Not incredibly experienced with porting but have done street ports (side) and peripheral ports.  The templates are needed for street and bridge ports because it ends up being an odd shape and the shape on the iron is all-important.  Of course, the same is true of the p-ports but the placement is effectively zero-dimensional.  It requires as much precision as can be had but it just starts with a point on the housing and has a specific diameter.  Assuming you are going round (instead of squarish) and and at 90 degrees to engine orientation, there's not much to the placement.  The caveat is your diameter will determine your port opening/closing so your placement and your diameter must both be planned. 

https://www.mazdatrix.com/pictures/11023.jpg
So these are big ports milled at an angle other than 90.  On the outside, it starts higher that where it actually ends up inside housing (where it counts).  Looks to be a 2" port.

http://i254.photobucket.com/albums/hh115/fd20na/13b-re%20rew%20race%20engine%20build/DSC02923.jpg
This is a semi-pport so it continues to use the side ports, too.  This one obviously centered right in the middle of the casting bullseye and are at 90 degrees but only a 1" port.

I won't tell you where exactly to poke the hole but there are some good examples out there that will allow you to precisely replicate placement.

Todd




On 2/6/2017 5:58 AM, Charlie England wrote: