Inliners International Forums General Discussion Engines GM 250 inline 6, which carb?

I'm getting ready to pul the trigger on an Offy intake manifold and Langdon cast iron headers. Between the Holley 390 and Edelbrock 500(1403) which will be the better driving of the two/easier to tune. Which is closest right out of the box?

Thank you!

390 holley with vac secondarys. 500 is too big imo

What kind of car is it going into? Is there any other work done to the engine or is it a stock 250?

Just a few questions to narrow it down for the professionals on here

I've had better luck with Edelbrock carbs being "start and go" than Holley, but the Holley will always be more adjustable.

I have had good luck with the Holley 390 list 8007. Maybe a jet change for mileage,

Stock 250 motor, Offy intake, Langdon Cast iron headers, HEI. Maybe a cam swap next year. Appreciate the recommendations.

STOCK ENGINE NEEDS A STOCK CARB OR IT WILL SUCK THE GAS WORSE THAT A SMALL BLOCK.....

I agree w all the above except:

Bcowanwheels: I disagree about the mileage (but agree about John 3:16)

I tested a bunch of 4bbl carbs on a stock 250, Nova powerglide 3.08. Overall average MPG for the 4bbl carbs was BETTER than for the Rochester B/BC/BV carbs. Only about 5% or 10% better but still better.

As far as performance, I clocked 60ft-330ft-660ft.


My formula for CFM is "double your horsepower". Thats the CFM you want at 1.5" Hg, the 4bbl style rating. A little less with a heavy car or tall gearing. So for a stock 250, plus 4bbl, plus exhaust, you should have 170-180hp so you want about 350cfm. Only the old Ford Teapot (aka Firebox) and a few others are THAT small. Otherwise, your closest bet is the 390 Holley, the one Tom Lowe noted. If you plan to build a SERIOUS 250cid, its too small, but with just carb, exhaust, maybe small cam, its about perfect.

I also tested a 450 Holley that ran so close to the 390, I'd go with whichever one I got a better deal on.

That said, in my testing, the 600 Edelbrock gave the little Holleys a good run, even besting them in some of the testing. Such a HUGE carb? What I think was happening was, the 600 Ed was just using its primaries and the secondary transition circuit, so it was more like 300cfm total.

In my testing on v8s, the secondary of the AFB will not keep pace with the Holley secondary, it will give up a carlength or two in the 1/4 mile.

I didnt have a 500cfm Edel / AFB to test, that would have been getting part way into the secondaries.

Holley carbs are notorious gas hogs at light throttle, so I would bet on the 500 Ed/AFB for better mileage, but not by much vs the little 390 Holley if jetted right as Tom says.

Get whichever one you score a deal on, 390 or 450 or 500.

thank you for the insight! much appreciated!
I'm partial to the Carter(Edelbrock) type carbs. Many years ago when I switched from a Quadrajet to Carter AFB I did notice a drop in performance so I agree with all on that.

Never have run a Holley(go figure), that 390 sounds like one good little carb.

Anyone have any info on Clifford Performance 2 barrel Weber setup?

Larry at Clifford says they are the best thing since sliced bread. He brags about the big torq outputs too. I am spectacle and would like to see proven results. He also sells the carbs, go figure.

This is a little tougher than I was hoping. All I'm really looking for is a great daily driver with a little more power. No temperamental teenager, although I'm not afraid of fine tuning in the least.

I believe Tom Langdon sells the Weber carbs too, ohh brother!

update: I decided to go with the Clifford setup intake, weber 38, shorty headers. Hope she's a nice driver.

Post results...

Pleaseee

will do, hoping for a very nice DD. going to keep stock valve train in for now. Would like to compare before and after with a healthier cam installed.

Does anyone have any insight/opinions on the water choke the Weber Carb uses vs a more typical electric choke?