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Old 11-10-2013, 04:57 AM
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head porting.

been reading about the basics in this matter, folks have different opinions about it.
What is better rough or smooth finish?
1. Exhaust ports, smooth or rough
2. Intake ports, smooth or rough
3. valve cups, smooth or rough

some say smooth is not better
others say it is.

what is right, will smooth intake ports make gas build up in puddles in the ports?

Dont give me no math answers or you need flow bench to be shure.

Just the basics thanks

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Old 11-10-2013, 07:04 AM
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Non polished on intake and bowls. Polish is only eye candy.
Semi-polished on upper 2/3 of exhaust.
Neither do much without knowing where to cut and no flow device.
I see lots of ruined heads. I always call them by products of a "Monkey with a die grinder"
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Old 11-10-2013, 07:19 AM
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is that it?
Is there no reason for polishing and blending?
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Old 11-10-2013, 08:01 AM
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Lots for, but without experience or flow measuring equipment. You can make a large pretty port that flows less than a port matched stocker..
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Old 11-10-2013, 08:09 AM
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yeh heard that, but what about taking rough edges and smoothing, is that useless ?
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Old 11-10-2013, 08:45 AM
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Sharp edges are taboo and smoothing always help. Air flow in general doesn't like sharp edges or turns.
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Old 11-10-2013, 08:54 AM
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Another quick way to think about it, is, smooth big ports, are for top end running and big bore engines, because they pump the fuel to it, and haul.
Street stuff, is usually better to direct flow, and leave the runners slightly rough, because it helps break up the gas molecules for more power. And making the ports big, slows down flow. The moving air will travel mostly in the center of a port. How ever, if it runs into a sharp turn, and can't make the turn smoothly without hitting the other side of a port wall, that's where you have a problem.

ps: And if you have those nice smooth shinny ports, and it backfires, well, you now have coated smooth ports...Not slick and shinny ports.
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Old 11-10-2013, 09:31 AM
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well this tells me nothing about porting, guess i have to look in other places.
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Old 11-10-2013, 09:52 AM
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Maybe you should read it again. If you get nothing out of this, then maybe...you shouldn't try, or do it yourself.
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Old 11-10-2013, 09:58 AM
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ehhh i already started so its no turning back.
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Old 11-10-2013, 10:02 AM
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Never jump into the pan unless you know the heat is off...
Well, pictures of what you have may give us all an idea where you are at.
Always learn before you start. I hope you haven't went the wrong way, and can't fix it.
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Old 11-10-2013, 10:12 AM
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well sir with all the respect to you i like to learn as i go along
I dont have any pictures now but this is a 4 cylinder head DOCH.
Just playing in my garage you know like the most of you kids
I am using a dremel smoothing the ports and bowls.
and taking ruff molding marks away.
Not making any thing bigger yet.
I know its a small engine but to me the exhaust ports look kinda small to me.
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Old 11-10-2013, 10:13 AM
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Scroll all the way to the bottom of the page on this link. This is the book that will get you all set.
David Vizard's how to Port and Flow Test Cylinder Heads - David Vizard - Google Books
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Old 11-10-2013, 10:15 AM
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There are many reference books available, HP Books in particular, with motor builds, head theory and porting, etc. Barnes and Noble, Summit, JEG's all sell them.

Edit: Denny has you convered....
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Old 11-10-2013, 10:16 AM
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Quote:
Originally Posted by Braddi View Post
well sir with all the respect to you i like to learn as i go along
I dont have any pictures now but this is a 4 cylinder head DOCH.
Just playing in my garage you know like the most of you kids
I am using a dremel smoothing the ports and bowls.
and taking ruff molding marks away.
Not making any thing bigger yet.
I know its a small engine but to me the exhaust ports look kinda small to me.
Nothing wrong with taking ruff molding marks away. Just look at the way things flow through the port, and how they end up when entering the cylinder. Will the flow hit the wall, have to make a really sharp turn ?, or will it swirl around into the cylinder ? And the exhaust ports may look small, but, remember the flow rate. If you make them to big, the flow rate slows down. Porting in itself depends on where you want to make power, and how fast, when, you want to go.
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