So i tried a holley 600 on my 250 would idle but not run bogged and died so........ I ordered a holley 390 and some full length headers gonna put them on this weekend. Any advice you guys gould give?

What intake are you using? Is it heated with water or exhaust?

Why not spend some time tuning the 600 before scrapping it for a different/new carb?

Was the carb working like it should???I have ran a 600 on my Stock 250 and never had any issues with it. And i ran it for many yrs on a mildly built 250 (just a RV cam).Then I used it for a vary short time on my well warmed Over 250, Before going to my dual cliford with dual 450s Then to my 3x4 tunnle ram.

So If it was me I'd make sure the carb was in top shape before spending the money on another carb.

PS and I never had any type Of heat Other then the heat comming off the headers.Even in 40 deg. Fla weather.

ofenhauser heated with the stock exhaust

also i should add it has a mercrusier cam in it

to be honest i put the carb on wich is a summit 600cfm and set the floats and thats it. I have never tried to tune a carb before I guess I have always been lucky bolted them on and they worked. All of my experiance has been in sbc's this is my first inliner.

If you were to learn how to tune/adjust carburetors you would never be sorry for having spent the time learning to do so. The theories and principles involved allow you tune your car for your specific needs/wants/circumstances/requirements no matter how unique. Being able to do so yourself means you are not at the mercy of ANYONE else and it is extremely satisfying.

Besides,no new carb out of the box will be perfectly tuned for your application with out SOME dialing in. While carburetors might be becoming more and more obsolete, the theories behind them are not; their principles directly relate to fuel injection.

Heck, if nothing else, by tuning your Holley 600 to your liking, you would therefore have the money that you spent on the 390 to buy other goodies.

Fasteddie is 100% right -- performance comes from tuning not just parts. You can eke out performance and mileage both from whatever parts you have. Nice parts, bad tuning, make for trouble.

Carbs are tricky, but learnable. Each carb type (Holley, Weber, etc) has it's own design and foibles. There's aftermarket books on each. Get one, spend a few hours under the hood and tune up what you've got.

Once you get the hang of it, you may achieve some Enlightenment and begin to understand your engine from First Principles -- eg. not just how much to turn a screw, but *why*. This knowledge will also help you problem solve too.

Whatever mechanicals you've got in there, assuming they're in decent operating shape, master carb and spark and you'll wring all the performance available from that particular pile of iron.

You'd be surprised what good tuning will accomplish. No amount of fancy product will fix bad tuning.

I recommend a wide band O2 reader.

It will tell you exactly if you are running to rich, too lean & everywhere else.

Get the best A/F ratio for mileage.

It will tell you if you have too much accelerator squirt etc.

Having a WB reader really speeds up the tuning process & takes the guess work out.

For the most part, you do not need to take out your spark plugs & try to read them.

They are affordable & no good reason not to have one.

MBHD

The best A/F for mileage will take a while, because the amount of vacuum advance must be (at least) roughed out before trying a mixture test.
Don't be surprised if the best mileage comes from +15° on advance and 16:1 (not 14.7:1) ratio.

Yes this. I run the cruise mixture a lot leaner than most guys it seems on a moderately tuned engine such as a 302 GMC or 261 Chervy with about 9-1 compression and a cam with 215 degrees duration at .050 lift.I jet down the mains until the engine hesitates at slight acceleration in high gear at about 45 mph.Then jet up a touch. Running about 20 crankshaft degrees of vacuum advance and about 20 degrees of mechanical at that road speed.Heated intake with a 180 degree thermostat. The plug porcelain will generally be dull white.The light tan color is usually too rich at a light cruise engine load.
There's many variables here depending on engine tune and gearing ,the carb can be still running off the idle transition circuit at 1600 rpm with the main jets coming online around 1700 rpm.Engine temperature,heated intakes,fuel octane,compression and combustion chamber design and quench all affect the jetting.And messing with the main jets affects full throttle mixture as well .And few engines may have better fuel mileage with a slightly richer jetting that I aim for.
Trial and error is the only way. And for sure an A/F meter is very useful.