Port Matching Heads/Intake Gaskets

[Ron Earp]

Before I do something bad I just want to check it here.

I have my head off my motor so that I can re-ring the pistons. I've got new gaskets and the new gaskets, like the old ones, are larger than the intake and exhaust ports of the motor. Figures, Lotus is not known for quality castings, that is for sure.

Now, I read the rules that I can port match these things so that they match the gaskets and that I can do so for 1" into the head. I intend to do this and it would appear that it would help flow out quite a bit. But, porting and polishing are dis-allowed.

I do not want to run afoul of the rules or get in trouble if protested. So, if I port match these things and blend them in for one inch that is legal, correct? I'm just concerned that if someone looks at it they'll say "porting, illegal!".

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

[Bill Miller]

Ron,

You've got a pretty good handle on the rule. What you are considering is legal.

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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608

[Renaultfool]

Ron, that is not what the rule says.

There is a difference in "port matching" and "opening a port up to the size of the gasket"

D,1,I allows for port matching only. Gaskets are free therefore it doesn't make logical sense to allow you to open the port to "any" gasket. All you would have to do is buy a bigger gasket.

To legally port match, the port on one side of the gasket surface would be untouched assuming one port was smaller than the other, or some area of both ports would be untouched if the ports are offset.

Hogging the ports out the the size of the gasket hole 1" each way from the manifold surface would not be legal according to the rule book in my opinion.

[ITANorm]

Originally posted by Renaultfool:
Hogging the ports out the the size of the gasket hole 1" each way from the manifold surface would not be legal according to the rule book in my opinion.

Not to mention that it would be counterproductive in most modern engines.

[Banzai240]

Just a point from a previous discussion, but since Gaskets are free, you are allowed to use ANY intake gasket.

It has been successfully argued that because of this, there is no requirement to have to port match to a FACTORY sized gasket, so in essence, you can open up the ports at this point (up to 1" in on either side), to ANY gasket you choose to use, including one with much larger port openings...

I wrote a letter on this, thinking it was a loophole that needed to be either closed or better clarified, but the rule was deemed adequate as written...

So, read your ITCS carefully before taking this to heart, but the way the current rules are written, there is really no limiting factor as to how much you can "match" your ports... You can pretty much pick a gasket, and open the ports up to whatever point you deem appropriate...

Like some others have said, however, on a more modern engine, you are likely to go backwards if you play too much with this... They are pretty well cast from the Factory (speaking of Nissans, Toyotas, Hondas, etc.. mostly... Others may vary...)

Good Luck,


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


[This message has been edited by Banzai240 (edited November 08, 2004).]

[Geo]

Darin is quite correct on this one. Match the ports to any size you like.


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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

[Ron Earp]

Originally posted by Renaultfool:
Ron, that is not what the rule says.
There is a difference in "port matching" and "opening a port up to the size of the gasket" D,1,I allows for port matching only. Gaskets are free therefore it doesn't make logical sense to allow you to open the port to "any" gasket. All you would have to do is buy a bigger gasket. To legally port match, the port on one side of the gasket surface would be untouched assuming one port was smaller than the other, or some area of both ports would be untouched if the ports are offset. Hogging the ports out the the size of the gasket hole 1" each way from the manifold surface would not be legal according to the rule book in my opinion.

After reading the rule over I disagree. The rule indicates that I can match the ports to the gasket and that is fairly simple. My gaskets, as delivered and it is what is available from Delta Motorsports, the only Jensen place around, are about 1/8" larger than the ports all the way around. It is clear looking at the intake maniold size, and the head size, that the head opening is smaller than the gasket and the intake manifold.

Now, if I take a tool and grind away some of the head to match the gasket that is port matching. But, you can't simply grind the head out to the opening leaving a 90 degree step just like you had in the first place. Therefore, you need to blend that ramp up a bit to make a smooth transision into the intake passage. Hence, the allowance for distance.

I'm not working the bowls, altering the intake exhaust floor, or anything like that, just trying to make a relatively free path for air to enter the engine and I think this rule allows for that. I imagine you fellows with late model stuff this is a moot point. I was in a machine shop a few weeks ago that had a BMW 24 valve head on the floor and I was amazed at the size of the ports and the quality of the castings. Mine looks like someone cast the heads in a sandbox.

I suppose one could go crazy with huge gaskets, but, I don't have that option. I'm lucky to get A gasket, much less have a pick of a litter. I think that Darin has the rule right, whether or not that was intended is a different story.

Ron



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

[Geo]

Originally posted by rlearp:
After reading the rule over I disagree. The rule indicates that I can match the ports to the gasket and that is fairly simple.

Actually, the gasket has nothing to do with this rule. You can port match up to 1" from the mounting surface. Hog it out if you like.


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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

[lateapex911]

remember Ron, gasketsare free...in a pinch I have made my own...sooooo, it really opens up the rule to more of a "do whatever you want as long as you go no further than an inch".

That said, it is proabably unwise to get carried away here, unless you have a flow bench!

Also, the discussion of how you measure that inch has arisen here before...you can imagine that arriving at a consensus was impossible!



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

[Mark LaBarre]

Originally posted by rlearp:
...., are about 1/8" larger than the ports all the way around. ...

That's no different than any VW out there. Grind away.

