Functional Air Cleaner for Goodmark Cowl Hood

Posted By: Z65_Paul

Functional Air Cleaner for Goodmark Cowl Hood - 10/10/07 05:30 AM

This article describes a custom made air cleaner assembly using, of all things, a round cake pan as the foundation to adapt an open element air filter to the circular opening on the Goodmark Steel Cowl Hood. While not the first to come up with the idea of using a cake pan for this application on the internet, this article is the most detailed write-up you will find on the subject, and the first application known to date on a Monte Carlo SS.

This project is written for, and the pictures depict a 4th Generation (1983-1988) Monte Carlo SS. Before ordering any parts, be sure to take geometry measurements within your engine bay to make sure the 18x3" pan, plus a 3/4" raised air cleaner base will fit! Don't assume they will because you have the same car. Engine bays can have differing geometry even between similar cars. As long as proper adjustments are made for differing geometry, the idea can be adapted to other applications very easily.

Here are the parts used in this project, along with links.


  • The first step should always be baseline measurements of the engine bay.

    • Take note of the alignment between the center point of the carburetor and the center of the Goodmark Hood hole opening. On the 4th Generation Monte Carlo, the engine sits approximately 1 inch closer to the passenger side. This creates an offset between the air cleaner assembly and the hole if not taken into account. I chose to offset the assembly by 1 inch to compensate for this difference.
    • Next, take a measurement from the center point of the carb outward from 9 to 10 inches in all directions. Look for potential interference points. On the 4th Generation Monte Carlo SS, I found the closest interference point is the cruise control actuator on the driver's side of the distributor. In the final configuration, the foam will touch the edge of the actuator, but will not interfere with its operation.
    • Next, place the raised air cleaner base on the carb. Ensure there are no interferences with the carb linkages. Since it's a raised base, the likelihood of interference should be very low.

  • Once you've convinced yourself that all interferences have been accounted for, map out the hole to be cut on the bottom of the cake pan. Refrence: IMAGE #1

    • Start by finding the center point of the cake pan. If you order the same pan listed above, the center point is half way down the number "1" where it lists "18x3". Mark horizontal and vertical scribe lines on the bottom of the pan from this mark. I used a right-angle to ensure the lines were perpendicular to each other.
    • If you choose to offset the assembly to compensate for the difference between engine centerline and the Goodmark hood hole, mark a second center point on the bottom of the pan by that amount. In my case, I offset by 1 inch as shown in the picture.
    • Using a point compass, scribe an 11 inch diameter circle around the new center point. The 11 inch diameter matches the inside diameter of the flat portion of the air cleaner base (as shown in the picture). If your air cleaner lid is different, adjust appropriately.

  • Next, cut out the section of pan scribed by the circle. Reference: IMAGE #2

    • I used a dremel tool with cut-off wheel.
    • Be sure to debur and round the edges of the hole once cut.
    • Compare the cut hole with the air cleaner base footprint.

  • Time for a trial fit on the engine. Place the pan on the carb, followed by the air cleaner base. Adjust the pan and get a feel for the fitment, looking for surprise interferences. Remove from engine when done.
  • Next place the air filter into the air cleaner base. Take note of the amount of available space between the inside edge of the air filter and the outside edge of the non-flat area. This is where you'll drill holes to secure the lid to the pan. You should have approximately 1/2 inch to work with.
  • Mark and drill the air cleaner base.

    • You will be drilling 8 evenly spaced (45 degrees apart) holes. To get them evenly spaced, I started by placing two perpendicular strips of masking tape across the air cleaner base. Then followed up with two additional strips of masking tape at 45 degree angles to map the last 4 holes. You'll be able to easily see if your alignment is off. Look for similar angles between each successive strip of tape.
    • Next, mark and center-punch a spot (8 locations) half way across each tape, at approximately 1/4 inch away from the outter edge of the non-flat area on the air cleaner base.
    • Drill the 8 holes through the tape to match the size of screws you'll be using. Remove the tape when done. Debur the holes.
    • Do the holes have to be exactly 45 degrees apart? No. I'm just a perfectionist! Don't worry about it if they're off slightly. They will be out of view in the end product. Just make sure your screw heads are ultimately inside the inner diameter of the air filter.

  • Drill the cake pan.

