I have a set of 906 heads I'm practicing porting on. I was reading David Vizards book that breifly deals with porting these heads and I have a few questions. He says that most of the air flow is on the outside wall and the roof of the intake port. How much material needs to come off here? Also he says to raise and widen the bowl area of the outside wall. Should the bowl be deeper and more rounded that the pushrod side of the bowl?
Also should I grind the valve guide in a 360 degree fashion or just sreamline the existing shape? As for the bowl area that leads up to the valve seat, does this need to be widened at all?
I have more questions, but this should get me started for now.
Thanks

 

Read this...
http://www.carcraft.com/techarticles...ort/index.html

Follow it to a "T". Then you can expect the same results they got.

 

You can raise the port roof 1/8" evenly on both the common wall and pushrod side of the port all the way from the port inlet to the blowl. The common wall can be straightened. It is actually fairly straight to start with compared to other stock heads.
You can streamline the valve guide boss and leave in the leading edge. You can create wider flow pathes around both sides of the guide boss deep in the bowl. The bowl itself can be blended and opened up to 85/90% of the valve seat diameter. Blend the short side radius to the seat. the floor of the port is good and only needs to be cleaned up.
The pushrod curve can be widened a bit. The port opening at the manifold is big enough. But you can raise the roof 1/8".

Match the intake to this. You may want to cut the opening of the intake gasket at the top to match this raised port if you're using a felpro 1255. The GM intake gasket is already larger than the port.

 

The GM intake gasket is huge! If I were to match the port to this gasket alot of material would have to come off the pushrod side wall. This doesn't seem like a good idea since Mr. Vizard says that most of the air flow resides on the outer wall. If I were to open up the pushrod side I would have to blend the rest of the port to match the opening, correct. Thanks for giving me a parameter for the roof and outer wall. I went all the way around the valve guide as Mr. Vizard did in his book, in the Car craft article the guide is left untouched on the long side of the bowl. May not be a big deal though it is only minor metal removal. I also did my combustion chamber the way he did, smoothing the quench pad and removing a little metal around the plug to give it a nice smooth contour. I will probably have the heads milled to get back some compression, the chamber work probably enlarged it by at least 2-3cc's. Thank's for your responses, they were very helpful to compare with. Now on to the exhaust......

 

"The GM intake gasket is huge! If I were to match the port to this gasket alot of material would have to come off the pushrod side wall. This doesn't seem like a good idea since Mr. Vizard says that most of the air flow resides on the outer wall"


I didn't say to match the port to the Stock type GM intake gasket. I just said it is much bigger than the port so no cutting of the gasket is nessessary.

I said the port opening is big enough but you can raise the roof 1/8" from the opening to the bowl.
Then match the intake manifold roof the the port.
then cut the roof of a felpro 1255 gasket to match this.
If you look at a stock vortec port roof there is a 1/8" beveled step in the roof right at the opening. This is the area that needs to be raised. The opening is actually only raised a slight amount.

Again exessive enlarging of the vortec port opening is not recommended or nessessary. It's not a flow restriction.

 

I'm sorry I wasn't implying that you wanted me to open up the pushrod side, just making a statement about the size of the GM gasket. I have slimmed the guides down in both height and width, I gave the outside wall some more room to breath and also leveled the roof nicely. Do I need to round the long side of the bowl? It kinda looks like a slope now. I have stared on the exhaust ports, radiusing them to my 1 5/8 header flanges. Should I blend the short side of the port to the lower opening of header flange or just radius the opening and clean the short side up a little. Thanks for your knowledge it has helped tremendously.
:hail: