Q: Why do I need a DuraShim Cylinder Head Spacer Shim?

A:  Most engines today have aluminum cylinder heads. Compared to the cast iron cylinder head of yesterday, aluminum is lighter but less durable. As an aluminum cylinder head overheats, it is likely to warp. This can lead to a head gasket failure and many other problems.
  A perfectly flat surface is required for a head gasket to properly seal, so the warped cylinder head needs to be resurfaced. After resurfacing, the engine may run poorly because the thickness of the cylinder head is out of specifications. A DuraShim will return the cylinder head to the proper height.

Q: Are there other kinds of problems I will see on the cylinder head?

A:  Yes. Many times the fire ring in the head gasket will leave a deep impression in the cylinder head surface. To achieve a proper seal at the cylinder, a flat surface is required.
  Another potential problem is metal erosion caused by a blown head gasket. If the head gasket leaks, the coolant can actually erode and pit the surface of the aluminum cylinder head.

Q: What exactly does the DuraShim Cylinder Head Spacer Shim do?

A:  DuraShim Cylinder Head Spacer Shim restores the valve train geometry, valve clearance, compression ratio, and cam timing to factory specifications on engines where the cylinder head and/or block surfaces have been resurfaced.

Q: What would happen if I didn't use a DuraShim?

A:  If you use a cylinder head that is machined below specification, you may run into one or more of these problems: 1) The smaller combustion chamber causes higher compression resulting in engine knock. 2) Pre-ignition is caused by cam timing being out of specification. 3) Valves may actually collide with pistons during operation. 4) Pistons may make contact with cylinder head.

Q: How are DuraShims manufactured?

A:  DuraShims from Innovative Machine & Supply are precision cut from 0.020" cold rolled steel. Shims are individually produced using a CNC laser.

Q: What is the advantage to a laser cutter versus a punch press?

A:  DuraShims have clean, straight edges with no distortion to the flatness of the shim. A punch press causes a rolled edge and can curl the shim.

Q: What is the advantage of a steel shim over a copper one?

A:  DuraShims from Innovative Machine & Supply are made from steel for several important reasons:
  1) Steel has a higher heat tolerance than copper. In hotter running late model engines, heat resistance is very important to insure the integrity of the shim. Steel is superior to copper for this environment.
  2) Steel cylinder head shims have a hardness factor similar to that of the block. This allows the gasket fire ring to properly "crush" as the head is torqued to spec.
  3) Steel shims are less likely to be damaged in shipping and from mishaps in the shop.

Q: If the cylinder head is warped or damaged, shouldn't we use a new cylinder head instead?

A:  There is no good reason to scrap the warped or damaged cylinder head. Many cylinder head cores are in extremely short supply in the aftermarket. If you are lucky enough to find a replacement core, the cost will be much more than the price of a DuraShim. Obviously, the price of a new casting would be even higher. This makes the economics of the DuraShim very attractive.

Q: Do DuraShims ever fail?

A:  When used properly and with proper preparation, DuraShims are 100% reliable. DuraShims are used by many of the largest engine remanufacturers in the world.

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