Holley Carb tuning question

« **on:** July 03, 2012, 04:38:45 PM »

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.

« **Reply #1 on:** July 03, 2012, 04:56:35 PM »

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

« **Reply #2 on:** July 03, 2012, 06:18:23 PM »

Make sure the idle speed isn't set too high. Idle mixture screw adjustment goes out the window if the throttle plate is open.

« **Reply #3 on:** July 04, 2012, 08:19:25 AM »

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!

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

« **Reply #4 on:** July 04, 2012, 11:49:03 AM »

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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stc315

Holley Carb tuning question

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