Port Matching Heads/Intake Gaskets

[ddewhurst]

Guys, asking the meaning of port matching was only a question because I didn't see a definition in the glossary or any meaning other places.

But reading rule 17.1.4.D.l. has it covered.

and external dimensions of the cylinder head or intake manifold MAY NOT BE REDUCED to facilitate internal porting.

Have Fun
David

[Banzai240]

Originally posted by ddewhurst:
But reading rule 17.1.4.D.l. has it covered.

and external dimensions of the cylinder head or intake manifold MAY NOT BE REDUCED to facilitate internal porting.

Again, you've lost me with your "reasoning"...

What do the "external dimensions of the cylinder head or intake manifold", have to do with the INTERNAL dimensions of the ports??



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Darin E. Jordan
SCCA #273080, OR/NW Regions
Renton, WA
ITS '97 240SX

[Greg Amy]

The "external dimensions" refers to the outline (external dimentsions) of the head.manifold. The purpose of this is to eliminate, for instance, milling back the face head .250 so you could, in effect, match-port 1.250" in...

[Tom Donnelly]

Ron,

Just pay someone with a flow bench to port match, otherwise you might do irrepairable damage to the head or make things worse. Without testing flow, you're just guessing about modifications to a critical part of the 'air pump'.

Tom

[Festus E. Simkins]

IMHO, I read the rules a little different than you do. I don't think they say you are matching the engine and maniford to the gasket. You are matching the two engine parts. Therefore, you would have to determine where the two surfaces don't match up and remove only the material necessary for each to mirror the other. This may mean that you remove material on one side of a port on the manifold and on the other side of the same port on engine block. I don't think it just allowes you to hog out the ports on both sides to equal the size of the gasket. You could however enlarge the gasket to fit the ports since gasket's are free.

However, I am probably wrong in this interpertation or maybe its something that has just gotten out-of-hand. Anyway, FWIW, the port matching situation like the ECU situation don't mean squat to me because I run a carb. 12A rotary. We can't do nothing to nothing.

Drive well.

[Geo]

Originally posted by Festus E. Simkins:
IMHO, I read the rules a little different than you do. I don't think they say you are matching the engine and maniford to the gasket. You are matching the two engine parts. Therefore, you would have to determine where the two surfaces don't match up and remove only the material necessary for each to mirror the other. This may mean that you remove material on one side of a port on the manifold and on the other side of the same port on engine block. I don't think it just allowes you to hog out the ports on both sides to equal the size of the gasket. You could however enlarge the gasket to fit the ports since gasket's are free.

The gasket is irrelevant. The rule places absolutely zero limitation on the matching process besides the 1" rule. You're adding words to the rule that do not exist.


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George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

[Quickshoe]

Festus,

I would agree that your interpretation is probably what the original rule writers "envisioned" and perhaps that was their "intent" but it is not what the rule says. And we don't know what their intent was, so we have to interpret the rule literally.

Besides, without knowing what the unmodified parts looked like how would one enforce your interpretation even if that is what was meant?

--edit can't spell worth a sheet



[This message has been edited by Quickshoe (edited November 10, 2004).]

[ddewhurst]

Mr. Jordan, please except my humble apologize for screwing up with my previous post.

***and external dimensions of the cylinder head or intake manifold MAY NOT BE REDUCED to facilitate internal porting.***

Have Fun
David

[Renaultfool]

Well at least Festus can read english. Glad to have you on my team! Let me try and explain myself more clearly.

"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.

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.

17.1.4.D states that "no permitted componant/modification shall additionally perform a prohibited funtion". I would argue that raising the top of the port beyond that necessary to eliminate any overlap areas, the matching allowed by this rule, would be an illegal modification because it could effect the air flow to the valve due to the change in the angle of approach of the column of intake air to the valve head. I have a 2.0 Ford racing modification manual from Dave Vizard that shows how to raise the port roof at the manifold face for that exact reason. That possibility eliminates the interpretation that it is "free" within 1". "Match" defines what you can do and sets the limit.

