Valve Guide Geometry

[chris_seven]

I have just had some Valve Guides arrive from Serdi. They are manufactured from Manganese Bronze and are about 53.2mm long.

The standard guides that I have measure around 51.7

The Serdi guides have a locating shoulder which would mean that the portion of the guide that takes the stem seal would stick out around 14.9mm above the head.

As the spec calls for 13.2mm - 0.3, I am concerned that they may interfere with the valve particulary with high lift cams such as GE100 or similar.

Does anyone have any data?

Also is it sensible to shorten the portion of the guide that projects into the port or will this reduce heat rejection from the valve?

[Henry Schmidt]

I too have seen some guides that are extra long at the spring end and they will cause issues. Not only do you experience rocker damage when the retainer bottoms out on the top of the guide but even without bottoming on the guide the retainer ruins the seal.

Shortening the guide will reduce heat transfer and guide life so when we are concerned with port flow we machine the guide with a slight tape calculated to start where the guide leaves the heads.

[chris_seven]

Henry,

Thank you,

I will shorten the guides at the spring end as we are planning to use RSR cam profiles.