WogsRus Posted December 16, 2014 Share Posted December 16, 2014 Ok so my new z has a weird miss, not always there. so back ground a bit. Apparently the engine is an ex targa prepped motor, looks like it runs a L28 block with an early E88 head and flat tops. So far i need to get on top of a weird miss that happens, like ignition but literally the whole ignition is new, all of it, new coil, leads, sparks, points, rotor, capacitor you name it, all new. One thing i found, it runs like 18 deg static timing by the timing light, i think it might be re curved dizzy when the engine use to run triples? The miss is like when whole car looses instant power cut, like ignition but could be fuel as the motor use to run triples not runs round tops. It seams not to rev all way out to 8K, seams flat from 6K onwards. What should i look at. I did check the plugs, clean but a bit lean i think, i have three bolt early carbs, how do i richen them up? I have tried to do search here but im usless. Quote Link to comment Share on other sites More sharing options...
oldmates260z Posted December 16, 2014 Share Posted December 16, 2014 What type of carbies is it running and with what air filters? I had this issue once with it sucking in the Ramflo filter element as the internal cage was missing. Quote Link to comment Share on other sites More sharing options...
WogsRus Posted December 16, 2014 Author Share Posted December 16, 2014 stock airbox with K & N air filter Quote Link to comment Share on other sites More sharing options...
WogsRus Posted December 16, 2014 Author Share Posted December 16, 2014 OK so worse this morning, thinking its timing, really is a miss, like nothing else, however, if you slam your foot down, it clears away, wander if its a lean miss? Ok need some help. I do notice it seams to drop of in performance after 5.5k, like it hits the wall and slows down, wander if tits the carbs. Quote Link to comment Share on other sites More sharing options...
luvemfast Posted December 16, 2014 Share Posted December 16, 2014 You mentioned earlier that you're running 18° timing. That might be a bit ambitious. Do you like your head gasket? Quote Link to comment Share on other sites More sharing options...
WogsRus Posted December 16, 2014 Author Share Posted December 16, 2014 If i run it at 7-9 deg, it pig roots and does not run at all, completely dead, missfire, pig root, not reving etc. Don't forget its a L28 block with aE88 head and cams of some sort. Seams 17 deg is sweet spot, clean revving and takes of like a bat out of hell Quote Link to comment Share on other sites More sharing options...
Administrators gav240z Posted December 16, 2014 Administrators Share Posted December 16, 2014 I do notice it seams to drop of in performance after 5.5k, like it hits the wall and slows down, wander if tits the carbs. My L28 with twin SU's, E88 head, cam, (10:1 compression or possibly higher!), exhaust etc.. feels the same. It doesn't miss, but it seems to feel a little flat after 5.5k rpm. The last owner of my car had a set of Triple Dellorto's on it, he had put the SUs back on when selling it. I remember when we drove it (test drive) he said it felt a little flat. It has always felt a bit that way, even after I rebuild and recurved the distributor, and tuned the SUs and put the correct oil in the dashpots etc.. I suspect when the previous owner of my car put the SUs on and they were jetted for the L24 displacement and not the bigger L28 - hence it gets lean and starts to run out of puff higher in the RPM range. Has plenty of low down torque and so forth. I would like to try richer needles in my car and might run a rebuild kit through them (the SUs), may also re-bush the throttle shafts if I detect any play in them which causes vacuum leaks and makes them impossible to tune up. How to rebush is demo'd here. What I would like to know however is what these roller bearings are? From here: http://www.ztherapy.com/products/SUReman.htm Throttle Shafts are sized to receive double sealed stainless steel roller bearings. Carb bodies are precision machined for shaft alignment and installation of both bearings. This alignment process in conjunction with the bearings virtually eliminates shaft binding, vacuum leaks and idle problems for years to come. I suspect your problem may be a flat spot and it would be worth going over your SUs to see what shape they're in. Quote Link to comment Share on other sites More sharing options...
WogsRus Posted December 17, 2014 Author Share Posted December 17, 2014 Heres a video, particularity bad today. PLEASE HELP ME Quote Link to comment Share on other sites More sharing options...
Administrators gav240z Posted December 17, 2014 Administrators Share Posted December 17, 2014 What distributor are you running? Still running points? If the distributor shaft is worn out, then you'll get excessive play and that can result in ignition issues like this. Quote Link to comment Share on other sites More sharing options...
WogsRus Posted December 17, 2014 Author Share Posted December 17, 2014 YEah points dizzy, swapping to a brand spanking new L24E dizzy from my brother wrecked skyline on the weekend. I am assuming L24E dizzy same as 280 ZX one? Not too sure about the shaft, will check tonight. SO thinking more ignition then fuel? Quote Link to comment Share on other sites More sharing options...
WogsRus Posted December 17, 2014 Author Share Posted December 17, 2014 Ok so, when cold no miss, when warm miss started again, fcuck it. Dream to drive with no miss. Also when warm engine backfires/burbles a lot more on decel then when cold. Quote Link to comment Share on other sites More sharing options...
Administrators gav240z Posted December 17, 2014 Administrators Share Posted December 17, 2014 Ok so, when cold no miss, when warm miss started again, fcuck it. Dream to drive with no miss. Also when warm engine backfires/burbles a lot more on decel then when cold. So maybe an electrical component that overheats when the car is warm? There is a capacitor on the side of the points distributor? Maybe heat it up with a heat gun when the car is cold and see if the miss-fire is there? Or alternatively it could be a dud coil? Again maybe a heat gun would help verify? Even if they're new it could be faulty. Quote Link to comment Share on other sites More sharing options...
