SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: stc315 on July 03, 2012, 04:38:45 PM
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Running vacuum secondary 750 Holley. Playing with the idle mixture screws does nothing what so ever. I can't remember if I need to jet up or down? I'm thinking it is up considering these carbs are usually tuned for small block. Otherwise the thing is running pretty good. But I know it can run a little better.
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I have the same carb on my bbc, I never changed the jets, just dialed it in and it runs great, I do have a stock 454 thou
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Make sure the idle speed isn't set too high. Idle mixture screw adjustment goes out the window if the throttle plate is open.
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Crewcheif is the Holley expert I call on with these things. But is that carb the one that came on the boat? If it is, it should be a marine 4160, and if it isn't, you need one if you kept the "Eiffel Tower" of engine covers on that thing, Sammy! :sly: AT that point, I'd be shopping for an 850. 460's LOVE 850's like "Mongo Like Sherrif".
The idle mixture screws, run them in, back them out 1 1/4 turns, leave 'em be. Who idles anyway? The jets? Need solid plug readings to be sure, but typically, I find #86 in the primary and #92 in the secondary seem to work out very well more often than any other combination. This is on 750 carbs. Would need to step up a size or two on an 850.
Ray
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Ray, it still has Mt. St. Baker on it. Definitely not original carb. I want an 850, just can't afford one right now. This carb comes from factory with 72s in primary. It actually works pretty good but plugs look a little lean. Porcelain is fairly white. Not creme color like it should be. On a note, I am running 30% race gas, 70% 91.
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