RedNeckZ Posted May 12, 2002 Share Posted May 12, 2002 I need some help for my car. Just moved from Colorado to North Carolina. I have a 71 240Z with a L-28 block with a E-31 head/Cam/Header/three 45mm DCOE Weber carbs with 37mm chokes in it. I am running a 50F jet as the idle jet. It seems to be to lean. Does anyone from this area know what I should be running in it? I have tried changing the time and such. But it still runs rough and back fires at times. Any help would be great. I am staying in the Raeford area if that helps. Thanks, Rich. Quote Link to comment Share on other sites More sharing options...
Guest LAYTON Posted May 14, 2002 Share Posted May 14, 2002 i dont know but i have some 45's im cleaning up and have them totaly tore down while it apart i wanted to make sure i dont have your problem either cuz my motor hasnt even been fired yet Quote Link to comment Share on other sites More sharing options...
Mike C Posted May 14, 2002 Share Posted May 14, 2002 An intermediate step and a little cash, but I would have an O2 bung installed and get an AF ratio gauge and sender. That way you are not guessing at what the problem is but can identify it precisely and at what rpm so you know which circuit needs rejetting and by how much. Here is a good page for info on Weber jetting: http://members.aol.com/dvandrews/webers.htm Quote Link to comment Share on other sites More sharing options...
RedNeckZ Posted May 14, 2002 Author Share Posted May 14, 2002 The problem only happens when I am just sitting with no load on the engine (idling). After it starts to move it runs great (off idle). I have got the books for webers and if I am reading it right. It says to move it to a 52F size. Just trying to make sure I am doing it right. The cost of jets for them are kind of high and I wanted to get it right the first time to save some money for other parts. If you know what I mean. The idle system is the problem and I really want to thank-you for the help. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted May 16, 2002 Share Posted May 16, 2002 IF I remember my weber days, you are going to have to increase the idle jet for the change in air density. I would also be concerned about your main jet too. Might be wise to go up to the next larger main jet, and increase your idle jet. It has been so long since I have fooled with webers. I assume it is popping or spitting a little at idle? That would indicate a lean condition. If are concerned about the funds, you could have an O2 sensor bung welded into you exhaust system, (the closer to the engine, the faster it will warm up and read) and a one wire O2 sensor, and when the car is warm, measure the voltage. Connect the positive to the O2 sensor and the neg to ground. You want to see .45 to .5 volts, which is pretty much stoichometric, you want a little more richness than that at full throttle, but if you get into the .8 range, you are way to rich. You should be able to get a Bosch sensor for an 83 280zx, and use it. They should be about 30 bucks or so. I would not bother getting one that has the connectors, just get the one with a bare wire. BTW I know I didn't say this specifically, but higher voltage means rich, lower means lean. IF you play with it a little, you should be able to quickly diagnose a fuel delivery problem in the future. I have a AFR monitor, and IMO, not worth the money. Take a voltage reading and go. Good luck. I think the 52, if larger(I cant remember) is probably a fine choice. I never changed mine when I had 40 DCOE's, even though I went from a 28mm to 36mm choke. It didn't like the 36's to much, but it dealt with 33's just fine. I think I had 45's. Not sure. I sure do miss the sound of those webers though. Nothing sounds sweeter than a high compression Z motor with a big cam and some webers. Quote Link to comment Share on other sites More sharing options...
Mike C Posted May 17, 2002 Share Posted May 17, 2002 The Nordskog AF ratio gauge from Summit is only $29. Seems indispensible for tuning a carb. Add the weld in bung and a parts store O2 sensor and you can do it right! Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted May 20, 2002 Share Posted May 20, 2002 well if it is only 29 bucks, then it probably wouldn't be a bad investment. I have the ATR one, and it is not worth the money. Quote Link to comment Share on other sites More sharing options...
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