Hi everyone,

I'm in the process of porting my heads. My question is: I've done a pretty extensive job of smoothing the valve guides in the bowl. I've got them down pretty close to the brass valve guide insets. I'd like to know if I can grind down the guides (brass insets included) so that they don't protrude into the bowl as much. I've seen some high performance aftermarket heads on which the valve guide barely sticks out into the bowl at all. Can I grind the whole thing down to be a bit more like that?

I'd really appreciate anyone with the experience/knowledge helping me out here.

 

What castings are you using? Head/runner design will dictate how much you can safely remove. A shorter guide can sacrifice durability, so you may be trading 1-2 CFM at peak flow for guides that wear out faster. It may be better to shape the guides into a cone that blends into the valve stem less abruptly than the raw casting. This will reduce the disruption of flow as much as possible while maintaing the maximum guide length and strength.

 

Thanks for the input Vader. I'm using 601's so that are pretty nicely ported now. The valve guides are grinded down smooth to the point where they are completely conical - practically right to the inset at the tip. To be honest, I really can't see much flow improvement from taking it down a bit ...but while I have the heads on the bench... I've got about 20 hours of work on these so far, so they're pretty smooth now - lookin' good.

I am curious about how close I can grind down to the inset as well. I can leave a little lip there, or I can go right down so that the guide slopes right into the valve stem (when looking at in from the intake side). I know that would improve the flow, but I'm wondering about durability as well there. I've seen some ported vortecs where the guide was grinded right down to the inset, and the inset itself grinded a bit to match. Any problems with that?

 

If you leave the bronze alone, and blend the iron surrounding it to a smooth transition, everything should be fine. The valve has to come out somewhere, and having a plain square intersection where the valve meets the head may actually cost you some flow. Guiding the air flow around the valve stem intrusion would be better.

Shortening the guide length will almost certainly make it easier for the valve to be tipped by the rocker action and wear the guides sooner.