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AK260

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About AK260

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  1. AK260

    AK260

  2. AK260

    Misfiring while cruising

    Great to hear, well done. [emoji106] Imho those plugs look on the hot side, look at this ... If those colours were on the same bank of 3 cyls I would have said carbs, but since they are not, I'm tending towards valve clearances. Now, two questions: 1. Have you adjusted your valve lash clearances? They determine how much / little or consistently across the cyls your valves open and shut and their timing relative to each other. I find my engine (a highly modified L28 but with a mild cam of 270 degrees and .46" lift) reacts very strongly to well adjusted valve clearances. It's more noticeable on a modified engine but the principle is the same for yours. 2. As for your idle, are you running a working vacuum advance? Have you checked it is actually working? Your mix at idle or part throttle will be lean and will require more timing for it to burn well. Mine has a base timing of 17 degrees (higher than stock due to cam) and vacuum advance adds 12 degrees at idle. But as soon as I go on the throttle and open the carb butterflies, the manifold vac drops and timing goes back to 17 + mechanical advance as the revs rise to a total of 34 degrees (without Vac! With vac connected, add 12 degrees to that). A lean mix without sufficient timing will burn hotter. With vac advance, you will find your idle will improve and engine temp at idle or cruise will drop noticeably. Also the cruising to on-power responsiveness improves (not to mention gas mileage). Think of it this way, imagine you have two plates full of gun powder on the floor, one packed with dense gun powder (rich) and one sparsely packed (lean). On the rich one, the gun powder particles are touching, on the lean one there is air between them. Then you light both from the centre - the plate with the denser gun powder burns faster towards the edge. Now imagine you had a fixed amount of time of say 1 second for them to burn before you dump the contents into the trash can. The fully burnt / rich plate dumps hot soot. The lean plate is still combusting and finishes it's burn in the trash can, burning the edges of the bin as it goes in (and that is the edges of your exhaust valves in an engine). Next time around, you light the lean plate half a second ahead of the rich plate. This time, both finish their burn before you dump them. The principle in your engine is exactly the same and your exhaust / header temps will drop with more vac timing at idle. Hope that helps, good luck! BTW, where are you able to do 100mph without getting a blue light escort!? Are you in Germany!? (Joke!) Or a test track?
  3. AK260

    Misfiring while cruising

    Agreed! Plug fouling at idle could be caused by other things like mix, lack of vac advance, etc. Get her firing well first and then sweat the other stuff later. ;) Is it safe to assume you've already changed your cap and rotor?
  4. AK260

    Misfiring while cruising

    Think of your gearing as a torque amplifier - it merely amplifies your engine's characteristics. So if you are bogging down @4K you have a power flat-spot that a long diff will make more prominent. L24s were renowned for having a flat spot at or just before 4K rpm - one way to "tune"' it out is to have a 6-3-2 exhaust header with long primaries and long collectors (the 2 bit) as per the Nismo or Janspeed design. The theoretical ideal (rule of thumb) is around 90cm primaries and 50cm collectors. See this fine bit of engineering ... http://www.datsun-zstory.com/echappements/headers/headers-race-sport/ Changing your diff will surely reduce the effect but the flat spot is still there. I just realised why you guys are getting such low revs, you are using an auto 'box, right? Apologies to the OP for taking the thread off track.
  5. AK260

    Misfiring while cruising

    I've used similar things before but the the cheapest way to see if you are getting spark is to get the engine running, set the fast idle to around 1.1krpm - take a plug lead off at a time and point it to something metal on the block - you will soon see/hear the spark. BTW did you get the new leads? Remember the old ones can have a break inside and give intermittent spark / intensity when vibrating under normal conditions. As a rule of thumb you should be sitting somewhere between 2.8-3.1k rpm at 70mph depending on which variation of diff ratios/gearbox / wheels you have. The typical range is somewhere between 21.5-22.5 mph per 1000rpm. Use a free app on your phone like track addict and you will have a better view of your speedo accuracy.
  6. AK260

    Misfiring while cruising

    I think your speedo may be a little optimistic - the longest R180 was a 3.364 which means you should get 22 (ish) mph per 1000rpm. Unless of course your gearbox has a super long top gear. [emoji14] Mine is pessimistic around 30mph (i.e. Shows 25mph) then gets accurate at 80 and optimistic above 90! Ahem - All tested on a track of course, officer! Don't always trust your old dials. Other possibility is that your rev counter is being pessimistic and you really are doing 100 in which case your real (not indicated) revs are around 4.5K RPM! And if you think that the max speed of your car is around 120mph and max torque at c.5.5krpm, then the 22mph / 1000 rpm works. Or are you running some super tall tyres!? :p
  7. AK260

    Misfiring while cruising

    100mph @3krpm!?!? That is a seriously long diff you have!!! So are these pics with new leads or your old ones?
  8. AK260

    Misfiring while cruising

    Of the list on rock auto I guess you can't go wrong with NGK. Glad your car isn't backfiring - mine took out the baffles in the silencer and deformed the whole thing - you can see where it started blowing through the joints!!!! [emoji14]
  9. AK260

    Misfiring while cruising

    Ps your number 6 looks like it's not firing at all when compared with the others - just get some new leads - they are dirt cheap! https://www.rockauto.com/en/catalog/nissan,1977,280z,2.8l+l6,1209248,ignition,spark+plug+wire+set,7224
  10. AK260

    Misfiring while cruising

    Spot on! [emoji106] Also try it on the coil to dizzy cap cable - which is where the majority of my issues lay. It looks like your engine earth strap is next to your oil dipstick. Thick black wire goes from block to body. Your coil has positive and negative low tension connectors. One is 12v from your ignition switch and the other is the 0v that the dizzy breaks / makes as it operates. Also you have low tension connectors at your distributor - look at those too. These connectors tend to corrode. Especially in the UK where we are constantly humid. IMHO plug fouling at idle is a red herring here and given your photos they look OK. I had an L series that drank a lot of oil and the plugs were not just sooty but also wet and black - it never backfired or missed when cruising or on power. So your plugs for the sake of trouble shooting this issue look fine.
  11. AK260

    Misfiring while cruising

    The way I looked at mine was v simple: eliminate every possible electric cause. I changed: the plugs in case one had a crack The dizzy cap and rotor The coil The wires to the coil by running direct from battery (fused of course) temporarily. Spark plug leads. Also Checked and cleaned up engine earth strap Replaced a couple of connectors - see this one that was holding by a single strand you can see coming out of the connector. Did each one at a time until I found the culprit - and I would say there were two issues in the HT leads and a potential other in the low tension connectors. Bear in mind I had rough running and backfire at revs and when on power and missing visible on timing light. So given my experience I would say your problem is electrical in nature not advance related. Good luck buddy.
  12. AK260

    Misfiring while cruising

    Not sure if you fixed this issue but I had exactly the same problem - turns out my magnecore kv85 leads were the culprit. I had assumed being advertised as high end items they wouldn't break down after just 9k miles but the coil end had disintegrated and 2 out of 6 leads would change impedance dramatically - from around 5k ohms to over 300kohms - when you waggle them. The guy on the phone at magnecore was condescending when I raised it with him and refused to believe their leads could possibly fail. It's all the customer's fault ! Changed them for 8mm leads costing 1/6 the price and the car runs sweet as a nut again. https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F181999641503 Check / change your leads too and see what happens.
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