I am getting a 65 Barracuda with a 225 super six. I would like to put a 4bbl on it and have read most everyone uses a 390 CFM carb. I have a 570 Holley Street Avenger I would like to use after a rebuild. Will it hurt the performance of my engine?

Yes. Putting a 570 CFM carb on an otherwise stock motor, especially a 65 motor with the older smaller camshaft will just make the motor fall flat on its face. You really don't need a four barrel carb to get good performance out of a slant six unless you are building a dedicated 1/4 racer.

_________________
Casually looking for a Clifford hyperpak intake for cheap.

Thanks Reed I will get the 2 bbl rebuilt.

I suppose more info is needed. When you say "Super Six" with reference to 1960s slant sixes, you could be referring to someone installing a "Super Six" two barrel carburetor and manifold from a late 70s era vehicle or you could be referring to the "Super 225" which was another name for Plymouth 225 cubic inch slant sixes.

Is your motor a 65 motor with a two barrel carb and intake? Are there any other mods? Is it a complete later motor swapped into the Barracuda?

_________________
Casually looking for a Clifford hyperpak intake for cheap.

Yes it is a 65 225 with a Factory 2 bbl and intake,and 904 trans.I wish it had dual exhaust but it doesn't. I haven't gotten it home and don't know the rear gear ratio.

Slant sixes didn't come with two barrel carbs from the factory in 65, so you either have someone swapping in a later intake manifold and carb or a whole later motor. Slant sixes never came with factory dual exhaust, but you have several options to get there. Frankly, a single exhaust that is between 2 1/4 and 2 1/2 will flow plenty and weigh less than true dual exhaust. There is a small performance advantage to splitting the exhaust manifold into two groups of three (123 and 456) but it is perfectly fine to have the two pipes join back into one.

_________________
Casually looking for a Clifford hyperpak intake for cheap.

The intake could have been switched, but the engine is original to the car. I will get the numbers from the intake this weekend.

I talked with the owner today and he said it was a original 225 /6 but the intake is in question of what year it's from.