Clifford Vs Offy
The Clifford manifold is designed for use with headers only while the Offy 4bbl is designed to bolt up to the OEM exhaust manifold. Although I don't have any experience with the Clifford manifold, my understanding is that its passages are larger and better suited to higher RPMs. The Clifford also includes a provision for water heat, which they recommend for street use.
The Hyper-Pak intake manifold now manufactured by Clifford is a Doug Dutra reproduction. From what I've read about it so far, getting good driveability and/or power takes a bit of work.
On my 65 Barracuda, I started off with an Offy 4bbl intake and a 625 CFM AFB with headers. I found that no matter what I did with the accelerator pump shot, I would always have an off-idle bog. After some research, I found that I could just about eliminate it with a metering rod with an extremely rich power step. The problem turned out to be that my lack of intake heat caused the fuel to drop out of the airstream. The extremely rich power mixture made up for the fuel that puddled on the intake floor when I hit the gas. As a result, I built intake manifold heater to maintain a hot spot underneath the carburetor. With this heater, I experience absolutely no bog with the 750 CFM Quadrajet I'm currently running.
Gasoline produces a refrigeration effect as it vaporizes in the intake manifold. This means that the manifold becomes very cold on an engine with headers right after startup. The cylinder head supplies heat to the intake manifold once it is warm, but this is inefficient because the heat doesn't transfer all that well across the gasket and the heat travels through the intake runners. Ideally, there should be a hot spot under the carb to vaporize any fuel that drops out of the airstream as it makes the sharp 90° turn from the carb to the intake manifold.
The Clifford manifold is designed for use with headers only while the Offy 4bbl is designed to bolt up to the OEM exhaust manifold. Although I don't have any experience with the Clifford manifold, my understanding is that its passages are larger and better suited to higher RPMs. The Clifford also includes a provision for water heat, which they recommend for street use.
The Hyper-Pak intake manifold now manufactured by Clifford is a Doug Dutra reproduction. From what I've read about it so far, getting good driveability and/or power takes a bit of work.
On my 65 Barracuda, I started off with an Offy 4bbl intake and a 625 CFM AFB with headers. I found that no matter what I did with the accelerator pump shot, I would always have an off-idle bog. After some research, I found that I could just about eliminate it with a metering rod with an extremely rich power step. The problem turned out to be that my lack of intake heat caused the fuel to drop out of the airstream. The extremely rich power mixture made up for the fuel that puddled on the intake floor when I hit the gas. As a result, I built intake manifold heater to maintain a hot spot underneath the carburetor. With this heater, I experience absolutely no bog with the 750 CFM Quadrajet I'm currently running.
Gasoline produces a refrigeration effect as it vaporizes in the intake manifold. This means that the manifold becomes very cold on an engine with headers right after startup. The cylinder head supplies heat to the intake manifold once it is warm, but this is inefficient because the heat doesn't transfer all that well across the gasket and the heat travels through the intake runners. Ideally, there should be a hot spot under the carb to vaporize any fuel that drops out of the airstream as it makes the sharp 90° turn from the carb to the intake manifold.