Best Shape Around Valve Guide for Engine Flow

[philippeF]

Hello
May you tell me what is the best theoretical shape around a valve guide for best flowing in an combustion engine ?
best regards
Philippe

 

[Danger]

Hello
May you tell me what is the best theoretical shape around a valve guide for best flowing in an combustion engine ?
best regards
Philippe

Do you perhaps mean the valve face and seat, as opposed to the 'guide'? We might be using different terminology here, but to me the guide is the part that the stem passes through, and it has nothing to do with the flow.

 

[philippeF]

Do you perhaps mean the valve face and seat, as opposed to the 'guide'? We might be using different terminology here, but to me the guide is the part that the stem passes through, and it has nothing to do with the flow.

Hello
i mean in the intake pipe, around the valve guide...

 

[Danger]

Hello
i mean in the intake pipe, around the valve guide...

Okay. The only valves that I have personal experience with are in Mopar 'B' heads. The guide barely protrudes into the intake port about (3/16"), and is just a cylindrical extension of the head casting. Ideally, I supposed, it would be flush with the port wall and therefore have no effect at all on the airflow rather than merely very little as is the case now.
The intake runner and port wall should be as smooth as possible to prevent turbulence that would be an impediment, but the actual shape and length will depend upon what performance characteristics you want from the engine. Once the intake charge is entering the chamber, though, you don't want a smooth flow. A 'swirl' is necessary to maintain complete fuel atomization and ensure that the flame front progresses in the most efficient pattern. What that pattern is depends upon the combustion chamber and piston dome shapes, as well as spark-plug placement.
That's as far as I can go with it, since I'm neither a mechanic nor an engineer.

 

[philippeF]

Thanks, even if i have not the same opinion about polishing intake pipe..
regards
Philippe

 

[Danger]

Thanks, even if i have not the same opinion about polishing intake pipe..

You're welcome. I'm curious about your opinion regarding the intake runner, though. One of the simplest horsepower boosting operations when rebuilding an engine is 'porting and polishing', wherein you grind the port mouths and intake/exhaust runners to an exact dimensional match and smooth out any casting flaws or surface irregularities. The whole point of that is to reduce flow turbulence at the junction. It gives a big power boost for the outlay of a couple of Dremel bits and some emery paper.