[Mark LaBarre]

Originally posted by rlearp:
...., are about 1/8" larger than the ports all the way around. ...

That's no different than any VW out there. Grind away.

[Renaultfool]

As technical and picky as some of the discussions on this site get, I am amazed that this one seems to fly. What happened to the "if it doesn't say you can, you can't" philosophy? How does the rule indicate that you can "match the port to the gasket"? I can't find the word "Gasket" in D,1,I, the section that allows port matching, therefore to me it seems a pretty liberal interpretation to assume that you can match the port to the gasket or make the port at that point any size you want. The rule as printed allows you to match the port in the intake manifold to the port in the head, which is a little more difficult to accomplish than just hogging the port out to the gasket hole, but that is what the rule says in my book.
I would think that raising the roof of the port 1/4" through "matching" for instance, allowing the air flow a better angle to the valve head, (if your head happens to have a short port length due to the 1" limitation), would be much more of a performance advantage than the improper sized windshield washer bottle, an argument I have seen on this site before.
If it "has been successfully argued" print it in the book. If it doesn't say you can, you can't, right?

[Geo]

Originally posted by Renaultfool:
As technical and picky as some of the discussions on this site get, I am amazed that this one seems to fly. What happened to the "if it doesn't say you can, you can't" philosophy?

Nice idea. But if it says you can, you bloody well can.

Here is what the rule says:

"Manifold and cylinder head port matching is permitted. No material may be removed further than (1) one inch in from the manifold to cylinder head mounting face(s)."

Originally posted by Renaultfool:
How does the rule indicate that you can "match the port to the gasket"? I can't find the word "Gasket" in D,1,I, the section that allows port matching...

It doesn't.

Originally posted by Renaultfool:
...therefore to me it seems a pretty liberal interpretation to assume that you can match the port to the gasket or make the port at that point any size you want. The rule as printed allows you to match the port in the intake manifold to the port in the head, which is a little more difficult to accomplish than just hogging the port out to the gasket hole, but that is what the rule says in my book.
I would think that raising the roof of the port 1/4" through "matching" for instance, allowing the air flow a better angle to the valve head, (if your head happens to have a short port length due to the 1" limitation), would be much more of a performance advantage than the improper sized windshield washer bottle, an argument I have seen on this site before.

Ah yes, but now you are adding your own words to suit your own sensibilities.

The rule says you may port match. The only limitation placed upon this is the 1" rule. There is no limitation that say only one side may be machined, therefore both sides may be machined and to whatever size your heart desires.

If it says you can you bloody well can.


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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

[lateapex911]

Right..........

And the limiting factor would be the gasket....except gaskets are free....soooo, therefor, ergo, and all that, there is no pactical limitation....except what helps and what hurts flow.

[Banzai240]

Originally posted by lateapex911:
...except gaskets are free....

You know, I must be doing something wrong, because everyone keeps talking about "free gaskets", but I keep having to pay for mine...





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

[ddewhurst]

Port matching....... Hmmmmmmm

What is the meaning of port matching & where is the definition ? Can I weld some material to either piece or both pieces within the 1 inch & reblend to match ?

Have Fun
David

ps: I may have missed the definition of port mactching.

[Banzai240]

Originally posted by ddewhurst:
Port matching....... Hmmmmmmm

What is the meaning of port matching & where is the definition ? Can I weld some material to either piece or both pieces within the 1 inch & reblend to match ?

Isn't there something in the ITCS pertaining to adding materials being a no-no?? I'll have to go check...

DJ

[Renaultfool]

Ah, yes, but my Webster's defines "match" as "to make fit", not hog out. The word "match" itself defines the limits of what you can do, blended 1" each way from the manifold surface. The blending 1" was to limit how far you could go into the port to discourage porting. "Match" would be the definition I gave in my first post. You can line them up and blend the small amount of material removed lining them up into the port wall to a maximim of 1" from the manifold face, but I do not think that means you can remove more material than necessary to line them up. That does not make any sense given the strict interpretations used in most other posts on this site. Show me a definition where "match" is equal to "enlarge" and I will buy it, otherwise I am curious as to how you come to your conclusion from the wording in this section.

That may differ from current practice, especially according to the feelings expressed here, but that does not change the definition. Using common english definitions I do not see where it says "you can hog it out."

"If it says you can, you bloody well can" but if it doesn't, you can't.

Sorry boys, we have to live with what the book says, not what we want it to say, at least until we change the book.

[ITANorm]

From Norm's Unpublished Dictionary of Automotive Terms in Common Use:

Port matching: (verb clause or noun clause) The act of (or an item that has been) altering the size of head or manifold ports to more closely resemble each other in a cross-sectional plane; usually consisting of removing material from one or both sides to attain symmetry. (Note: The ports in the head are usually left somewhat smaller on the exhaust side, and made slightly larger on the intake side than the port in the mating surface to provide an "anti-reversion step".
__________

So, you could add material, but I think the "no material may be added" may trip you up.

[Geo]

Once again you're adding wording. Match means make both sides the same size. There is no limitation placed on this other than tehe 1" in rule.

If it doesn't say you can, you can't. However, if it says you can, you bloody well can. Now, if it says you can and places limits on it, you have to work within those limits. There are no limitations placed upon the size of the ports. Have at it. Probably make things much worse anyway.


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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