dream240z Posted February 21, 2016 Share Posted February 21, 2016 How are you all doing today? I own a 1970 240z I have a weird problem, I have changed and cleaned everything on this car and she runs very very strong, she warms up great drives very very strong but if I drive even half a mile then idle for a while, like to order a coffee or sit in a drive though, then the carbs gurgle extra fuel into the intake and bogs her down. Once I start driving again there is hard jerking cause from the excess fuel but once I burn it off she is back to being strong. But I just don't trust it. I've cleaned all the internal components to the carbs but was sent the wrong needles so those and the float bowl needle valves were not replaced. Other than that idk what's going on. Any ideas? Quote Link to comment Share on other sites More sharing options...
seattlejester Posted February 21, 2016 Share Posted February 21, 2016 Have you checked your idle speed and mixture? Are the carbs balanced? Are they factory carbs? Are you running a lot of choke? Lots of questions there. Sounds like it needs a tune up if it otherwise runs fine. Probably need to change the plugs and lean out the mixture screws so it doesn't bog while sitting. If you can get an AFR gauge you can set it so that the car idles above about 10AFR, below that is when it starts to stumble and choke on itself. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 21, 2016 Share Posted February 21, 2016 Follow the procedures in the FSM to tune the carbs. Quote Link to comment Share on other sites More sharing options...
dream240z Posted February 21, 2016 Author Share Posted February 21, 2016 Running no choke when problem occurs, stock carbs yes, they are balanced, and I don't have and AFR gauge but I'll try just leaning it out if you thinks that's all it is. Quote Link to comment Share on other sites More sharing options...
Miles Posted February 21, 2016 Share Posted February 21, 2016 Go to Z Therapy and buy the video "Just SUs". You are going to need it. http://www.ztherapy.com/ Quote Link to comment Share on other sites More sharing options...
seattlejester Posted February 22, 2016 Share Posted February 22, 2016 Don't just lean it out per say, that is not a good idea. The mixture screws control the entire range, so leaning them out too much on the bottom can make the car run really lean on the top end. You can follow john's advice and do the base procedure as in the FSM to get you a factory baseline. Once you get an AFR setup you can play around with it till it feels right. Quote Link to comment Share on other sites More sharing options...
Miles Posted February 22, 2016 Share Posted February 22, 2016 If your mixture adjustments are reasonably close you may want to consider other reasons for flooding: Float adjustment, Verify float level is set to factory specs. Sticking/stuck needle valve. Fuel level in bowel set to match top of jet. If fuel level in the bowel is higher than the top of the jet fuel will just drain out through the jet! There is a procedure for checking this using a clear plastic hose. Quote Link to comment Share on other sites More sharing options...
dream240z Posted February 22, 2016 Author Share Posted February 22, 2016 So apparently I believe it was as simple as being to rich, I leaned it out, and ended up getting better idle and better performance at all rpm I didn't think it would be that simple but when I cleaned the carbs inside and out I checked all other causes and everything else looked good. It it as always was user error. And that's after paying 2 Seattle shops to do it for me, they both failed miserably Quote Link to comment Share on other sites More sharing options...
seattlejester Posted February 22, 2016 Share Posted February 22, 2016 Not too many shops here are still familiar with carbs, especially side draft carbs. Quote Link to comment Share on other sites More sharing options...
Miles Posted February 23, 2016 Share Posted February 23, 2016 Go to Z Therapy and buy the video "Just SUs". Watch the video a few times and the SU carb will be very easy to tune and work on. Quote Link to comment Share on other sites More sharing options...
beermanpete Posted February 23, 2016 Share Posted February 23, 2016 Could be a vapor lock probelm. Quote Link to comment Share on other sites More sharing options...
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