XCYTER Posted February 11, 2008 Share Posted February 11, 2008 So from all that I have read I would like to get something straight. The mixture nut on the bottom of the carbs ONLY affects the idle correct? At speed the only thing having affect on mixture is the needle and guide for the needle. One of the moderators here posted that and I am trying to understand it. ....and also the balancing screw on the linkage for the two carbs- (at cruising speed) I ask this because Ive been fouling plugs non stop and only until I screwed the mixture nuts all the way up does my car run great,, worn needle and guide!!! ------SO in theory you could have the most worn carbs around and as long as you can get your idle good even if you have to screw the mixing nuts ALL the way up, then your good- right? ..and of course set the floats. Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted February 11, 2008 Share Posted February 11, 2008 So from all that I have read I would like to get something straight. The mixture nut on the bottom of the carbs ONLY affects the idle correct?At speed the only thing having affect on mixture is the needle and guide for the needle. One of the moderators here posted that and I am trying to understand it. ....and also the balancing screw on the linkage for the two carbs- (at cruising speed) I ask this because Ive been fouling plugs non stop and only until I screwed the mixture nuts all the way up does my car run great,, worn needle and guide!!! ------SO in theory you could have the most worn carbs around and as long as you can get your idle good even if you have to screw the mixing nuts ALL the way up, then your good- right? ..and of course set the floats. If it was that easy no one would be asking questions about them. No matter what adjustment you make it will effect something else. Most likely the reason that your car runs better with the nut screwed all the way up is because you have a huge vacuum leak at the accelerator shaft (the shaft that the butterflies are mounted in) this will cause enough air coming in down stream from the needle and jet to offset the air/fuel adjustments made with the jet adjustment nut. Probably the best place still yet to get information on the SU's is from Ztherapy, if you can not find enough on their website give them a call or better yet purchase thier video of how to set up and tune SU's. Dragonfly Quote Link to comment Share on other sites More sharing options...
XCYTER Posted February 11, 2008 Author Share Posted February 11, 2008 If it was that easy no one would be asking questions about them. No matter what adjustment you make it will effect something else. Most likely the reason that your car runs better with the nut screwed all the way up is because you have a huge vacuum leak at the accelerator shaft (the shaft that the butterflies are mounted in) this will cause enough air coming in down stream from the needle and jet to offset the air/fuel adjustments made with the jet adjustment nut. Probably the best place still yet to get information on the SU's is from Ztherapy, if you can not find enough on their website give them a call or better yet purchase thier video of how to set up and tune SU's. Dragonfly I have their video and have watched it 4 times. My question was in reguards to a comment by a moderator that the mixture nut affected only idle and that as you stomp on the gas the needle is no longer seated so the mixture nut then has no affect on the running of the motor. I do agree with you that Ive probably got a vac leak somewhere but have tried carb cleaner and sprayed it around the shaft..didnt notice much change. Im only asking because I need to pass smog and have been pulling my hair out adjusting these carbs over and over... I do plan on getting some Ztherapy carbs soon but have to pass smog by the 25th of this month. Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted February 11, 2008 Share Posted February 11, 2008 When you change the mixture nut on the jet it raises or lowers the jet in relation to the "bridge" in the throat of the carb as well as were it sits on the taper of the needle. Both of the above will have an effect on how the engine idles as well as how rich or lean the engine runs with the engine at partial throttle. Most likely you have several problems with the carbs due to thier age more than anything else. You will probably find that the piston under the dome is covered in a sooty varnish, the air holes in the dome are probably partialy clogged, the balance hole in the body of the carb between the piston and the throat is also probably partialy clogged, the needle may or may not be seated correctly in the piston and if you see any wear marks on the needle then it should be replaced. Carefuly pull the jet and check it for wear at the top edge where the needle goes in at, if you find the hole is out of round the jet needs to be replaced. At the throttle shaft (accelerator shaft same thing) take a small amount of axle grease or similar heavy grease and apply it all the way around the shaft against the body of the carb on both sides of both carbs. Try starting the car and see if that changes the behaivior of the idle and if you have to adjust the idle nuts under the jets. Since you have the video and it does not make since to you to ahead and email or call Ztherapy and tell them what you are encountering and that the video has not been able to help you. One last thing... most likely you will not be able to pass smog with the carbs that you have on the car right now because you will not be able to get them to run well enough throughout the range of the smog test without having a gas analyzer to help you adjust and tune them. I could be wrong on that though because I do not know what the requirements are where you live. Dragonfly Quote Link to comment Share on other sites More sharing options...
