Using a carb that’s too big?

my 306 ran high 10's with only a 650

Just adjust your throttle linkage to only open the carb 3/4-way - then you'll only have 600cfm....

There's no such thing as a carb that's too big.....

Think about it. What happens when a bone stock 302 is wide open throttle, and running about 2500 RPM? It only needs just a little bit of airflow. So if the carb is 500 CFM, then it's too big

there's a hell of a lot more to a carb than it's CFM size. Just as I stated before...I ran 1050's on 302's for years with great success. They sure looked weird though. The carb was as wide as the rest of the motor. You CAN tune the carb FOR the motor, but generally they're pretty close right out of the box. notice I said GENERALLY. I've seen/had some Demons among others that were so far off of a tune that they would run like poo on anything but a lawn mower.

I say bolt that sucker on there & go drive it. I think you'll be surprised how well it will work.

I remember talking to a guy who had a 302 built and dyno tested by Superior Automotive here in So Cal (a very good shop). They tried several different carbs from 600 to 830 cfm on the 302 which had Edelbrock RPM heads. The 830 resulted in the most peak power (413 HP or something like that) by some 15+ HP.

Take it for what it is worth...there may have been other factors involved such as jetting...not sure.

I've got a 780cfm on my 289... 800 on a 351 should be fine.

As the other said, you might run into driveability issues... and you might not, it just depends on the tune of the carb. You will most likely loose some mileage though, because most of the time the Holleys are rich on the idle and transition circuit, which is what you will be running on most of the time with an 800 on a mostly stock 351. I think they calibrate them rich because most engines will DRIVE just fine rich, no hesitation or surging... they'll just get crap for economy... but if they're lean, you can run into all sorts of driveability issues.

I ran a 850 mighty demon on a stone stock super high mileage 81 302 engine, I had to run VR1 20-50 in it to keep the bearings from knocking, and only had 20 psi max pressure at wot. It worked fine, I even sprayed 5 bottles through it at 175hp shot. It ran stronger on the motor after the first few nitrous runs. Who would have thought.

I ran a 750 on my 289 for a while. It ran rich but I didnt ever jet it. I ran a 625 after it and it didnt make more power, it just ran better. Blkfrd did you mean superior automotive in Santa Barbara?

You can use most any carb you want if you are willing to tune it to the application. Proper carb sizing goes along with the volumetric efficientcy of the engine and the related drive train modifications. Say you put an 800 CFM carb on a stock engine and drive train just because it fit. When you stab the throttle the airflow into the engine slows down at low rpm. This causes a lean condition of which he accelerator pump shot adds fuel to cover it up. This is why you get backfires when suddenly opening the throttle.The air has to be moving sufficiently to create a vacuum signal at the venturi booster for flow. Change the rear gear ratio to say 4.11 or 4.88 and the resistance to moving the vehicle drops. Now the engine can rev faster and of course the air flow will pick up faster. You have to now reduce the accelerator pump shot accordingly. Why do you think Edelbrock offers basically 2 CFM ratings on their carbs? They are the most popular to cover most applications. Granted they can't be modified like a Holley for added airflow but they can be tuned very precisely without spilling fuel all over. Holley finally realized that the main body of their carb should be made without an airhorn and are producing higher flow carbs with old sizing on the venturi/throttle plate. If you do decide to go bigger make sure you get the annular booster venturi. They were initially designed for the model 4180 truck series carb for Ford. We couldn't leave well enuff alone and started testing them in higher flowing carbs where they weren't designed to work. We found the restriction and fixed it. They did cut down the airflow but modifying the main body for optimum airflow brought it back up.

I dont know on his carb but I believe the two barrel on the 82 GT Mustang had a 525 2v if my memory is correct.