BTF/PTM Posted April 2, 2010 Share #1 Posted April 2, 2010 What's the difference? My '72 currently has 3-screw SU's on its L28, and the second engine I have (F54/P90) has 4-screw SU's on it. Oh, and I'm referring to the number of screws holding the domes in place. Link to comment Share on other sites More sharing options...
Bruce Palmer Posted April 2, 2010 Share #2 Posted April 2, 2010 3 screw carbs and manifolds has provision for water into the carb body for extra preheat. Link to comment Share on other sites More sharing options...
Bonzi Lon Posted April 3, 2010 Share #3 Posted April 3, 2010 How about this one?The dealership replaced my flat tops with new round tops in 1980. After learning what these carbs are, I noticed mine has a 4 screw for the front and a 3 screw for the back. They work fine, just odd.Bonzi Lon Link to comment Share on other sites More sharing options...
ajmcforester Posted April 3, 2010 Share #4 Posted April 3, 2010 My 4 screws have water heating Link to comment Share on other sites More sharing options...
Diseazd Posted April 3, 2010 Share #5 Posted April 3, 2010 Maybe Bruce "screwed up"! Link to comment Share on other sites More sharing options...
Bruce Palmer Posted April 3, 2010 Share #6 Posted April 3, 2010 Maybe Bruce "screwed up"! Now, cut that out!! nyuck nyuck...... Link to comment Share on other sites More sharing options...
ajmcforester Posted April 3, 2010 Share #7 Posted April 3, 2010 Their isn't much difference from what I heard about the 3 or the 4 screw carbs, other than the screw patterns. I don't know but I'd bet you could use the pistons in the dash-pots interchangeably and a lot of other parts, I bet Bruce would know if that was the case. Link to comment Share on other sites More sharing options...
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