    • Align the air cleaner base to the cake pan. Be sure to account for the clocking of the valve cover vent tube on the bottom of the air cleaner base. That tube will interfere with the linkages on both sides of the carb.
    • Recheck the alignment on the engine. Make alignment marks on the inside of the cake pan and the air cleaner base at the center rear so you can re-align them on the bench and center the foam later.
    • Secure the cake pan to the air cleaner base using masking tape. Make sure your alignment between the air cleaner base and cake pan is correct.
    • Match-drill (drill through the hole on the air cleaner base into the cake-pan) the first hole. Temporarilly secure this hole with a screw and nut.
    • Match-drill the second hole 180 degrees away from the first drilled hole. Temporarilly secure with a screw and nut.
    • Match-drill the remainder of the holes.
    • Remove the masking tape and two screws holding the two parts together. Debur all holes.

  • Secure the cake pan to the air cleaner base. Reference: IMAGE #3,
    IMAGE #4

    • Make sure the alignment marks on the pan and base are correct.
    • Secure with screws, nuts and split washers.
    • The seal between the air cleaner and cake pan is very good for this application. However, if you are more anal about things than I am, you could lay down a strip of silicone sealer between the pan and air cleaner base to provide a completely water tight seal.

  • Cut the fire retardant foam. Reference: IMAGE 5

    • Take a sharp knife and mark it with masking tape 2 inches from the tip to be used as a depth gauge.
    • Make a 2 inch deep cut down the center of the fire retardant foam (this is the initial cut).
    • Place the foam around the edge of the cake pan with the ends meeting at the back (at the point of your alignment mark). Cut off the excess (approximately 2 inches).
    • Place the air cleaner assembly on the carburetor, with the filter and lid. Secure the assembly to the carburetor with the wing-nut.
    • Slowly close the hood enough to see the alignment of the foam to the hood opening. Readjust (rotate) the air cleaner assembly as necessary to align the foam to the hood opening.
    • Close the hood more until initial contact is made between the hood and foam. Note the distance of the remaining hood opening. Re-open the hood and remove the foam from the air cleaner assembly.
    • Cut an additional depth (1/4 to max 1/2" as needed) into the initial foam cut. Incrementally increase the tape depth on the knife for a depth gauge for a controlled cut.
    • Reinstall the foam on the air cleaner assembly with the ends meeting in the back. Repeat the hood measurement.
    • Repeat this process in small increments (1/4" to 1/2" at a time) until a good seal is achieved between the foam and the closed hood. Remember, you may have to have a deeper cut at the back of the air cleaner (ends of the foam) than the front of the air cleaner (middle of the foam) for a full seal.
    • In my case, I ended up with a 3 inch deep cut around the entire foam.. making the foam bottom out in the pan. Reference: IMAGE 6, IMAGE 7. Don't assume yours will be the same. Use the small increment process to creep into the correct amount of cut.
    • Once you are happy with the foam to hood seal.. remove the air cleaner assembly from the engine.

  • Secure the foam to the cake pan.

    • Remove the foam and filter from the air cleaner assembly.
    • Add a piece of mounting (double-back) tape around the outer circumference of the pan, approximately 1 inch above the lowest point of the foam. Do not remove the outter tape backing yet. Reference: IMAGE 8 As an alternative, you can use spray adhesive or weatherstrip adhesive to secure the foam to the pan.
    • At the rear of the pan where your center rear alignment mark is located, attach additional mounting tape to help secure the ends of the foam. Do not remove the outter backing yet. Reference: IMAGE 9
    • Place the foam back on the air cleaner assembly with the ends meeting at the center rear alignment mark. Make sure the foam is properly aligned and completely seated on the pan.
    • Working slowly around the pan in small sections, remove the mounting tape outter backing and press the foam onto the outter sticky side of the tape. Do the same at the ends with the extra pieces of mounting tape.

  • Place the air cleaner assembly back on the car with the air filter and secure with a wing nut. Adjust alignment (rotation) if necessary. Reference: IMAGE 10
  • Close the hood slowly to ensure good seal between the foam and hood. You're done!

Other Views of Completed Assembly:

I hope you found these instructions easy to follow. They were written in excruciating detail exactly as I performed each task so nothing would be left out. If you have any questions, comments or improvments about this project, or if you create one of these for your own setup, please drop me an e-mail.

Good Luck!
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