[Gregski]

Some old timers say that the most common mistake is over carbing your engine, so I am just wondering if you can build a modest streetable 300 horse power 302 V8 engine under a two barrel carburetor, or do I need to be looking for a four barrel?

I have the Motrocraft 2150 carb on mine with the 1.21 venturi size which crresponds with 351 CFM according to this chart, but they go up to 424 CFM.

These numbers are for 2V carburetors only (2100/2150). The first numbers are the Venturi Size, the second is the corresponding CFM.

.98 = 190
1.01 = 240
1.02 = 245
1.08 = 287
1.14 = 300
1.21 = 351
1.23 = 356
1.33 = 424

[YAHAHA]

Yes, this can be done very easily by running a 4-barrel carb. Let's think about this for a second. A 4-barrel is basically a 2-barrel until you romp on it. So techinally, a 4-B is a 2-B until you need a 4-B.

[78stang2]

424 Cfm is a little small for anything over 300ci and judging from the old theory, a well built engine with out exotic parts makes 1hp per ci. Your engine would have to be around 300Ci and your carb would really be starving the engine. Is it possible sure, but if you pulled the 2 barrel off and put the 4 on expect that 300hp to be more like 325 hp or more. On a regular street 302 meaninging (9:1 compression or lower, decent iron heads, a good towing cam, long tube headers, 2.5 inch ID exhaust, electronic ignition with an MSD box) youll be around 300 Hp easily and have good street manners, nice bottom and mid range torque and your power will fade off around 5500 rpm. A 500 Cfm 4 barrel preferably the Edelbrock carbs will be closer to what you need, itll stay in tune a lot easier then a Holley, and yield decent power and economy. Anymore CFM and youll be getting close to over carbed, unless you start doing head work, raising compression high, running big primary tube headers, spinning over 6k rpm and a large diameter exhaust.

[67svtstang]

Depends whos dyno you are using and/or who is blowing smoke up your rear.
If you want 300 hp to the wheels out of a 302, then you will need top of the line cylinder heads such as AFR, a good flowing port matched 4 barrel (dual plane for street driving) intake, good headers, around 10:1 compression, a cam with good lift and the correct duration to match your components, and a 4 barrel carb to match-i would think around 600cfm minimum. You will never build power with a 2 barrel carb and intake. Anybody who says you will is full of it or simply does not know what they are talking about. And i disagree, even though 78stand did say old theory, that a well built engine makes 1hp per cubic inch without "exotic" parts. That might be true for old school ways of measuring hp at the flywheel with zero accessories bolted on and long tube headers, but no way that holds true by todays standards. I have seen way too many factory built engines, small and big block, that had their horespower rated at the same or above their cubic inch diameter, put out pathetic numbers on today's dynos. Just think about the 302s that ford was putting in the mustangs from 89-95. They were well built fuel injected engines with good cams and decent iron heads and they put out around 250 flywheel hp, on a good day.