I have seen that in some ported/polished cyl heads, some people actually grind the valve guides down so they are almost flesh with the chamber hole. What is the point of doing this? Would this hurt anything, effect anything? If it doesnt, I am going to grind mine down, this would make my port/polish much much easier :)

its done for a couple reasons. Its slightly easier to port the bowl area. It is also better for airflow. Its easier for air to flow around the valvestem than is is to flow around the guide that is 2X the size. How much of a difference does it make? I dont know. Some port jobs leave it in and some dont.

Terry

Originally posted by Star Turbo Talon
its done for a couple reasons. Its slightly easier to port the bowl area. It is also better for airflow. Its easier for air to flow around the valvestem than is is to flow around the guide that is 2X the size. How much of a difference does it make? I dont know. Some port jobs leave it in and some dont. Terry

So in reality, it doesnt hurt anything to do this then. If it doesnt effect any performance or cause any issues w/ the valves, I am going to just grind it down flesh with the bowl area, this will make porting much easier for me.?

In theory, it can affect the longevity of the valve. Less support. Though I have never tested out this theory myself, it was the "rule of thumb" for racers "back in the day" (if that's not wishy washy enough for you :P ). I say this just because you ask for possible drawbacks of doing this.

It was hard to say how true this was because the people that did this generally were more hardcore racers that tore down their engine before the valves had a chance to test the theory. I personally like the idea but then I'm not afraid to have to break my engine back down because of it :shrug

MB

Yes grinding down guides will increase overall flow through the port itself, but will increase wear on the valves and will eventually start to burn oil, we are actually working on getting tapered valve guides made up for the 420a since we are going to be offering CNC ported heads and need a smaller guide area for the enlarged port and also for people like yourself who want to increase more flow without having to grind the hell outta them, just pop them and an they would be flush with the ports, whether or not they are going to be just made for our cnc ported heads im not sure on...