GM Storm/Spectrum 1985-1993 Repair Guide

Valve Seats



Due to the high degree of precision and special equipment required, valve seat replacement should be left to an automotive machine shop. Although the seat replacement procedures are virtually the same for all of the Spectrum and Storm engines, the specifications are unique to each cylinder head application. The following procedure can be construed as what is generally acceptable for aluminum cylinder heads; the actual method employed should be the decision of the machinist.

The Chevrolet and Geo engines use replaceable seat inserts. These inserts can be removed by cutting them out to within a few thousandths of their outside diameter and then collapsing the remainder. Another method sometimes used to remove seat inserts is to heat the head to a high temperature and drive the seat out.

Upon installation, the new seat may be installed with the cylinder head heated to a high temperature, then the seat, which is at room temperature or slightly chilled, is pressed into the head. The head is then allowed to cool and as it does, it contracts and grips the seat. In certain applications, the new seat may be driven in with both the head and seat at room temperature. The calculated press-fit interference will then retain the seat in the head.