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Checklist for Fitting PML Small Block Valve Covers

PML valve covers looking good

Small Block Chevy Engines, Perimeter Mount, 1959 to 1986 Heads

We want to make sure you get valve covers that will work on your engine and you love looking at. With that in mind we have put together this checklist.

Disclaimer — Read This:

When building an engine, it's common for pieces not to fit together nicely. Thicker gaskets, some grinding, modification, tweaking and finagling may be needed.

PML does not recommend any of the modifications below. We are sharing suggestions from other customers. What works for one configuration may not work for yours. If these topics are not something you are comfortable with, talk with an engine builder.

Before You Buy Checklist

1.  Review PML Return Policy and Warranty

PML charges a 20% restocking fee and returned parts must be in new condition and returned within 30 days. Modifying a PML part voids the warranty. So check and double check. See our Returns Policy and Warranty.

2.  Understand How PML Checks Each Cover

At PML, we fit each valve cover we make on a GM cylinder head with standard stamped steel rocker arms.

We verify the flatness of the gasket flange surface is within tolerance (+/- 0.020 inch) and visually check for any defects.

3.  Select the Finish for the PML Valve Covers

All PML parts are sand cast aluminum. Sand cast aluminum parts have the texture of sand. Because of the sand casting process, no two parts are identical. We hand pick each set to give the customer a matched pair.

PML valve covers do not feel or look the same as chrome, stamped steel or die cast aluminum parts. Original 1960s Corvette valve covers are die castings, not sand castings, have a different look and feel.

PML valve covers come in four different finishes:
as cast, orange powder coated, black powder coated, and polished
        

The as-cast finish is the natural aluminum sand cast part. It will be a dull silver-grey and the texture will be rough like sand.

Powder coating is very durable and is baked on to the cover. On a powder coated part, you will see and feel some sand-like texture. It is similar to an orange peel. For a custom color or to match a color, purchase the as-cast finish part and work with a powder coater near you.

Our polish finish parts are not polished between the fins and the script. Polished sand cast aluminum parts show the normal characteristics of a casting. Polished sand cast aluminum valve covers will have some imperfections.

Read more about PML Construction and Finishes.

PCV hole on intake manifold side of PML Valve Cover

4.  Breather, PCV, and Oil Fill Holes

PML small block Chevy engine valve covers can be machined for PCV, oil fill, and breather holes without messing up the script and fins!

About half of our customers require PCV, breather and oil fill holes on the valve covers. Machining holes is an option and an additional cost.

See the pictures and read about the PML design for in this PDF about Oil Fill, Breather, and PCV with PML Valve Covers.

5.  Verify Clearance in the Engine Compartment for Larger Valve Covers

PML valve covers are about 3.3 inches tall from the flange surface to the top of the script or fins. See complete dimensions.

6.  Check Roller Rocker Height

Does the engine have roller rockers? If so, are PML valve covers tall enough on the inside? From the gasket surface to the inside top, PML valve covers have about 2.75 inches. See dimensions.

7.  If There Are Roller Rockers, Measure Space Between the Pins

PML valve covers have a baffle on the inside. When the covers are installed, the baffle sits between roller rockers. Plese read our web page on: Fitting PML Valve Covers and Roller Rockers

For roller rockers with large pins, PML can machine the baffle for additional clearance. These images show:

  • Measuring the distance between the pins
  • Baffle area unmachined
  • Baffle area machined to add more clearance for the trunion pins


measuring space between pins    baffle unmodified    baffle modified
Both sides of the baffle are machined. Click on image to view larger.

8.  Understand That Oversized Springs Can Contact PML Cover

An oversized spring may contact the baffle or the inside of the cover. A little grinding may be needed. This customer had Edelbrock 77760 wide body rockers with a 1.5:1 ratio. PML machined clearance for the pins. The customer found that the springs also contacted the baffle and using a dremel tool removed a bit more material.
baffle modifications

9.  Identify the Cylinder Heads

PML fits each valve cover on a standard GM cylinder heads. Aftermarket heads can have a slightly different rail so the valve covers may not fit the same. PML covers have thick walls so are slightly wider than stock covers. The gasket rail is also larger. Sometimes removing part of the gasket rail or using double thick gaskets can help fit PML covers on aftermarket heads.

Picture shows the modification from a customer with Brodix heads. He found that the edge of the valve cover hit on the heads. By machining the bottom edge (not the intake manifold edge) of the valve covers, he made the gasket rail thinner and got a good fit. Click on image to view larger.

After modification, PML valve covers cannot be returned so make sure this is something you are comfortable with.

10.  Look at Intake Manifold

Depending on the configuration, an aftermarket intake manifold may prevent PML valve covers from seating completely on the heads. The intake side may have a ledge or extra casting material that contacts the larger PML cover at the bottom. A little grinding or a double thick gasket can help.

11.  Stud Girdles Will Not Work

PML small block Chevy engine valve covers will not work with stud girdles. Be sure you do not have stud girdles.

12.  Gasket

PML recommends a cork or cork composite gasket. We sell some for $20.00 (set of 2). Our gasket is about 0.180 inches thick. This is a picture of our gasket on our valve covers.
PML gasket for small block Chevy valve covers

We do NOT recommend thick rubbery gaskets or any gasket that is molded with a metal insert.

If you decide to use double thick gaskets, you might need longer bolts.

You completed the checklist! Congrats! Contact us if you have additional questions. We have a loaner program if you need a cover to test fit.

General Motors Trademarks are used under license to PML, Inc.