Guest Anonymous Posted August 17, 2002 Share Posted August 17, 2002 I have a '73 Z with the dual flat top carbs which I hear aren't very good... but either way, when starting the car, it idles very rough, when the car revs at about 2000 rpms, it starts backfiring and choking very hard. Just had the head done because one of the cylinders lost pressure due to broken seals, so the head is not the problem. Has a brand new distributor, timed, and points set correctly. Any ideas as to what my problem may be? Thanks Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted August 17, 2002 Share Posted August 17, 2002 try taking the belt off of the smog pump Quote Link to comment Share on other sites More sharing options...
Mike C Posted August 17, 2002 Share Posted August 17, 2002 Does it just do it cold or when warm also? Spitting out the carbs is a sign it is running too lean. My air pump would cause the car to pop in the exhaust on deceleration and gear changes, but not to spit out the carbs. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 17, 2002 Share Posted August 17, 2002 When the car starts up cold, it idles very very rough, I have to keep the gas on to prevent it from dying. Once it gets warmed up, it idles at about 1000 rpms, but spikes and sags a lot, but does not die. Once you apply some gas to it, it starts backfiring hard. But yeah, to answer the question, it backfires cold and warm. Quote Link to comment Share on other sites More sharing options...
Mike C Posted August 18, 2002 Share Posted August 18, 2002 Alos invest in a UniSync to tune the carbs. Get a tuneup book and adjust the carbs correctly. You may want to pull them off and put new gaskets and make sure the floats and needle and seats are OK. Victoria British has carb kits for $15 each. Not the best, but suffiecient for a rebuild. Quote Link to comment Share on other sites More sharing options...
Guest sehlers Posted August 18, 2002 Share Posted August 18, 2002 Hey Reiner , My advice after working on only Datsun / Nissan cars , and specializing on Z cars in my business for 28 years , is to get rid of the original carbs ! After doing Hundreds of conversions over the years , this will be the inevitable , if you want a good running 240. Quote Link to comment Share on other sites More sharing options...
aviatorx Posted August 18, 2002 Share Posted August 18, 2002 ...what kind of oil are you using in your carbs?...seems to me that the carb pistons are hanging up with either no oil or too high a viscosity..... use either a 5-30 / 10-30 weight ...a lower viscosity oil will allow the carbs to respond faster but will leak down into the intake and burn. You may also have air leaks at the throttle shaft or gasket area(s) but check the damper oil first, then for air leaks, then idle mix adj screw Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 19, 2002 Share Posted August 19, 2002 Thanks everyone for the advice and possible solutions to the problem I have. I'll look into all of them and see what the problem is with the carbs. And as to replacing the carbs, I was thinking about getting a conversion for the manifold and converting it to single carb and throwing a Holley 390 CFM 4-barrel carb on there. Do you think that would give me better performance as opposed to sticking with dual-carbs? I hear a lot of discussion as to which is better, but hopefully someone can give me some ideas here. Oh, and I think that it may be the oil that is causing the problem, combined with the leaks, when the car is running, the exhaust is pretty heavy with smoke and something worth mentioning, you can smell gasoline coming from the carbs pretty strong, leading me to believe that there may indeed be a leak. Any input? Quote Link to comment Share on other sites More sharing options...
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