigged up a different source, pump worked well, back to 7psi but no love running, could have flooded it by then. I don't know if this pump is hooked to oil pressure or what even.... Quote Link to comment Share on other sites More sharing options...
Miles Posted September 10, 2018 Share Posted September 10, 2018 (edited) Sounds like you need to make a detailed checklist for each system (ign and fuel) and then rule out each component. For example: Fuel System: Fuel pump has 12 volts Fuel pump grounded Fuel pump works Fuel lines clear Fuel filter clean / unobstructed Holley recommended fuel pressure Floats set per Holley manual Carb CFM correct for your engine Carb mechanical linkages set correctly Correct carb vacuum port connections for your engine Is there an oil pressure safety switch installed that turns off power to the fuel pump if the engine quits? etc etc etc Pencil and paper are tools too! Edited September 10, 2018 by Miles Quote Link to comment Share on other sites More sharing options...
jvandyke Posted September 10, 2018 Author Share Posted September 10, 2018 (edited) agreed, we need to dig deep to figure out how this beast was built, I suspect electrical issues at either the pump and/or the ignition system, if we're not getting a consistent 12v to critical systems all carb work is wasted (well, good to do in any event). Maybe the ignition switch is flaky and circuits on "run" or "start" aren't seeing what they're supposed to see. thanks for bouncing ideas off me. We know it was all good so it can be again, the street avenger 670 with our recent re-jet and choke linkage work was good so back to trouble shooting electrics. It is a cobbled up mess of wiring. How would an electric pump "normally" be wired in? I suspect off the oil pressure sensor circuit but who knows. Edited September 10, 2018 by jvandyke Quote Link to comment Share on other sites More sharing options...
Miles Posted September 10, 2018 Share Posted September 10, 2018 Could you post some clear sharp pictures of: Carb fuel and vacuum connections Ignition wiring Wiring at fuel pump. Also, how is the fuel pump wired? Off ignition? After market relay? Was the stock green fuel pump wire used (green wire is above the passenger kick panel and terminates in a taped bundle next to the fuel tank)? Recommend using the green wire with a Painless fuel pump relay for simplicity and maximizing voltage at the fuel pump. Quote Link to comment Share on other sites More sharing options...
jvandyke Posted September 10, 2018 Author Share Posted September 10, 2018 I'll try to grab some pictures of ignition and carb fuel/vacuum later tonight. Fuel pump is some orange wire to + and the - runs to chassis mount. Not the stock green. I need to trace it back to it's source and see where they wired it in. I'm pretty sold on the idea we have electrical issues at this point. It was not wired very well. Fuse block is hacked up and broken, we've already had to clean up the mandatory melted connection (I cleaned it and it stopped blowing fuses and getting hot). I'm thinking a good winter project would be to rewire everything, or at least investigate every circuit and clean connections, grounds and rework as needed. Of course, with a month of driving left here in Michigan we want it on the street for a bit yet, if possible. A 355hp 240z, really? Who wouldn't want it roll'n!! Quote Link to comment Share on other sites More sharing options...
Miles Posted September 10, 2018 Share Posted September 10, 2018 (edited) I had the same experience with my first 72 240Z (father and son project). The PO basically hot wired everything to get the car to run and drive. Spent weeks rewiring his mistakes. MSA has new fuse blocks. http://www.thezstore.com/page/TZS/CTGY/classic10a03 Useful information Download a Factory Service Manual (FSM). http://forums.hybridz.org/topic/48825-factory-manuals-some/?page=2&tab=comments#comment-1208329 Download electrical schematics for your car. PDFs are easier to read than those found in books. Some are in color. Buy the book How to Restore Your Datsun Z Car by Wick Humble. It will save you hours of searching for "how to" info. Focus on searching Hybridz as 99% of questions have already been addressed. Start bookmarking Z car parts suppliers - there are many! Remember these are 40 year old cars and will need restoration to be safe and drivable. Join ClassicZCars.com website and search there as well. Become well informed about modifications before asking questions. People will be more inclined to answer informed questions. Search the forums. Useful Links: https://www.datsun-240z-upgrades.net/ Recommend the headlight relay harness http://zhome.com/ https://www.zcar.com/ http://www.classiczc...com/index.html/ http://www.zcarparts.com/ http://www.arizonazcar.com/ http://www.jagsthatrun.com/index.html Edited November 25, 2018 by Miles Quote Link to comment Share on other sites More sharing options...
jvandyke Posted September 10, 2018 Author Share Posted September 10, 2018 great stuff, much appreciated Quote Link to comment Share on other sites More sharing options...
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