Hi, I have just got a race motor built for my F20c powered race car, The engine builder ( A respected professional who builds superbike engines) has raised the compression, crower rods, ported the head etc, after much discussion it was decided to shorten the valve guides, this was done as to lessen the restriction of the protuding guide into the port's, the guide roughly protrudes 10mm into the port. My question is has anyone else tried this? bearing in mind this is a race motor and the extra wear associated with this mod is not an issue as it gets regular checks/ rebuilds etc. Thanks

 

Take a picture of yours and let's compare.

 

I've tried to upload a photo but the admin has not enabled me to do so? How can I upload a photo, as the photo will explain it a lot better than me. Anyway the guides are flush with the port they do not protrude down the slightest, looking at your photo the guides seem to be shorted but not to the extent that mine are. Have you saw any gains on the dyno?

 

 

Better to taper the guides so they still provide the same over length to support the valves. Have a look at pictures on the Endyne site.

 

This is my head from Endyn. The yellow at the end is some grease.