Originally posted by Renaultfool:

"Match" is the defining word that limits the modification in my opinion, and it can be looked up in the dictionary for those of you who do not know what it means.
From the Websters Seventh New Collegiate, the definitions that pertain are, as a noun, (1,a) a person or thing equal or similar to to another, (1,c) an exact counterpart, (3,a) a process of matching, and as a verb, (3,a,2) to cause to correspond, and (4) to fit together.
this argument can be torn apart too. "thing equal or similar to to another" What's the exact definition of what similar can be? What's the specification of how close you have to make it similar? There isn't one. So if you took off 0.005" too much and it isn't a match i'm illegal? You can't expect exact tolerances so you have to have some variance allowance. But that isn't in the rule and shouldn't be cause it will make it ridiculous. This leads to my next disagreement with your interpretation.

Originally posted by Renaultfool:



Quickshoe,it would be very easy to tell if someone had gone too far. If you "match" them as Festus and I think it says, you would just remove the material necessary to line them up, remove the overlaps. This would mean that if one port is bigger than the other one all the way around, only the smaller mating port would be altered up to 1" from the manifold face to match the larger port. The originally larger port would be as cast and look like the rest of the unmodified port. If one port was offset from the other one, one port would be gound on one side and the mating port would be ground on the other side. The two unmodified halves would be as cast, look the same as the rest of the unmodified port. It would not even take any specilized tools, a visual inspection would tell, the same check that would be done for any other illegal porting.
The other thing you're missing is that not always is it a certain half of the port needs matching. Sometimes and a lot of the times there's flaws all the way around the ports on both the manifold and head that can't be matched to the other. Sometimes there's a slight curve on the floor, roof, wall of the port that you can't make identical to the other side without adding material, which you specifically can't do. And that's when you need to remove material from both sides to get them to match, which this rule allows for. And no one knows what your exact casting looked like before so it's not that easy to see visually if it's illegal. That's where the difference lies and the rule allows for. It's not always possible to "match" one side to the other and you can't even see that after the work has been done, so how do you tell someone they're illegal for that.

And 1" into the port isn't going to do anything performance wise.

And to the person that says you shouldn't do anything without a flow bench. Flow bench's are just as inaccurate and should be taken with a grain of salt as a dyno chart is. I can make a head flow 10% more than it did before at all valve lifts, doesn't mean it's going to make the car faster at all. It's just a means of comparison. You can make a head flow as much CFM as you want, it doesn't make it useful. Each head responds differently, and you can't see that in flow bench numbers.

One of the best quotes I heard from a well know head porter who has been doing them for a long time. A relative newb was talking to him about techniques and flow bench numbers of various heads, and the guy says "oh, you're a flow bench numbers guy. Yeah, well I'm a track times guy. That's how I build heads." Great quote and should always be remembered. A flow bench is a tool, but only one tool and usually doesn't tell the whole story.

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[This message has been edited by stevel (edited November 16, 2004).]