1-5/8 Inch Fill Cap with Aluminum Bung

1-1/4-12 Straight Thread
Cap Weight: 1.06 oz.
1-1/2 in. Outside Diameter Bung
1/2 in., 1 in., or 2 in. Bung Height
(Cap Replacement O-Ring is C73-749)

2 Inch Fill Cap with Aluminum Bung

1-1/2-12 Straight Thread
Cap Weight: 1.62 oz.
2 in. Outside Diameter Bung
1/2 in., 1 in., or 2 in. Bung Height
(Cap Replacement O-Ring is C73-769)

2-3/4 Inch Fill Cap with Aluminum Bung

2-1/4-10 Straight Thread
Cap Weight: 3.32 oz.
2-3/4 in. Outside Diameter Bung
5/8 in. Bung Height
(Cap Replacement O-Ring is C73-788-A)

4-1/4 Inch Fill Cap with Aluminum Bung

3-3/4-8 Straight Thread
Cap Weight: 7.86 oz.
4-3/8 in. Outside Diameter Bung
7/8 in. Bung Height
(Cap Replacement O-Ring is C74-788-A)

The lightweight, non-vented cap features positive grip finger notches that are easy to get a hold of. Prime 6061-T6 billet aluminum is precision CNC machined into a lightweight, attractively designed cap; featuring quick-start coarse threads. Each screw on Cap is fitted with a Buna O-ring; positive sealing and "radially squeezed" to hold the cap secure.

Perfect for Custom Tank Fabrication

Get a Step Ahead

Your fabricator will appreciate the stepped shoulder at the base of the bung, it serves as a positioning locator. This feature holds the bung in place while welding in a hole of a flat surface, or in the end of tubing when constructing a filler neck extension. This grouping of cap assemblies includes a weld-able bung. 

Note: Welding should always be performed by a qualified welder.

Great Caps - Great Colors

To compliment the color coordination of your project, the caps are finished off in Pro-Werks Brilliance anodized colors in your choice of Black, Red, Blue, or beautifully Micro-Polished aluminum – the finishes are impeccable!

The Right Size Matters

Easy Turn Fill Caps come in many sizes and are packaged as complete assemblies with your choice of one of the many versatile mounting options, or each component is also available separately.

Proudly Made in the USA

Be sure to check out the entire line up - Billet aluminum Easy Turn Fill Caps are a Pro-werks specialty.

You can always count on Pro-Werks to do it right!

Customer Comments:

"I use your bolt on caps and bungs on my carbon fiber Cummins common rail valve covers. Love the quality. Thank you."
– Randy Davis, Owner of OldSkoolFab, Inc.

"I upgraded my fuel cell to an Easy Turn fill cap assembly. It wasn't long until all my friends did the same. Great product!"
– As shared with us at the PRI Show

Frequently Asked Questions:

Q: How much do I need to tighten a fill cap?
A: It is not necessary to bottom the fill cap into the bung−just adequately seat the O-ring. The radial squeeze action on the O-ring creates a positive seal and helps prevent the cap from coming loose.

Q: What should I use to lubricate the Buna O-ring?
A: Applied periodically, a light coating of Dielectric grease has proven to work well as an O-ring lubricant.

Q: Is Buna rubber compatible with my fluid?
A: Buna is a synthetic rubber compound suitable for use with many fluids. Buna components may need to be replaced by a material compatible with the specific chemistry of some fluids.

Q: How do I properly weld my bung?
A: Apply several small, equally spaced tacks and preheat before welding. Keep the weld small to minimize potential distortion or shrinkage.

Q: If my threads are tight after welding, how do I fix it?
A: The solution is simple. Apply a small amount of fine grit lapping compound to the threads then turn the cap back and forth in the bung until the desired fit is achieved. Be patient−do not force the process. Thoroughly clean both sets of threads before use.

PRO FABRICATION TIP: How to Calculate Tank Capacity

You can calculate how many gallons of fluid a tank will hold by dividing the total cubic inch volume by 231. As an example a basic rectangular shaped tank measuring 12"(L) x 12"(W) x 10"(H) = 1440 cubic inches. The next step is to divide the total volume of 1440 cubic inches by 231 = 6.23 gallons.

If your tank is an irregular shape, or has unique features, calculate the cubic inch volume of those areas also, then add or subtract the values to arrive at the total cubic inch volume of your custom fabricated tank.