Many Holley or Demon Double pumpers come with no choke horn as supplied from the factory however most universal type double pumper carburetors are available with chokes.

If your carburetor has a choke it needs to be removed for use with SC500 style enclosed carb STREETCATCHERS

This applies to double pumpers being used in the SC500 6/8-71 Blower Scoop also in the SC500-177 used on the Holley/Weiand 142/144/174/177 series PowerCharger and Pro-Street superchargers and also the Holley/Weiand 250/256 mid sized blowers.

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.

Cut the bowl vents
HOLLEYS: (some are integrally cast or some have steel inserted tubes sticking up between the venturi's at the front and the back just inside the 5 1/8" neck diameter).

The front Vent is OK if it is not over 1 3/4" high as measured from the carb neck surface (where an air cleaner would normally sit on) and the rear vent needs to be kept no taller than around 1 1/4' When you cut the vents make sure you 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.

DEMONS: On Demons all you need to do is lower the rear vent about 1/4"

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

The Demon bowl outlets are slightly different to the Holley. The Demon bowl outlets are slightly wider apart and slightly lower than the Holleys hence the SC500 adapter needs a little more clearancing for fuel line entry when a demon carb is used, also the Demon bowls use the 9/16-24 thread and the Holleys use the 7/8-20 thread.

There are a number of ways you can set up your fuel lines, you can use the standard Chrome dual feeder fuel lines that are used on normal double pumpers or you can use the custom style red and blue Earls XRP Russell style anodized fittings.

You‚ll notice on the top picture of the Holley carburetor the rear fuel line bowl entry is right up close to the bowl and the fuel line is routed up over and then down past the rear pumper arm setup. This hides the fuel lines up inside the scoop more if you want it that way.

Earls make this fitting (Pt no 849094 for Demon carbs 9/16-24 thread) and (Pt No 849093 for Holley carbs 7/8-20 thread)

If you want to run individual straight extensions out of your bowls as in the top Demon picture they are XRP part No