Electric Fuel Pumps...

[Ralph A Powell]

As I remember the diameter of the fuel passage in the old blue Holley regulator is only .224. When I was doing some development work on the first annular 4500 hundreds the Holley engineers told us that the cross over for a second regulator was 580hp. The old blues were very smooth operating regulator’s.

[Adger Smith]

Originally Posted by Ralph A Powell

As I remember the diameter of the fuel passage in the old blue Holley regulator is only .224. When I was doing some development work on the first annular 4500 hundreds the Holley engineers told us that the cross over for a second regulator was 580hp. The old blues were very smooth operating regulator’s.

If my memory serves me correctly that is about right on the hole size, but it has a pin that is off the diaphragm to push the ball open. That pin is about .090 in diameter and reduces the area of the .224 opening. On my 2X4 modified cars I drilled out the metal sleeve and installed a larger diameter one for more flow to keep the float levels up.