Model B Power Jet Tube

Model A Ford Garage

Removal & Installation Instructions

The pic above shows the brand new exact replacement power tube I reproduce from stainless steel tubing. It is the correct ID and OD and length per the original Ford detail drawing researched at the Benson Ford Research Center.

I sell the power jet tubes on eBay as well as direct with payment through PayPal. They are not available through any catalogs or other outlets. Please contact me for more information or to order.

Contrary to conventional wisdom, this tube is not a standard size, and is not available from hobby stores, old ball point pen cartridges, etc. This is a special size tube and is reproduced to-print with the exception that is made from stainless steel whereas the original was brass. The stainless will not corrode, and is also stronger than the original fragile brass tube.

The pic above shows the installed tube which is 2-1/16 inches long. When the tube is pressed into the casting there should be 1-1/2 inches of tube beyond the gasket surface (1-9/16 max). The fit of the tube is a minor press fit into the casting. It is not a slip fit.


Tube Removal

You win a few and you lose a few! The early carb core on the left had every single tube in it broken off! The late carb core on the right was like NOS inside, in spite of it's grubby exterior appearance.

If the power jet tube is already broken off at the base like the carb on the left, one method to remove it is to drill it out with a number #43 drill, and then tap it with a 4-40 tap. Do not drill beyond the length of the tube remnant! Thread in a steel 4-40 screw and use that to get a handle on the tube remnant to pull out.

Do not use the tap as a puller or your next dilemma will be trying to remove a broken tap from the hole! Drilling the tube progressively larger may also work, though you must not go through the brass. Do not use a drill diameter larger than about a number #38.

If the tube is not broken, you can use a pop rivet tool with a 1/8 inch nose to pull the old tube out of the casting. The tube is smaller than 1/8 inch OD, but I have found that the pop rivet tool collet can still work.

Another method if you need to remove the old tube or a portion of it, is to insert a number #45 drill blank into the tube and then clamp onto the tube with a pair of vice-grips and carefully pull the tube straight out.

You can also use the slide hammer attachments which attach to vice grips. Do not rock the tube back and forth or you will break it off at the base in the casting.

When the old tube is pulled out for replacement, it is important to also make sure that the air bleed (vent) hole in the casting at the top of the tube is not obstructed. If the vent hole is plugged, the gas well will be air-locked, and the power tube will not be able to function properly.

A #60 number drill bit is the air bleed hole size, as shown above with a drill blank inserted in the vent hole.


Tube Installation

The method I use is to grip the tube in a collet with exactly 9/16 inch of tube length protruding beyond the collet face (2-1/16 minus 1-1/2 equals 9/16 inches). I then use an arbor press to press the casting onto the tube in the collet holder. When the collet contacts the gasket surface, the tube is at the proper position.

This is the collet holder and an R8 collet for gripping the tube during installation into the casting. When pressing the tube into the casting, it is important to support the tube against buckling or collapse, and also to press exactly perpendicular to the casting.

Another method is to take a block of aluminum, steel, hardwood, or even a long bolt and drill a deep number #33 drill diameter hole through the length of it. Then cross-drill a larger hole through the first, so that you can insert a stop pin across the number #33 hole.

Position the stop pin hole so that 9/16 inch of tube extends beyond the supporting structure. This will now support the tube against buckling and provide a tool for pressing the tube into the casting, as well as controlling the correct press-in fit dimension to the casting.


More related information on Ford Garage:

  1. Model A & B Zenith Carburetor Jet Sizes & Flow Rates
  2. Model B & 46 Zenith Carburetor Parts Catalog Illustrations
  3. Model B & 46 Zenith Carburetor Assembly Drawings
  4. Model B & 46 Zenith Carburetor Float Details
  5. Model B & 46 Zenith Float Valve Orifice Details
  6. Model B & 46 Zenith Carburetor Power Jet Circuit
  7. Model B & 46 Zenith Carburetor Power Jet Tube
  8. Model B & 46 Zenith Carburetor Catalog Data
  9. Model B & 46 NOS Zenith Carburetor
  10. Model B & 46 Zenith Carburetor Upper Casting Variations
  11. For more Model A & B Zenith carburetor web pages, use the Site Search box at the top or bottom of this web page.

February 2004