Choke Horn Removal - Applicable To SC520pr and SC520pb STREETCATCHER
Choke Horn Considerations
The SC520Streetcatcher is designed to mount directly to Holley, Holley Avenger and Holley HP, QFT (Quick Fuel Technology), AED, ProForm Inline and Sideways Squarebore Dual Carburetor setups and the popular Edelbrock Performer 1400 series and AFB Carter Comp series and pretty much all Demon Carburetors.


The SC520Streetcatcher adapters will clear the choke horns on the Edelbrock Performer and Carter AFB Comp Series carburetors, however, you will need to remove the choke plate and operating linkages.

If you are looking for maximum airflow it will always be beneficial to remove the choke horns completely.

Basic Choke Horn Removal
If you are using carburetors with a choke horns in-line or sideways you will need to remove the choke horns. Many performance Holley's, Demons and QFT's come with no choke horn direct from the factory

Remember don't remove the center threaded boss in the center of the four barrels, the adapters are designed to accommodate these or the thread boss can be lower in the case of carbs that come with no choke horn from the factory, leave them as they are so you don't need to drill deeper or re thread them.

All you need to do is remove the 'choke horn' housing away from each side of the center boss and vent tubes by cutting carefully with a hacksaw, and clean them up with a file or die grinder.

Sideways Mount Setups will fit with no vent modification

Cut the bowl vents (some are integrally cast or some have steel inserted tubes sticking up between the venturi's at the front and the back of each carb just inside the 5 1/8" neck diameter). Cut them to an overall height of 7/8" and angle the top about 45 degrees with the tallest part of the angle toward the center of the carb and the lowest part of the angle toward the bowls.

You will need to remove the front and rear bowls and put rag in the top of the carbs to stop filings going down into the air bleeds etc.

If you are not confident to do this , any performance carburetor or competent machine shop, could do this for you. It is a common and relatively small job, but if you do have a carb shop do this ask them to mill the center divider section of the choke horn (between the front and rear barrels) right down to the top of the venturi's, this would certainly help air flow.

The SC520Streetcatcher will fit Mighty and Race Demons which come with no choke horn from the factory, and could be fitted to Street Demons with the choke horn removed (re Holley Info above). The only other modification is that the Demons use a 5/16" diameter center stud, which would require simply drilling out the adapter center hole to 5/16": clearance and changing the allthread studs from 1/4" to 5/16". Also on the Street Demons there may have to be slight modifications to the rear adapter for bowl vent clearance.

QUICK FUEL TECHNOLOGY (QFT) CARBURETORSThe Quick Fuel Technology Carburetors are the same as holleys other than they have a 5/16" center stud as does a Demon.

The SC520Streetcatcher would fit PREDATORS but would need a 5/8" high 5 1/8" carb neck spacer under each base adapter to lift the base adapters up this amount for clearance because the predators have a steel tube hoop across the top of the carb that sits higher than a holley and it holds the 1/4" stud used to hold the air cleaner or scoop adapters down.