THAT1_S30 Posted October 6, 2010 Share Posted October 6, 2010 I just got these roundtop SU's for my Z, they were on a L28 and worked fine, until i put them on mine. The car used to start up just fine, idles smooth, pulled hard on acceleration, then over a few weeks it started to idle rough like it had a cam on it, sluggish on acceleration, almost no power, and backfires like crazy when i lightly step on the throttle and dies. I tried tuning them adjusting the knobs on the bottom of the carbs, but doesnt seem to work at all. My car currently sits in the garage and does not start at all. A little help please? Thank you Quote Link to comment Share on other sites More sharing options...
JSM Posted October 6, 2010 Share Posted October 6, 2010 Check your spark plugs first, since you swapped from different motors settings may have been richer and fowled the plugs. Quote Link to comment Share on other sites More sharing options...
THAT1_S30 Posted October 6, 2010 Author Share Posted October 6, 2010 Check your spark plugs first, since you swapped from different motors settings may have been richer and fowled the plugs. I checked them and they have a lot of carbon deposits on them. I cleaned them up and double checked the gap and still doesnt start up, even when i lean up the carbs a bit and sprayed starting fluid in them. Ill go get some new spark plugs and see what kind of result ill get. Quote Link to comment Share on other sites More sharing options...
goodoldjam Posted October 6, 2010 Share Posted October 6, 2010 (edited) Are the carbs a newer rebuild? What it is alot of the time it's a vacuum leak and in my case and alot of others it's a leak at the throttle shafts. Basically you have to tune it very rich if that's the case or it pops. If you can get it running take some starting fluid and spray it around the shafts and see if you have a leak. Could be that they're more worn then you think, I've seen the same thing. SU's seem to run good on one engine and then you figure out you can't get them tuned. Only other major problem I've had was the distributor, Vacuum advance leaking or the plastic bearing guide breaking. I have only found one distributor from a junkyard with a working vacuum advance. I ended up locking the vacuum advance on my old engine. Edited October 6, 2010 by goodoldjam Quote Link to comment Share on other sites More sharing options...
THAT1_S30 Posted October 7, 2010 Author Share Posted October 7, 2010 Are the carbs a newer rebuild? What it is alot of the time it's a vacuum leak and in my case and alot of others it's a leak at the throttle shafts. Basically you have to tune it very rich if that's the case or it pops. If you can get it running take some starting fluid and spray it around the shafts and see if you have a leak. Could be that they're more worn then you think, I've seen the same thing. SU's seem to run good on one engine and then you figure out you can't get them tuned. Only other major problem I've had was the distributor, Vacuum advance leaking or the plastic bearing guide breaking. I have only found one distributor from a junkyard with a working vacuum advance. I ended up locking the vacuum advance on my old engine. The carbs have never been rebuilt. Ill do what you advise in the morning if i can get it running and ill let you know, but as of this moment it still doesn't run, it will just turn over and sputter. If i cant get it running ill borrow carbs from a friend and ill work from there. Quote Link to comment Share on other sites More sharing options...
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