porting defined

[ddoyle]

any one know where I could find some type of official description of what constitues porting and polishing? I have looked at a lot of rules for different racing, but found no real description. There seems to be plenty of personal opinions on the matter and I am not looking for more of them(sorry). The question, is porting the removal of metal only, or can metal be welded in then reshaped(is that still considered porting).
thanks,
dan

[GTJIM]

The Technical inspectors at race tracks usually regard ANY visible port modification as "porting" but many allow 'three angle valve jobs' that do not turn the corner into the port itself....
That being said; an intrepid little chap might do some port reshaping and do a surface finish that looked "as cast" - but I could not possibly comment ......

[JackJ]

Porting is removal of material from exhaust and intake ports of the cylinder head.Usually you would lay the exhaust and or intake manifold gasket on the head and trace the exhaust/intake holes of the gasket onto the head with a paint pen or grease pen.Then remove gasket and gind out the outer edge of the holes to match up with the line you drew on the head with a dremel tool rotary grinder..This is done gradually(tapered outwards) being carfull not to grind too much away.You then would use a fine polishing bit on the exhaust ports and the cumbustion chambers.The intake ports should remain a little rough to cause turbulance which better mixes the fuel/air entering the engine.

[jeff denton]

Do a search for "camoflage" and you'll see Rally Bob's post a few years ago about some pretty sneaky porting!
Some rules and techs will allow "port matching" if it doesn't go more than a specified distance from the gasket surface. "Porting" would be reshaping the tunnel beyond that.
Here in my Compact class none of it is allowed, nor checked...
We can do three angles of valve seat, though.
After the Compact Fifty the other night, first, second and third place were "pumped", first time ever, one may be a little bigger than claimed...

[RallyBob]

Originally Posted by ddoyle The question, is porting the removal of metal only, or can metal be welded in then reshaped(is that still considered porting).

Porting by definition would be the removal of material within the ports. Polishing would be the smoothing of the surfaces within the ports (polishing is typically for aesthetics and by my testing on Opel heads is worth virtually nothing in terms of airflow improvements).

Legality of adding material to the ports is something that a sanctioning body has to define. For example, the Sports Car Club of America specifically disallows adding material to ports (metal, epoxy, or otherwise) in most of their classes that allow porting. Many clubs/associations do not have this specific clause, but you'd be better off talking to tech officials about the legality of adding materials to a port.

HTH,
Bob