Ross Racing Pistons with engine bore sizes of 3.500" (90mm) and above can be machined for any popular ring combination at the time of manufacture.

All compression ring grooves at ROSS are machined to the Society of Automotive Engineers (SAE) D-Wall specifications (except dykes rings which have a radial thickness of .170"), unless the customer requests otherwise, or ROSS supplies the rings.

The radial thickness can easily be determined by using the following formula:

• Radial Thickness = Bore Diameter divided by 22
• For example: 4.250" bored divided by 22 = .193"
• The radial thickness of a 4.250" bore D-Wall ring is .193"

 

This is the standard depth used by leading ring manufacturers such as Childs and Albert, Speed-Pro, and Total Seal. ROSS STRONGLY recommends that you have us supply the rings for all custom pistons that are manufactured for a bore size of 3.500" (89mm) or smaller. If you insist on supplying the rings, you must give us the ring width and radial thickness on all three rings. In lieu of this information we can not accept “stock” or ring manufacturers part number.

Ring Side: (or lateral) clearance is the measurement of the space between the sides of the piston
groove and the ring.

Unless otherwise ordered, Ross will machine all pistons for a side clearance of .002" to .004". Some engine builders prefer to have us reduce the side clearance (especially with gas ported pistons), however under no circumstances do we recommend less than .001".

Ring Back Clearance: 

can best be measured by pushing the ring into the piston ring groove until it bottoms against the root of the groove.

The amount that the face of the ring is below the ring lands is the ring back clearance. It should not protrude beyond the lands when the ring is bottomed in the groove. All Ross compression ring grooves are machined for approximately .004 back clearance unless otherwise ordered. Ross will machine special groove widths or depths at no additional cost.

On all Ross Custom made pistons, you may specify the amount of spacing between the ring grooves.

In most instances, moving the rings up higher (thin lands) on the pistons will allow the pistons to be lighter, as the side mill cut can then be wider. Care must be taken not to make the ring lands too narrow (especially the top land) as detonation or high cylinder pressure can break thin lands. We feel that in most instances the customer should “trust our judgment” about the ring spacing.