harleyKmodel

Hi everyone,

I have a quick question about the porting in this pair of KR cylinders recently purchased.
In the following photo you can see the the valve guide has been trimmed down to be flush with the curve of the port, rather than protruding into it.
Whilst the guides do extend proud under where the valve cover would sit, what are your thoughts on this shortening of the guide within the port?
I have seen guides "smoothed" or better profiled in the port before, but not cut down like this.

Would it provide sufficient "guidance" or support for the valve stem, or do you think it was done at time of porting just to achieve a smooth curve
around where the guide would normally extend? I assume new guides will need to be installed anyway, but wondering whether or not doing the same again would be advisable.
Note I am likely to eventually run these with single springs and K covers - likely on a tuned motor for the street - so assume I would need to remove the guides to fit the upper covers anyway.

On my performance cylinders I run the cut down guide with no problems. Plenty of guide left to support the valve.

There does certainly appear to be a lot of meat left.

With no rocker arm side load like OHV there is minimal side thrusting going on with the Flathead valve/guide set up. So a little less support is OK in my opinion. It is debateable whether this actually increases flow to any considerable degree. I just couldn't resist cleaning the port completely on my radical engine.

I agree with Erik - there's plenty of guide to work with there. My '37 OHV Norton has shorter guides. And yes, debatable on effective performance - while flow is significant, valve timing is king - just ask Mr. Lienwebber. Cheers Hayley.