XCYTER Posted February 12, 2008 Author Share Posted February 12, 2008 ok it failed smog again today. Not too happy. Im gonna order the SU rebuild kit from ZTherapy,,, I hope it has all I will need. Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted February 12, 2008 Share Posted February 12, 2008 ok it failed smog again today. Not too happy. Im gonna order the SU rebuild kit from ZTherapy,,, I hope it has all I will need. The rebuild kit they sell is a very good and complete kit but it can not replace the worn out aluminum where the throttle shaft goes through the carb(s), that has the potential to cause you to fail smog once again. I would recomend that you talk to them on the phone or by email prior to ordering the kit and let them know exactly what you are having problems with, it may even be helpful to provide them with the numbers from the smog test that way they will be better able to let you know if the kit will acomplish what you want or if you need to purchase "bushed" carbs. The bushed carbs are more money but should probably last you untill the planet runs out of gas as long as you take care of them (of course that is my opinion based on the carbs I got from them and the quality of rebuilding and bushing). Remember part of making a purchase from someone is they are somewhat obligated to answer all your questions for you to the best of thier ability and as truthfuly as possible. So ask them every question you can possibly think of to make you feel comfortable that the purchase you make from them will take care of the problem you are having. Dragonfly Quote Link to comment Share on other sites More sharing options...
XCYTER Posted February 15, 2008 Author Share Posted February 15, 2008 I was curious if anyone here has used the rebuild kit from ZTherapy and if so did you have success? I understand the kit will not correct throttle shaft leaks. I took my carbs off , the shafts arent perfectly sealed but I cant believe that much air could be wizzing by...besides air coming in would only LEAN out my mixture...I just wanna pass smog...grrrrrrrr ...I could put super thick grease over the shaft ends for smog day couldnt I? Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted February 15, 2008 Share Posted February 15, 2008 I would like to see what your readings from the smog test were, that can give a lot of information as to what is causing you to fail. If your smog test are like the ones here the operator is not allowed to tell you anything that can help you as it creates a conflict of interest. I can tell you however that your carbs may may not be the cause of your failing. If you are completely stock and you have changed your plugs to a hotter or colder range than stock it can cause you to fail, if the car is tested with the engine below normal operating temp (usualy 180 degrees) you can fail smog, if you did a tune up with an oil change and an engine flush prior to the smog test it will cause you to fail, if you have a problem with your egr valve, air pump, vacuum lines, or timing you can fail smog, if at some time in the past someone modified the air injector tubes in the exhaust manifold or if you have holes in your exhaust pipe you can fail smog. There are countless other things as well that can cause you to fail a smog test. At this point for you I would recomend that the next bit of money you spend on the car is to have a mechanic that you trust put your car on an exhaust gas analyzer (smog machine not involved in the states smog program) to have it evaluated so you can pinpoint the real problem then you can put your energy into fixing the real problem, because from your discription of the carbs they are in good enough condition to pass. If the carbs do need adjusting the mechanic can adjust them while on his machine and tell you exactly what to do to insure you pass on a state machine. Dragonfly Quote Link to comment Share on other sites More sharing options...
XCYTER Posted February 15, 2008 Author Share Posted February 15, 2008 I failed because I was running very rich and had an intermittant miss. The smog pump is not hooked up and I dont want to go through the trouble and massive expense of making it work. I do agree with you 100% as far as having a mechanic check the rest of things out. I have looked and looked and looked but no one here in Reno works on old SU's and those 2 that do (Nissan and a high perf. shop) both charge HUGE money to correct SU's (more than new ZTherapy carbs). So I was thinking rebuild the carbs, then have a mechanic check dwell,timing etc... and go for it again. I only have a few more weks and then I have to pay the DMV more $$$$. rebuild and some greese??? Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted February 15, 2008 Share Posted February 15, 2008 I failed because I was running very rich and had an intermittant miss. The smog pump is not hooked up and I dont want to go through the trouble and massive expense of making it work. I do agree with you 100% as far as having a mechanic check the rest of things out. I have looked and looked and looked but no one here in Reno works on old SU's and those 2 that do (Nissan and a high perf. shop) both charge HUGE money to correct SU's (more than new ZTherapy carbs). So I was thinking rebuild the carbs, then have a mechanic check dwell,timing etc... and go for it again. I only have a few more weks and then I have to pay the DMV more $$$$. rebuild and some greese??? Your in a pretty tough spot there, depending on the requirements in Reno you may not be able to get it to pass without the air pump hooked up and working but its hard to say for sure. I am lucky in that I have a friend that owns a shop and allowed me to adjust my carbs and tune my car myself on his smog machine (just paid him for the use of his machine) you probably will not be able to get anyone to do that for you because of liability. Most likely the reason the two shops in town charge so much is because they do not know how to work on SU's and are going to charge you by the hour to monkey with something they know nothing about while hoping to stumble into getting it within the requirements. Try getting the car evaluated to pinpoint the problem then if the problem is with the carbs see if you can purchase a tool called the "color tune". With a color tune you can much more acurately set up your carbs on your own without a smog machine but be aware it can be a PITA to use. Dragonfly Quote Link to comment Share on other sites More sharing options...
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