ITANorm mentioned adding an "anti-reversion step" at the intake manifold. Sorry Norm, 17,1,4,D, illegal function, unless the intake ports had this funtion from the factory.

Oh, yes, "match" as a verb, (1,a) "to encounter successfully as an antagonist". A truly fitting definition of what we are doing here in the off season.

[ITANorm]

Originally posted by Renaultfool:
Sorry Norm, 17,1,4,D, illegal function, unless the intake ports had this funtion from the factory.

I disagree. You may "gasket match" - to a free gasket - and you are not required to do it to both sides. For my particular car, it is irrelevant anyway. The factory 4AG engine has the "TVIS" (variable induction butterflies) plate between the head and the intake. It has been decreed by the tech department that it is not legal to modify or remove it (since it's neither part of the head nor the manifold), so doing anything other than cleaning up the (few and minute) casting dags to 1" in is pointless. Not to mention that the intake runners in a 4AG are too big in the first place.

[erlrich]

Originally posted by ITANorm:
You may "gasket match" - to a free gasket - and you are not required to do it to both sides.

Could someone please point out the section of the GCR that says you can "gasket match"? Not picking on you Norm, but I've seen this reference several times, and for the life of me I can't find it in my GCR.

<font face=\"Verdana, Arial\" size=\"2\">It has been decreed by the tech department that it is not legal to modify or remove it (since it's neither part of the head nor the manifold)</font>

Not trying to be argumentative Norm, but can you be more specific as to when/how this was determined. The reason I'm asking is that I've heard from several 240SX owners who said the butterflies could be removed as part of the matching process.

<font face=\"Verdana, Arial\" size=\"2\">Match means make both sides the same size.</font>

George, I have to disagree with your definition. In this context I believe match means to make both sides the same size as the other. I know it's a fine point, but I think the second you remove more material than necessary to make the ports "match", you have gone beyond what the rule allows. JMHO

Earl

[Banzai240]

Originally posted by erlrich:
...In this context I believe match means to make both sides the same size as the other.

How do you know which side to start with?? What if you slip and make one side bigger than the other... then can you "match" the the other side to fit??

The fact of the matter here is that there IS no clear definition of what the limits are, other than IN THE END RESULT, the ports should "match". Gaskets are free, so there is no limit there, and otherwise, the ports just need to be made to "match"...

Take that as you will..

Also, concerning the 240SX butterfies... which years are we talking about? Over the series of '91-94 and '95-'98, those butterflies were NOT installed in the factor on some years. The '96 intake that's on my car doesn't have them, but the '93 manifold that's on the shelf does, so I'm assuming that at some point in-between they were no longer being used by Nissan (if it happened to be in '94, then the '91-'94 would NOT be required to use them if you could get your hands on the'94 manifold...)

Remember also that, if these are part of the emmission control system, they can be removed legally as part of that system. Not quite sure what would be required to prove that, but I believe the rules allow for removal of all emmission control (EC) compenents. I haven't looked in my early shop manual to see, but there may be something in there that indicates if these were considered EC or not... It's worth a look...



------------------
Darin E. Jordan
SCCA #273080, OR/NW Regions
Renton, WA
ITS '97 240SX

[erlrich]

Originally posted by Banzai240:
How do you know which side to start with?? What if you slip and make one side bigger than the other... then can you "match" the the other side to fit??

Aw, c'mon Darin, this isn't Bill, you don't have to argue just for the sake of argument

I agree 100% that the rule is ambiguous, and open to several interpretations, but your arguments don't hold much water IMHO. Common sense says you start with the port that is smaller. And as far as what happens if you slip - well what happens if you slip and grind further than 1" into either port? Or for that matter, what if you slip and mill .010" too much off the head, and it is now under factory spec?

I think we'll just have to file this under "agree to disagree". Btw, has anyone ever heard of a protest being filed on the basis of "improper matching"?

