Short side radius head porting

[mag2555]

Hooding, sorry that I am just getting back to your question now.
This head I have pictured is a factory iron production head head with its stock valve size which is quite big for a non performance type head, and is the same as in the geometric drawing.

As such two of the main things the designers where looking for as a I have found out from discussions with them years ago was ( 1) to have the valve spread the fuel and air mixture around the perimeter of the chamber as well as possible.

2) have the head flow in the 200 cfm range by .450” lift to achieve there Hp needs.

The big valve and minimal 76 % throat size Attains both of those design needs pretty darn well.

Here is a picture of one of the many geometric templates I have on hand to guide my porting work.

There are 3 functions this template served to help guide you and also keep you from going off the rails so to speak size wise .
With these templates there is a perticular order in how to place them in the porting process, especially in heads where you can get up to large percentages of throat to valve sizes.
This is where thru the usage of this template pictured here and the short turn template in one of my earlier post can be used to prejudge what amount of port size increases will make the best of what you have to start off with.

Note the softend flat side of these template’s.
The flat side is cut back to 94% of the the overall diameter of the throat size wanting to be used.

This added flattened side allows the template to be used to do several things

1) size the throat.
2) size the width of the floor at the apex/ window area.
3) size the width of port at the apex from the floor up to the roof by using the 94% width of the template.

As reference, the first picture is a 1.850” template sitting down on the top of the valve guide in the iron head I have been using in all my pictures here.

Yes, to those of you who may ask, this is the same head as in that geometric drawing that started off with only a 1.60” throat.