Guest 240hybrid Posted December 1, 2002 Share Posted December 1, 2002 I was wondering if there would be any difficulties/problems with swapping nondomed/flat topped SU's off a late 260 onto a 240 motor?? The SU's are model number HMB46W....these are the flat top ones. Will they mate up to 240 intakes without mods. and are they easily tuned?? I dont see why this combination wouldn't work, just want some input on subject, I know a guy interested in this swap. Quote Link to comment Share on other sites More sharing options...
Mike C Posted December 1, 2002 Share Posted December 1, 2002 Why? Usually the first mod somebody with flat tops does is pull them off and swap on round tops. They will work, but they aren't near as good or easy to work on as the round tops. Quote Link to comment Share on other sites More sharing options...
Guest 240hybrid Posted December 1, 2002 Share Posted December 1, 2002 HA I would have figured that the later ones would be prefered, guess not. What exactly makes them more of a hassle....just getting air/fuel right, or synchronizing? I'll let him know that the domed top, which he'll probable go with, are better suited for what hes got. Hell its a 240, put 240 carbs on it. Quote Link to comment Share on other sites More sharing options...
Guest Z-rific Posted December 1, 2002 Share Posted December 1, 2002 The flat tops were designed with emissions and fuel economy in mind. You can do a lot with round top SU's. If you have some cash, you can send them out to Z-Therapy who will modify them to hi-po standards. You can also get larger needles for em to get more gas if you do other mods and need more gas. With a basically stock engine, a well tuned set of SU's is all you really need. For a dramatic and sexy carb mod, look into getting some triple Webbers (again, only really needed with engine mods). But theyre $$$$$. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted December 1, 2002 Share Posted December 1, 2002 The flat tops were emission carbs and reported ran like s**t and tended to vapor lock. Swapping them out with early SU's is what everyone does. The early SU's are sweet carbs and probably give the best overall mix of performance, economy and drivablity. Can be a little expensive to rebuild properly since the 20+ year old carbs develop vacuum leaks through worn throttle shaft bushings. Quote Link to comment Share on other sites More sharing options...
Guest 240hybrid Posted December 1, 2002 Share Posted December 1, 2002 I'll tell him that their not work a damn. unless he's going for fuel economy and emissions.... dont think so. Thanks for the input. He wants the domed tops I think. thought I'd ask around. Quote Link to comment Share on other sites More sharing options...
Guest bang847 Posted December 3, 2002 Share Posted December 3, 2002 i have heard of people making the flat tops run good but... why?? basically i heard you need to strip thme down back to a SU style... but still i think these are not completely driven by a true venturi action... those dome tops are great.. dont let go of them... if you got no cat... you can tune these to run generally rich... Quote Link to comment Share on other sites More sharing options...
DAW Posted December 8, 2002 Share Posted December 8, 2002 The only good thing about the 260Z carbs is the butterfly plate choke vs the sliding mainjet mechanism (which can stick) of the 240Z round top carbs. Otherwise they are an overly complex, poor performance, vapor-locking carb. DAW Quote Link to comment Share on other sites More sharing options...
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