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Old 10-31-2012, 09:19 AM
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Head Porting Question

Hello,
Well beginning another engine build for one of my trucks and currently doing some work on my cylinder heads. Usually when I do any porting there is not much metal removal. I knock down imperfections and sharp edges in bowl area, short side radius and clean up said area's without getting crazy just enough to improve but not ruin a good set of heads. On the runner side I try to stay about 1-2 inches from runner opening of the head only to remove casting flash and lightly shape opening as most SBC heads are pretty funky here as most of you know. Recently I was speaking with a dirt track racer who informed me that if I "polish" out the intake runner wall that sits on the cylinder wall side it will improve flow,not puddle and help create a better "swirl" heading to the cumbustion chamber. Has anyone heard of this and is it factual or fiction? A lot of the "roundy-round" guys have decent tips with this sort of thing and he seemed knowledgable so my curiousity is up. Thanks guys.

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Old 10-31-2012, 01:16 PM
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I've heard that polishing gives a smoother flow, but i also heard that the disturbance caused by having rougher walls will actually increase torque. Maybe someone on here has actual proof of either of these?
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Old 10-31-2012, 01:36 PM
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After doin' this stuff since 1958, I still learn new tips and tricks every day. Generally speaking, if you study fluid dynamics, you will understand that there is a boundary layer right at the surface of the port (or any surface where fluid or air passes over it) that can be as rough as a fingernail file and not make any difference to flow. If you stand at the bank of a river, you will see the main flow going down the middle, with the flow slowing way down at the bank of the river. Thinking up to this point is that you should leave the surface rough in the intake port in order to help the airflow pick up fuel that has dropped out of suspension, while polishing the exhaust ports.

Like I say, this has been the general concept for a few years, but people find ways every day to get more flow into the cylinder and maybe this fellow is one of those people.

What I'm sayin' here, is don't call anybody a liar or disbelieve what they say until you go through the same processes that they have and found them to be lame.
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Old 10-31-2012, 06:40 PM
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Quote:
Originally Posted by techinspector1 View Post
After doin' this stuff since 1958, I still learn new tips and tricks every day. Generally speaking, if you study fluid dynamics, you will understand that there is a boundary layer right at the surface of the port (or any surface where fluid or air passes over it) that can be as rough as a fingernail file and not make any difference to flow. If you stand at the bank of a river, you will see the main flow going down the middle, with the flow slowing way down at the bank of the river. Thinking up to this point is that you should leave the surface rough in the intake port in order to help the airflow pick up fuel that has dropped out of suspension, while polishing the exhaust ports.

Like I say, this has been the general concept for a few years, but people find ways every day to get more flow into the cylinder and maybe this fellow is one of those people.

What I'm sayin' here, is don't call anybody a liar or disbelieve what they say until you go through the same processes that they have and found them to be lame.
I agree 100%. I found it interesting because what he was saying made sense, if one side flows faster than the other it would help create a swirl leading to the cumbustion chamber. I tried to google this to see if anyone else has talked about it and couldn't find anything, so I thought maybe someone on here may of heard of or even flow tested this before. Those guys running strict class cars with stock/oem components tend to have the best methods of squeezing out every last little bit of power they can and like I said he seemed very knowledgable. Not sure I want to try it on my heads without feedback from a few folks with experience doing this as I was always told not to polish any part of the intake runner itself. None the less it sounds like an interesting theory and thought I should inquire and share.
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Old 11-01-2012, 11:16 AM
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the surface finish is relatively meaningless, BUT enhancing port bias is not. It doesn't need to look pretty to do a good job though, the finish left by a carbide bit is adequate.

On a side note, screwing with the port entrance as you have is worth very little if anything on heads that have not had a good valve job and bowl work done. In fact you can see in many race heads where the areas you enlarged are somewhat filled in- depending on the application.
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