Thread - Pilot Drill Charts

[Tony Smith]

Originally Posted by Jacques Reed

Good Day All,

Just a slight diversion from topic but which many may find interesting.

After posting a picture of my numbered drill set I remembered that Ford carburetor jet sizes are given in number drill sizes.

Cheers,

Not quite. The Holley Jet sizes closely correlate to thousandths of an inch; as the numbers go up, the Jets get bigger. Numbered drill sizes are related to wire gauges, as the numbers go up, the Drills get smaller. It was just a happy coincidence that your Number 54 drill fit a #54 Jet, as that is the point the two tables cross over.

BTW, never resize a jet with a drill bit. You will never get an accurate hole in the size you want. The WW2 Flathead Holley carburettors used jets and power valves that were standardised and are still used today in the latest Holley Quad Bore carbies. You can usually find a kit with a variety of different jet sizes to play with for a few dollars in most Auto Parts stores.