1966 Ford Bronco Air Filter Adapter

Purpose & Objective

A relative of mine owns an antique Ford Bronco. The 1966 model year utilized an “oil bath” air filter for the engine’s air intake. These filters are outdated, so I designed an adapter that allowed him to use a more modern K&N air filter. As of 2021, it is still undamaged and being used, five years after it was originally installed.

The completed air filter adapter, with the older oil-bath air filter in the front right of the image.

Design Choices

The original filter attached to the manifold with a singular threaded stud, visible in the image. The new K&N filter attaches only to a tubular boss, with a hose clamp to keep it attached. This meant that I’d need a portion of my model to extend into the manifold, but without blocking airflow. It would also need to seal against the sheet metal.

CAD model of the air filter adapter.
Experimenting with the FEA capabilities in Fusion360. The accuracy of the values were not as important to me as identifying potential problem locations.

I chose to use 3 radial webs to reach this central mounting point, as in the below pictures:

Test-fit of the print. I used ABS plastic for this print. Note the taper on the ID, and ribbed shape of the webs for strength and improved airflow.
A heated bolt was pressed into the center, permanently attaching it as a stud, so the design is easily swapped with the original air filter with no other modifications.

Installation of the Air Filter

The design has worked well, and I recently confirmed that it’s still without cracks or damage in 2021, nearly five years after it was originally installed.

The print passed the fitment test.
Very small grooves were printed to match the injection-molded ribs on the ID of the K&N filter.
Another view of the installed air filter adapter.