Setting Ring Gaps:One of the most frequently asked question we get is: How do you install rings properly? So here goes.
Top Rings :
Molybdenum faced, barrel lapped, ductile spheroidal graphite iron. Phosphate coated, or gas nitrite steel barrel faced.
Second Rings :
Grey cast iron, reverse torsional twist, taper faced, zinc phosphate coated, or Napier.
Oil Rings :Stainless expander, circumferential type, Chromium plated rails, low redial depth.
END GAP
ROSS RACING RINGS for the top and second groove are oversized and must be fitted to obtain proper end gap. The proper amount of end gap required is directly dependent upon the amount of heat to which the top ring is subjected. For normally aspirated engines. The end gap on the ring in most cases should be bore size in inches X .004,(to convert mm to inch multiply the bore size in mm X .03937).
To determine the proper end gap on the second ring on normally aspirated engines multiply the bore size in inches X.005. It is recommended that the Second ring have more end gap than the top rings to allow any blow-by gasses passing the top rings to quickly escape to the crankcase. If the second ring gaps are set smaller than the top ring gaps, the engine may show less leak down under static conditions but at high speed pressure may build up under the top ring and lift it, causing flutter.
Engines don’t run under static conditions! Should top ring land be .180 or narrower add .002 total to the above computed end gaps. EXAMPLE 3.625 (92mm) bore with..150 width top land: 3.625 X .004= .015 plus .002 for turbocharger-.019 total end gap.
For engines that are blown, turocharged or run nitrous ststems of more the 30 horsepower per cylinder add .004 total to the end gaps shown above.Example 3.625 X .004=0.15 plus .004 for turbocharger-.019 total end gap.
CYLINDER HONING
When boring the cylinders, allow a minimum of .003 for finish hone. (If finish bore size is to be 3.500, bore to dia. of 3.497) Any less than this will leave boring marks remaining after honing and will prevent proper ring seating.
USE TORUE PLATES WHILE HONING OR THE PISTONS WILL PROBABLY SCUFF AND THE RINGS WILL NOT SEAL…
Two stages of honing are required to achieve the fine surface finish which we recommend for Ross Racing Rings. The first stage is used to bring the bore to a size .0005 smaller then the finished bore size.
Honing speed should be approximately bore diameter in inches divided into 1000 (ie for 3” bores 3000 RPM and for 4” bores 250 RPM) We recommend a 30’ cross hatch included angle. First stage honing be grit. Use care to avoid burnishing or burning cylinders.
Install the oil rings first. Wind on the stainless expander first with the ends pointing down and butting.
Next install the upper rail before installing the bottom rail. If attempting to install the lower rail first the assembly will become tangled as the rail passes over the expander gap. Install the upper rail gap about 90’ counterclockwise from the expander gap. Install the lower rail with the gap about 90’ clockwise The reason that the rail gaps must be separate from each other and the expander gap is to avoid overstressing of the expander. If the two rails are fitted with their gaps in line the friction effect of the rail inners against the expander rail support pads will cause most of the relative movement to be concentrated over a small number of humps. This will cause the most highly stressed hump to break. Also, the expander will either overlap or become tangled if its gap is assembled inline with either or both of the rail gaps.
Next install the second ring with the dot to the top of the piston, if the set includes a second ring which has an internal chamfer. If the second ring has a, Napier groove or “hook” on one of the surfaces that contacts one the ring groove sills, install the Napier groove “hook” facing the bottom of the engine. Install top ring last. If the there is a dot on the top ring, install with the dot to the top of the piston. If there is no dot on the top of the ring, but there is a chamfer on the inside diameter, install the chamfer to the top of the piston. If there is no dot or chamfer on the ring, it is a symmetrical and can be installed in the groove either way.
Spin all rings in groove to be sure that the rings are free in the grooves. Check ring side clearance with a feeler gages. The top compression rings and second rings should have a side clearance of .002 to .004 unless the pistons are gas ported- With gas ports it is permissible to run the side clearance as tight as .0015. Ross racing Oil Rings should have between .003 and .005 side clearance.
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 rings 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. Ross Racing Top and Second Rings should have approx. .004 back clearance. To allow oil (which has been scraped off the cylinder wall by the top oil ring rail) to flow radially to the oil return holes, we recommend approximately .030 back clearances with our oil rings.
Please note that all three mm or narrower oil rings, regardless of the brand, work best with split radius oil return holes in the pistons. ALL ROSS RACING PISTONS include split radius oil return holes with three mm or narrower oil ring grooves.
End gaps on the top two rings should be staggered approximately 180’ Lubricate pistons and rings with a premium grade oil of at least 20w/50 weight before installing in the bores .Low viscosity monograde oil is not recommended. Do not use additives, either for initial lubrication or in the engine oil system, until the rings have seated.
El Segundo, CA 90245
www.rosspistons.com
ORDER LINE(800) 392-ROSS (7677)
TECH LINE (310) 536-0100
FAX (310)536-0333
