These series engines use cylinder wall technology that is a development of the process pioneered by GM/Reynolds for the Vega. The monoblock is cast from a high silicon aluminum alloy, and the cylinder walls are etched after final honing to remove surface aluminum, whilch creates a very hard silicon wear surface. Pistons skirts require an iron plating and three thin platings of other metals are required between the aluminum skirt and final iron film in order to achieve proper plating adhesion.
For field repair, the cylinder can be bored and honed, then subjected to a "silicon lap" to remove surface aluminum, which yields the same result as the original chemical etching process.
Other alternatives are iron or high silicon aluminum alloy liners that can be installed after the cylinder is overbored to accept the liner. If the final bore surface is the properly processed aluminum silicon alloy, a properly plated piston should be used. Iron liners only require a conventional aluminum piston without the skirt plating.
When I recently refreshed the cylinder head on my Cosworth Vega (very worn valve guides) I noticed some minor scoring on one cylinder's major thrust surface. The engine made excellent power before the work and I attributed the high oil consumption (about a quart every 300 miles) to the worn guides and poor OE seals. I decided to complete the head refresh (new guides and a new design seals) and install it without rebuilding the block. Oil consumption dropped to nearly unmeasurable, and all the power is still there.
These aluminum-silicon bore engines have some tolerance for scoring, but without seeing it, it's tough to make a judgement.
Last edited by Duke2.6; 12-09-2003 at 10:50 AM.