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post #1 of 5 (permalink) Old 12-30-02, 02:48 AM Thread Starter
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Terminology question.

What does port matching mean?
Also, What does it mean to "O-ring" your block?

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post #2 of 5 (permalink) Old 12-30-02, 03:27 AM
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Port matching is to grind/polish the intake manifold ports to the exact size & shape to those in the head or vise versa giving an unrestricted path to the valves.
Same with the exhaust ports being cut pertectly to the extractor pipes.
O ringing refers to a circular groove about .25mm deep or less being cut into the block and head. A special gasket is used that once inplace & torqued is virtually leakproof ie locwire head gaskets


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post #3 of 5 (permalink) Old 12-30-02, 03:40 AM
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port matching is usually done by working each port ie the head and the manifold, to the gasket that is going to be used - in most cases this is the only way to "see" that the ports are in fact true to each other. Even the gasket must be properly aligned/trimmed to achieve the best uninterrupted air flow through the ports.

The "o" ring is usually made of copper or sometimes mild steel and is often incorporated into the gasket but not always.

A motor is "o" ringed to contain very high compression esp with blown engines. Quite often a solid copper (head) gasket will achieve the same result without the expense of machine work.
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post #4 of 5 (permalink) Old 12-30-02, 03:47 AM
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Oh, and porting is usually accompanied by polishing wherein the tracts from the valves to the ports are "sanded" or "polished" as smooth as possible to remove any roughness associated with the normal casting and machining processes. Very time consuming and sometimes difficult depending on the length and size of the runners, but the results are always measureable.
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post #5 of 5 (permalink) Old 12-30-02, 04:23 AM
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Port matching describes the process of ensuring that the inlet manifold and the inlet ports on the cylinder head are "matched" so that they are (1) properly aligned (2) have the same surface area and (3) the casting irregularities are smoothed.
The effect is to maximise air flow characteristics on the inlet side.
O-Ringing an engine block involves cutting a thin groove in the cylinder with a special tool and inserting a thin (often copper) wire into the groove that sits proud of the block by about 10 thou. This wire then comes into contact with the head gasket and forms a considerably stronger seal. Typically copper head gaskets are used as well. You usually find this work done on blocks that develop high compression ratios or which use forced induction (upwards of 12lb boost).
The same process can be used on cylinder heads as well.

Hope this isn't oversimplified.
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