Head Sealing
While “O” ring heads are a very popular technical fashion for many closed course racing platforms, sealing the large 89mm bore diameters of the 845 is a tall order for any head, much less an “O” ring head. We built the 845 kit to utilize an all metal head gasket in order to offer the widest possible sealing surface area around the bores. In addition, the sleeves of the 845 are manufactured with a very wide sealing rim on the top flange to further increase sealing area width. This arrangement allows the 845 to have a head sealing surface width that cannot be matched by any “O” ring type head setup.
Many owners understandably want a “girdle” type cylinder-head to help reduce the possibilities of fracturing the cylinder casting (as happens to numerous modified 61x cylinders). It bears noting that the 62T and 64X cylinder castings have additional casting supports, and are thicker in the areas where the 61X cylinders routinely fractured. Even with this extra casting mass, we felt that girdling support for the 845 was still in order. Since virtually all cylinder fracturing takes place on the inlet side of the cylinder, we opted to use a “Half-Girdle” that bolts on top of the head on the inlet side only. This half-girdle offers as much support as any “O” ring girdle head, and still allows the use of the stock 62T head casting. It bears noting that this girdle makes for very close clearance between the girdle plate and the flame arrestors of a dual 38 setup (dual 44s have plenty of clearance). To resolve this clearance issue, the dual 38s must be fitted with extended flame arrestor adaptors that raise the connection for the pods safely away from the girdle plate