Cheers
Earl

[ITANorm]

Sadly, the butterflies in the Toyota have nothing to do with emissions. They are there to increase intake velocity at lower RPM. There was no version of the 4AG the was offered in the MR2, AE86 or AE89 Corolla that did not have them. The determination was made in response to a query I posed to the SCCA Technical department about 3 years ago. According to them (Eric, I think is the one who actually commented), it also has to remain in the (LP)FP cars.

The good news is, according to dyno tests, they actually do some good - and removing them has, at best, a negligible effect on high RPM torque.

[Banzai240]

Originally posted by erlrich:
Aw, c'mon Darin, this isn't Bill, you don't have to argue just for the sake of argument

VERY FUNNY!

Common sense says...

Say no more... That is where you lose this arguement!

I think we'll just have to file this under "agree to disagree". Btw, has anyone ever heard of a protest being filed on the basis of "improper matching"?

I've never heard of a protest, but I can say with near certainty that the rule is as George and I have described... I personally wrote a letter to the CRB a couple of months ago asking this to be looked at for precisely this loophole/ambiguity in the rules, and the decision was returned that the rules were adequate as written, even given the issue we've been discussing. There is simply no way to make a ruling on this after the fact, because there isn't a clear limitation or definition on what a "port match" is...

I can tell you right now... those guys that are beating you and I are reading the rule the same way that I do...


------------------
Darin E. Jordan
SCCA #273080, OR/NW Regions
Renton, WA
ITS '97 240SX


[This message has been edited by Banzai240 (edited November 11, 2004).]

[Geo]

Originally posted by erlrich:
George, I have to disagree with your definition. In this context I believe match means to make both sides the same size as the other. I know it's a fine point, but I think the second you remove more material than necessary to make the ports "match", you have gone beyond what the rule allows. JMHO

Knock yourself out. I wish all my competitors read the rules the same way you are doing. There is no, none, nada, zip wording in the ITCS to limit how you match the ports. No wording saying you must leave one side untouched or even that you could only do minimal material removal.

I'll say it one last time (and if you still disagree, all the better for your competitors) that you're adding wording that does not exist.


------------------
George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

[John Herman]

BTW, everyone seems to be focussing on the intake side. Don't forget about the exhaust side. Free gaskets AND free manifolds. So in that light, do what you want up to 1" into the head. Even if you wanted to use the "strick" interpretation, you could make your own header flange that would match anything you did to the head.

[Ron Earp]

Well, I would have written and responded to the thread I started but I've just been too dang busy hogging the ports out on my head to take the time! ;-0

Interesting interpretation of the rule and not what I expected, but, I think it is correct in that it is very open the way it is written. No matter, I'm just matching up my larger gaskets and I'll call it quits.

Ron

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Ron
http://www.gt40s.com
Lotus Turbo Esprit
Ford Lightning
RF GT40 Replica
Jensen-Healey: IT prep progressing!

[lateapex911]

And without a real flow bench, thats the SMART thing to do!

Norm, you mentioned that the butterflies were there to increase intake flow velocity...which is to better atomize the fuel for a cleaner burn, right??? See where I'm going? Sounds like emission control to me! Of course, as you mentioned, they aren't hurting, so it's a moot point!

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[Ron Earp]

Originally posted by lateapex911:
And without a real flow bench, thats the SMART thing to do!

Clearly, you missed the sarcasim in my post. And, if so, plently of people can port well for good results WITHOUT a flow bench. And, I happen to be not so bad with cetain heads, this just isn't one of them

Anyhow, it is moot as all I'm doing is matching my gaskets. I've seen first hand on a flow bench what happens with bad work.

Ron

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Ron
http://www.gt40s.com
Lotus Turbo Esprit
Ford Lightning
RF GT40 Replica
Jensen-Healey: IT prep progressing!

[This message has been edited by rlearp (edited November 11, 2004).]