WogsRus Posted December 17, 2014 Author Share Posted December 17, 2014 Bloody old school, LOL. Quote Link to comment Share on other sites More sharing options...
dazzed Posted December 17, 2014 Share Posted December 17, 2014 I also encountered that using a USB adaptor in the lighter socket effects early zeds ignition ( missfires) ?? Yes. Quote Link to comment Share on other sites More sharing options...
WogsRus Posted December 17, 2014 Author Share Posted December 17, 2014 so i went through the whole ignition, wd40 everything, re-gaped and checked wiring., I found that the ballast resistor wiring was cracked at the terminal wire thus when hot it could have broke down. The coil seams nice and cool now to touch which i don't recall being last time. Took car for a drive,seams ok bu down on torque so spark must be less. I am installing a brand new L24E dizzy from my brothers old car he has, its a genuine Nissan one so that might help. In regards to the carburetors, they say SU on them but who knows. Quote Link to comment Share on other sites More sharing options...
WogsRus Posted December 17, 2014 Author Share Posted December 17, 2014 Also, the timing marks are 20 deg at 1000 rpm it wont really idle lower steady, no idea why. if i set it to say 7, it simply does not pull and brakes down a lot, simply will not drive, ideas? Quote Link to comment Share on other sites More sharing options...
luvemfast Posted December 17, 2014 Share Posted December 17, 2014 Is the dizzy drive set correctly? Sounds like you may be a tooth out on the gear drive. I'm going from memory, but I think my hot L28 is set at 14-16°. You're going to have to do some research as to how to check. ie- set TDC, remove rotor cap, check rotor position blah blah blah Quote Link to comment Share on other sites More sharing options...
WogsRus Posted December 17, 2014 Author Share Posted December 17, 2014 Thanks mate, perhaps, i will be doing so over the weekend, Quote Link to comment Share on other sites More sharing options...
Linton Posted December 17, 2014 Share Posted December 17, 2014 Is the dizzy drive set correctly? Sounds like you may be a tooth out on the gear drive. it wont matter so long as you can turn the dizzy and get the correct timing set, the offset on the end of the shaft and the distributor base can only go together one way, my own is at least one maybe two teethe out in the oil pump and it purrs, but I have both the adjustment nuts at full rotation to compensate. my thoughts when its cold I assume you are on choke so more fuel less air no miss, probably fuel. but it does sound like ignition have you check ballast resister Ah you have 2 active posts well forget the resister then Quote Link to comment Share on other sites More sharing options...
WogsRus Posted December 17, 2014 Author Share Posted December 17, 2014 Yeah i went over wiring last night, so far, no miss, like i said the ballast resistor had dodgy wiring, which perhaps caused it, so far, drove into work all good. Quote Link to comment Share on other sites More sharing options...
WogsRus Posted December 17, 2014 Author Share Posted December 17, 2014 Ok so i did a bit of fiddling and so forth, did timing and fuel etc etc to get it to where i think its ok. Here is the two plugs i took out after a drive, taken from number 2 and 5 cylinder counting from front to back of motor. Cylinders does not seam to ping, but hard to hear over exhaust. I think black/brown dots is BAD no? Let me know your thoughts Quote Link to comment Share on other sites More sharing options...
dat2kman Posted December 17, 2014 Share Posted December 17, 2014 It's a points dizzy? Check static timing at whatever idle is, mark the base to the front cover, then remove dizzy. Pull the points plate off and check condition of the bob weights and the springs, under the dizzy points plate. It could be an issue in under there. When re-installing, put a new set of points in, f the contacts on the existing look a bit pitted. Sometimes the bob weights stick on their pivots, or a spring has fallen off. A dizzy is "re-curved" on a distributor graphing machine by simply bending the tangs holding the weight springs. The correct way is to fit a different tension rate spring, these were a Nissan Competition Part, but are NLA. Dont bend or alter anything, unless you know what you are doing. If this ends up not solving the higher rpm intermittent miss issue, next step, fit a new coil. Quote Link to comment Share on other sites More sharing options...
dat2kman Posted December 17, 2014 Share Posted December 17, 2014 The ballast resistor is used only on the "start engine" circuit, once engine is running it is not in use. A dry joint or a loose connection with a bit of gunk, that can cause higher resistance can also be a cause, but that would show up right through the range. Quote Link to comment Share on other sites More sharing options...
Enzo Posted December 17, 2014 Share Posted December 17, 2014 Hi, The bottom pictured plug is running leaner than the top plug. You should richen it up. A colour tune kit comes in handy for this. Also I noticed that you say you have trouble reving to 8000rpm. ( Bit of overkill for a street car). With a points distributor you may be experiencing point bounce as well with the higher revs. Combined with the leaner carb, it could be causing the miss. I would set the dissy to about 16 degrees BTDC with the vacuum disconnected and set all in timing no higher than 34 degrees. You will have to modify the dissy to limit mechanical advance for this. 16 degrees initial +18 degrees mechanical =34 degrees total. A reasonable starting point. David Quote Link to comment Share on other sites More sharing options...
WogsRus Posted December 17, 2014 Author Share Posted December 17, 2014 Thanks heaps will do, also some cooler plugs maybe? BP7ES ? Quote Link to comment Share on other sites More sharing options...
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