I am in the preliminary stages of porting my end plates. I have included a pic of the stock port and I have shaded the area that I am going to port. This port design looks fairly conservative IMO and I'm not sure how far to take it (length and width). The width of the port currently measures 12 mm from the inner edge of the coolant oring groove. From what I understand I can port the width up to 10.5 mm from the coolant oring groove, but then corner seal support starts to become an issue. I figure I can widen my port another millimeter, but that is about as far as I want to take it. I have a couple of existing port designs (KD and PFS) that got me where I am right now, but I wanted some opinions from some of the guys here who have some experiencing with porting. I tried getting a hold of one of Ito's port templets but it doesn't' look like that is going to happen and I want to get this motor together in the next two weeks or so.

 

That is pretty mild. You can take the port much higher if you bevel the top of the port edge outward to avoid cutting into the water jacket.

 

Are there any other opinions on this port? Can anyone let me know how far up I can port these housings? Please feel free to mark up the diagram in paint to illustrate how large a "large" street port really is.



Thanks

Josh

 

Here would be my style of porting it. I like a broad power band but late closing ports (round top taken high with an outward bevel).

 

thanks for your help! I'll start porting these housings this week. I'll sure you'll here from me if I run into any snags. I think I will be ok since I have ported housings before but I just haven't done anything on the large side yet.

 

Ink up the whole port area. Assemble a rotor with one corner seal held in the hole with two sided tape. Bend up the end of one side seal spring into a 90 degree angle

to act as a scribe. Install the bent spring in the groove with the 90 against the corner seal. Turn the rotor backwards through the port area to scribe the line that shows the leading end of the side seals. Remove the spring and install it with the 90 against the other side of the corner seal. Turn the rotor in the running direction to scribe a line to show the track of the trailing end of the side seals.



In stock form, both ends of the side seal are supported on the iron. As you widen the port to the intake manifold side, the trailing end of the side seal will fall off at the bottom of the port and regain the iron at the top (closing) of the port. The trailing end must not touch or climb up on the outer line of the port. Leave it off untill it gets to the closing line. Radius and polish the whole closing line so that the side seal will not be damaged.



The outer line is the track of the leading end of the side seals. There are two ways to go here. You could cut away iron to the edge of that line, and still have room for a narrow bridge port later on. You could leave as much as in the picture and still have room for a big bridge port later on.



The big change is the later closing of the port. (like a cam with more timing) In this case later intake closing point. So you get a big degree wheel and lay out the closing point yourself, or buy a mask from a known builder to copy their port shape. Racing Beat or Mazda Trix maybe. Go to Paul Yaws web site and read the tech series.



Go easy. Its a lot better to go in later and cut away some more iron than to scrap the iron and start over.



Lynn E. Hanover

 

Primo info Lynn. You da man...

 

Lynn, i got a question, i just did this on a 6-port housing and the secondary port does not support the trailing edge of the side seal, but by the division to the aux port it is supported and stays so all the way after that. I'm nearly positive its not supported because the upper edge of the secondary port kept bending over the corner seal spring so that it would not scribe from there on out, so i had to scribe from the top down to trace the top line.

 

The point was that the side seal just should (land) on the flat after the port closing line, rather than have the round part of the upper outer corner be closing from the side and pinch the end of the seal. So if the end of the seal is unsupported as it crosses the opening, leave it off. Let the closing line bring it back on the flat with a radius and a polish job. If you have to move the manifold side of the port over a bit. Just enough so that the end of the seal is off until it gets to the closing line.



Notice that the port in the picture from the earlier post, has the upper outer corner rounded off too much and the track of the end of the side seal comes in contact with the side of the port before it gets to the closing line. That is not how it should look. The black line is what you want. To keep the end unsupported until it gets to the closing line at the very top of the port. To get the closing line angle just right. Scirbe a line along the edge of the rotor where you want to close the port. Look at that line. If the side seal gets to that line as the closing line, the whole unsupported length gets there at the same instant. Bad Mojo. What if the blades of a scissors came together all along their length at the same time. You would have a hell of a time getting them to work, right?



So, move the inner end of the closing line down 1/16" and raise the outer end 1/16", now the inner part of the unsupported side seal comes up on the flat first, and like the scissors, the tip end comes up last. Very smooth. Great seal, long life, no damage. Most if not all would be reused at overhaul.



Radius the whole closing line and polish it.



The poor drawing is of the (painless) closing line. Note the scissors line on the right. On the left is what almost everyone uses. See the problem? The small change in the angle of the line has no affect on performance or timing.



Lynn E. Hanover

 

Thank you! great info. (runs off to change the closing geometry on his ports)