Has anyone done it or is it a bad idea? I'm very tempting, but still a bit chickenish.

 

Not worth the gains for what you loose in guide strength and stability of the valve at high rpm, IMO anyways

 

Anyone tried it before?

 

Yes, I have done it to numerous race heads over the last ten years...with the original Honda guides as well as aftermarket bronze guides. I have not had to change any of the guides out yet and some have been in service for a long time. These motors regularly see revs above 8000 RPM and approach 9000 at some races.

I have just done it to a street motor (D16), but have not lit it up yet. It will be my daily driver - I just wanted some more long term wear information and figured this was the easiest way to get it.

Kirk

 

Would switching to bronze guides make it stronger. I don't really care about reliability issue, but I do want to rev to 10k. If the motor can last for 10k mile, I'll be real happy.

 

Just use the original factory guides...they are pretty damned hard. When I am porting and have to grind the factory guides it takes a lot longer than the bronze guides. I don't think you will have any problem getting 10K miles out of them.

Kirk

 

larry from endyn also tapers the valve guides.

 

Tapering is a little harder to accomplish than grinding them down to the roof of the intake runner - especially if you don't press the guides out and turn them down on a lathe. It does have the advantage that you have more support for the valve as the length of the guide can remain the same.

Kirk

 

Thanks for the encouragment, I'm going to do this for sure! Hi velocity port, here I come!