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Old 05-05-2010, 11:39 AM
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Head Porting question.

I plan on getting a cylinder flowed so I can go with a new cam. But I was wondering what you thought about this bit of material behind the guide on the cylinder side. Should I keep it, or grind it out? I can venture that taking it out would cause a low pressure space behind the valve. But on the other hand, the collision of air there after might help with swirl. What do you think?





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Old 05-05-2010, 02:29 PM
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Quote:
Originally Posted by leadfootdriver
I plan on getting a cylinder flowed so I can go with a new cam. But I was wondering what you thought about this bit of material behind the guide on the cylinder side. Should I keep it, or grind it out? I can venture that taking it out would cause a low pressure space behind the valve. But on the other hand, the collision of air there after might help with swirl. What do you think?




What is the head? With a Vortec style port shape where the bottom of the port is wider than the top keep it. If you ported according to David Vizard's books on a conventional rectangular port, removal will help the swirl on those.

Bogie
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Old 05-05-2010, 03:51 PM
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Bogie, this is a SBF head, Holley head if IIRC. I would keep the vane but make it smaller. it is too long/tall from the guide toward the seat. This is especially noticable in the second picture, it is taking up too much space as the air is trying to join back up after it has split around the guide and valvestem before it gets to the valve seat.
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Old 05-05-2010, 04:12 PM
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Quote:
Originally Posted by ericnova72
Bogie, this is a SBF head, Holley head if IIRC. I would keep the vane but make it smaller. it is too long/tall from the guide toward the seat. This is especially noticable in the second picture, it is taking up too much space as the air is trying to join back up after it has split around the guide and valvestem before it gets to the valve seat.
Yeah, I went back and looked at at the chamber and sure enough if that isn't a Chevy 265, it's a Ford. Time for new glasses.

Bogie
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Old 05-05-2010, 04:21 PM
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It is a good idea to make the vane smaller, to improve flow widen the area
between the guide and the port wall like this. Create a good flow path on
each side of the guide, don't be afraid to remove material from the valve
guide boss.

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Old 05-05-2010, 06:18 PM
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THanks for the replies.

I have to say, I'm so tired of messin' with these heads!

It's a sure thing that my next set of heads will be CNC'ed!

These heads seem to be different in what I've seen in that, the valve guides are laid down in line with the port. So, there's only so much material I can take off without exposing the guide. But whatever...
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Old 05-05-2010, 06:50 PM
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Don't get tired now, you have only just begun. Don't be afraid to expose some
of the guide and widen the port in the turn. Look at that second picture you
posted, the port cross sectional area at the guide is too small.

Those are really nice heads that just need a little work to get them flowing.
To do it right you will need a way to measure the valve pocket and get it sized
right in relation to the valve OD and throat size.
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Old 05-05-2010, 07:36 PM
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Quote:
Originally Posted by automotive breath
Don't get tired now, you have only just begun. Don't be afraid to expose some
of the guide and widen the port in the turn. Look at that second picture you
posted, the port cross sectional area at the guide is too small.

Those are really nice heads that just need a little work to get them flowing.
To do it right you will need a way to measure the valve pocket and get it sized
right in relation to the valve OD and throat size.
'Think so? The volume on the intakes are about 175 CC's measured this afternoon. I have a little 306 motor.
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Old 05-05-2010, 07:43 PM
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The idea is not to get the port bigger for the sake of being bigger, it's to get
them to flow to there potential. It's important to get the cross section of the
port correct in the turn, pocket and throat area; that with a good valve job is
what will make power. I have ported these heads before, real nice port but
needs work.
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Old 05-05-2010, 07:58 PM
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Quote:
Originally Posted by automotive breath
The idea is not to get the port bigger for the sake of being bigger, it's to get
them to flow to there potential. It's important to get the cross section of the
port correct in the turn, pocket and throat area; that with a good valve job is
what will make power. I have ported these heads before, real nice port but
needs work.
So I should bring the short turn down a bit?
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Old 05-05-2010, 08:07 PM
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Quote:
Originally Posted by leadfootdriver
So I should bring the short turn down a bit?
I don't recommend working the short turn with out a lot of experience. Get
a set of snap gauges and measure the throat, pocket and port width just
above the guide.
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Old 05-05-2010, 08:50 PM
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Like AutomotiveBreath has said, there is a lot more material that can come off the sides of the guide boss, the boss really doesn't need to be much wider than the guide itself for the most part, and the port needs to be wider overall to each side of the guide to make up for the space that the valve guide and the valvestem are going to occupy then they are assembled. You don't want to mess too much with the short turn, it already isn't tall enough right out of the cast mold really, but raise the roof of the port as this is where the flow is.

Don't think of it as trying to force it to flow where you want, but to open it up where it already wants to flow.

Don't worry about swirl, Ford heads don't exibit much swirl, they are more of a tumble form to the air coming into the cylinder, like tripping and falling down a flight of stairs, end over end tumble into the cylinder.
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Old 05-05-2010, 09:28 PM
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Okay, I think I get it. There's a lot of extra material on the left side of the port here where I drew the line. I tried to get a good pic of it, but it easier to see in person. Looking at it, you can see that it's very congested, and not symetrical with the right side. But I don't think I can get away with taking to much away here as the water jacket is on the other side. I wish I knew how thinck it was. I can't really see with the flash light.

This port is the worst. The other head was cast the same way.

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Old 05-05-2010, 09:52 PM
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At the middle arrow remove material from the port wall and the guide boss.
At the top arrow remove material from the port wall. Little needs to be done
at the bottom arrow. Do this on both sides of the port, if you remove a little
material from each surface you will get the width you need with out increasing
the port volume much and with out fear of cutting into water.

You don't want to hog it out, thats a big mistake. Cut a little at a time and
measure your progress.

Print a picture of the port I posted and put it near your porting area, you can
use that as a guide. Remember I posted picture of a race port, you don't
need to remove that much material, its the shape you are after.
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Old 05-05-2010, 10:18 PM
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Thanks for the tips!
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