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Finishes and Construction

We believe in producing the highest quality part possible. PML pans and covers come in several finishes to accommodate a variety of requirements and aesthetics.

All our parts are sand castings. This means they have the texture of sand and no two sand cast parts are completely identical. Even after powder coating or polishing, there is still some texture and imperfections.


PML offers parts in:

  • Polish Finish
  • Powder Coat Finish
  • Natural As Cast Finish

The only difference between the finishes is how the part looks, no difference in function.

No two parts are completely identical. The sand casting process makes each one unique. If you order valve covers, we hand pick the covers to give you a matched set.

Polish Finish

For the polish finish, the natural cast parts are hand polished.

Our polish finish parts are frequently used on show trucks and cars but our polish finish is not fully show polished. For example, the area between the fins is not polished and bolt hole areas and small corners are not detailed. By leaving the areas between the fins unpolished, we believe the fins and script stand out and we are able to produce a beautiful polished piece at a reasonable price.

If you need a fully show polished piece, you can purchase the polish part and go from there or purchase the as cast part and have it polished to your specifications.

Polish parts always have minor imperfections, inherent in the sand casting process.

Sand cast aluminum parts have a rough surface, like the texture of sand. When sand cast aluminum parts are polished, it is not uncommon for some porosity (very small holes) to be uncovered. This is normal and inherent in the manufacturing process. To our customers this is a sign that these parts are unique and produced in small quantities.

Polished sand cast aluminum valve cover Close up of polished valve cover
This is a close up of a polished finish valve cover. Note that the area between the fins and script is not polished. When close up, some tiny dots of porosity are visible going down the side of the cover.

The polish finish requires careful handling and maintenance. For that reason, most polish finish parts are found on show vehicles or on restored classics, not on work trucks or daily drivers.

The polish finish is NOT chrome. Chromed parts are shiny all over and look different than polished sand cast aluminum parts. A chrome finish is also easier to maintain than a polished aluminum part.

Examples of polish finish parts. Click on an image to view a larger one.

Polished lettering and fins Polished valve cover lettering and fins. Area between not polished.   Dots or porosity Polished valve cover, small dots of porosity on edge and side of cover.
First Image: Area between fins and script not polished.
Second Image: Small dots of porosity on side of cover.

End of a polished part End of polished valve cover with bolt hole, area between fins not polished, small dots of porosity.   Bolt hole area of polished valve cover Marks on bolt hole area of polish valve cover.
First Image: Bolt hole area not polished and some porosity visible on end. Area between fins not polished.
Second Image: Bolt hole area polishing marks and not fully polished.

Powder Coat Finishes

PML's powder coated parts have the finish baked on to our sand castings. Powder coating is a very durable finish. Powder coating looks like paint but it is tough. After powder coating, we brush off the top of the fins and script to remove the powder coating and the aluminum shines. This gives a nice, classic look.

Powder coated parts are the easiest to keep clean.

On our valve covers, we use glossy smooth powder coats. The resulting texture is similar to that of an orange peel. We offer black powder coat on all valve covers and on some we also offer red, orange, and blue.

On our differential covers and transmission pans, we use a black semi-gloss texture powder coat.

If you want a custom color, we recommend you purchase an as-cast part and have it powder coated locally to you. We have had people powder coat our parts in all colors of the rainbow. Some folks customize their vehicle by using high temperature spray paint on the cover or pan. Paint is not as durable however.

There is some debate that powder coating increases or decreases amount of heat that a part can dissipate but we do not know of any scientific studies.

Natural As-Cast Finish

This is the basic finish and all our parts start out like this. The natural cast finish is a dull silvery-gray color. There is some slight variation in the pigmentation of the metal so the pictured cast finish part may not exactly match the one you receive. The pigmentation may darken over time.

Sand cast aluminum parts have a rough texture, like that of sand. This surface finish is rougher than die cast, billet aluminum or stamped parts. This rough finish provides more surface area to help with heat dissipation.

PML parts will not rust as they are aluminum. Generally, PML differential covers and transmission pans are chemically sealed to resist corrosion.

Folks who want a custom color purchase the cast finish and then powder coat or paint their cover or pan themselves or at a local shop.

The cast finish can be difficult to keep clean because of the light color and rough texture. Scrubbing with Simple Green or soap and water can help clean it up.

If a sand cast aluminum part is chromed, it will be shiny but still have the bumpy texture of sand.


PML uses high grade aircraft quality aluminum and makes parts using the sand casting process. This is the same processes that are used to make intake manifolds, water pumps, and engine blocks. Sand cast parts have the texture of sand. PML covers and pans are manufactured in Southern California in small batches, not in huge quantities offshore.

The design and construction provides strength. The walls and the gasket flanges are thick. PML parts will not bend or flex. The result is added strength to the transmission case or differential housing and gasket flanges that provide a secure seal.

Aluminum material promotes heat dissipation. This aids in cooling transmission and differential fluid to keep the fluid lubricating gears and seals.