The material commonly used is specified as 'Manganese Bronze' and very little other detail is provided.
The family of Manganese Bronzes covers a wide range of characteristics.
In terms of coefficient of friction, strength, wear resistance and thermal conductivity the most suitable of the Manganse Bronzes clearly work and they are quite easy to machine but the last few years has seem some very good advances being made in terms of performance.
Modern CNC machining and the use of tipped carbide tools has allowed other alloys to be used and some of these have much better properties and allow a 'better' guide to be manufactured.
Columbia Metals make a wide range of Bronzes and the material that they recommend is sold under the Colsibro brand name.
This material is a precipitation hardening Copper/Nickel/Silicon ally that has excellent strength, resistance to galling, low coefficient of friction and a Thermal Conductivity that is much higher than any of the Manganese Bronzes.
it is a material of choice for many F1 and LeMans engines and is used by companies such as GS Valves for all of the guides they sell in their Race Engine Components catalogue.
We have made 911 guides using Colsibro to a industry leading standard. All basic dimensions are within the tolerances shown in the Porsche Technical Specifications with the concentricity of the bore of the guide being within 0.025mm TIR.
We have achieved this level of accuracy by honing the bore and then cylindrically grinding the OD using a precision mandrel.
