Port Design

[Nick Campagna]

I have been considering the time and effort people go through to port a head. Here is my question: Why not cast a port, remove the plug, Then recast around the plug in plaster., remove the plug. Now we have a cast of the port that can be put on the flow bench, flowed, and modified at will. Make a mistake and repair with plaster. Really screw up and make a new port. Needless to say, plaster can be replaced with a polymer of choice, like they cast desk ornaments in. This also allows the porter to visually inspect flow patterns with smoke, atomized dye, etc. What am I missing ?

[howieschoon]

This sounds like a decent idea. The only thing that seems like it could be a problem would be if the plaster (or whatever else was used) was very porous and would let air in through the port walls or something of the sort. I'm surprised that no one has commented on this yet. It would think that there would be a good way to develope a port without the posibility of ruining an otherwise good head.
Howard

[Nick Campagna]

Porosity could be eliminated by the use of spray on Krylon clear. Used it once on a new bar of soap and left it in the bathroom for the family and left for work. Interesting results occurred.

[Stan Weiss]

Unless you have blueprints of the heads when making the molds, you can run into surprises like water and bolt holes when you move from you plaster port to the head.

[Nick Campagna]

Absolutely, this is why we have sonic testers. Also, the Radon inversion formula, developed at the turn of the last century for astronomers, was later used by Dr. Hounsfield (ph) to develop Computed Tomography. Industrial CT scanners can recreate the profiles quickly, and are not that expensive considering the results. All examinations will of necessity not consider core shift on heads, and some repair might be needed if on the bleeding edge. If one draws circles around the stock ports every 1/4 inch from flange to valve head, a fairly accurate map of wall thickness can be developed with a sonic wall tester.

[BlackCat13]

Ports have divergent and convergent cross sectional shapes/areas.
Any port mold would have to be flexible enough to remove from the actual port shape.

Also, some porters say that .010" can make a difference in flow in critical locations.

[big block fiero]

Originally Posted by Nick Campagna

Porosity could be eliminated by the use of spray on Krylon clear. Used it once on a new bar of soap and left it in the bathroom for the family and left for work. Interesting results occurred.

I just love this site, so many tips and ideas!

[Nick Campagna]

This is the port molding material some people use. I agree that it must be flexible AND dimensionally stable.

Making Molds for Porting Cylinder Heads - FordMuscle Magazine

[comp]

Originally Posted by Nick Campagna

This is the port molding material some people use. I agree that it must be flexible AND dimensionally stable.

Making Molds for Porting Cylinder Heads - FordMuscle Magazine

good link