That 600 is holding a 460"er back IMHO, you should be able to gain some throttle response and top RPM with the larger carb, think of it like opening the throttle more...More fuel and more air = more engine speed (theoretically anyways), I would go with the grande Carb.

GT

skee,
I am probably gonna take some $hit for this but bigger is not always better (like I been tellin my wife for years...)...that being said a 460ci @ 5,000rpm will only pull in 666 cfm. of air/fuel...ever.  And it will only pull that much if your engine has 100% volume efficiency.  Most engines are in the 80% category.  Smaller carbs matched to engine/rpm meter fuel more efficiently, offer the best throttle response and low speed torque, that why quadrajet primaries are so small.  Over carbureting an engine dumps raw fuel into the cylinders, washing the film of oil off the cylinder walls, going past the rings and diluting the oil, and at 5k rpm, you want your oil pure and undiluted.  If you need more fuel, jets are the solution.

my.02
P-jet


Thank's...This is kinda the answer I was lookin' for...I have been told it is the OEM carb with the boat,so you'd "think" Spectra knew what they were doin' when they put that carb on "that" boat Anyway to the other guy's..I have checked prices different places..Kinda normal for a Holley Trick Kit for that "list number".. Found a Borg-Warner kit,which I was told was OK to use for $70. I think I'm gonna to the o-haul and give the boat a try...If I dont like it than I will pull the 780 off my Challenger and try that one....Thanx for all the input Guy's!                                                                                 Tracy 


   

skee,

Spectra did not pick the carb for that engine, Ford did.  It came on all the 460 Marine engines.  And as with any mass-produced part, compromises are made in the interest of high production numbers, cost cutting measures, profit margin, etc.  As far as what the engine is capable of, I assure you the engine likes more carb.

There are no formulas that pinpoint the "best" carb for a given engine combo. A bigger carburetor will make more power, a smaller one will offer better fuel economy...no-one should need a carb-expert website to figure that one out.  Most mathmatical formulas that I see get more and more meaningless as you build your engine up; "real world" is not part of the formula's equation (fluid dymanics, air pressure, etc, are not accounted for).  Nor will a carburetor that is "too big" be cause for washing rings.     (A poorly adjusted carburetor may wash rings.) And is there really such a thing as over-carburetion? Meaning, if I compeltely remove the carbs off an engine and pour gas down the intake manifold and then turn the key, won't the engine start and scream? Hell yes it will; it will not tell me that it is getting too much air.  I have even personally run engines without the carburetor installed (or any other air/fuel mixing and metering divices on them), by using a gas soaked rag covering the intake manifold while I raise & lower the wadded-up rag from the carb flange so as to change engine rpm.

If your carbs needs are for a pleasure boat, then a 600 cfm carb can work fine.  If you want more power, then get a bigger carb.  In your case it's that simple. You could try a 750 or 850 cfm.  A Holley 850 cfm has mechanical secondaries, so you can troll around on the primary circuit (like a 2-barrel carb) while still getting very good fuel economy, and also have the secondaries available for the full 850 cfm which would really wake up that 460 of yours, should you need the additional power.  Is the 850 cfm too big? Well, put vacuum gage on your engine while at wide open throttle and you will see that it can handle more carb yet.  Just depends on what you want. 

LO