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Old 11-05-2012, 04:02 PM
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Intake Port Gasket matching Vortec Heads

like the title says, is it good or bad to do in a vortec head? i did it to one of my 2 pairs of l31 vortec heads before reading some info on working on vortec heads, and read that by messing around with intake ports will ruin the heads performance is this true? by the way I did the port matching and went like 1 inch deep into the intake port just cleaning up no cutting.

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Old 11-05-2012, 04:06 PM
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It doesn't hurt nor help anything.
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Old 11-05-2012, 04:11 PM
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Originally Posted by ap72 View Post
It doesn't hurt nor help anything.
so are they still good? even though i went 1 inch deep inside polishing the port?
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Old 11-05-2012, 05:00 PM
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Originally Posted by Jkingof956 View Post
so are they still good? even though i went 1 inch deep inside polishing the port?
you didn't affect anything.
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Old 11-05-2012, 05:17 PM
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I agree with AP72 that you probably haven't helped or hurt anything. Current thinking has the intake ports left rough and the exhaust ports polished, but unless I had a Doctorate in Fluid Dynamics or many years experience grinding on heads, I'd either leave 'em alone or take 'em to someone who knows what to do to them and how to do it. Also, think about what it takes to port match. You end up with a runner that looks like an Anaconda that swallowed a pig (the passage runs standard volume, then enters your increased volume section, then necks down again). Where the passage gets larger in volume, the air/fuel mixture slows down and can drop fuel out of suspension, particularly if the surface of the port is polished, resulting in puddling and a rich/lean/rich/lean condition. There is a boundary layer in any port where the surface can be as rough as a fingernail file and not hurt flow.

I generally refer to a river in order to explain this. If you stand at the bank of a river, you'll see that the major volume of flow and speed is right down the middle and that the flow is very much stalled at either bank of the river. Same way in a port, fast down the middle and slow at the surface of the port.
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Old 11-05-2012, 05:44 PM
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Originally Posted by Jkingof956 View Post
like the title says, is it good or bad to do in a vortec head? i did it to one of my 2 pairs of l31 vortec heads before reading some info on working on vortec heads, and read that by messing around with intake ports will ruin the heads performance is this true? by the way I did the port matching and went like 1 inch deep into the intake port just cleaning up no cutting.
The Vortec likes a little clean up on the intake and exhaust, nothing too radical just follow the usual practice of removing sharp edges, smoothing the guides, remove any rough blends between the seat ream and the port walls. This head really likes a 30 degree back cut on the valves themselves and is responsive to 1.6 rockers after you fix the guides for that much lift. There is not advantage to polish and don't smooth the plug boss its abrupt shape does a lot to remix the fuel stream back into the air flow. There isn't much to be gained in port matching the intake unless you're going to run the engine at the extreme upper end all the time.

Bogie
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Old 11-05-2012, 07:04 PM
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thanks guys for the info, am uploading pics so you guys can see if they are messed up or still good to go...
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Old 11-05-2012, 07:09 PM
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this is the port matching in one head:

[IMG][/IMG]

and other head port matched:


stock exhaust port:


cleaned up exhaust port:
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Old 11-05-2012, 07:11 PM
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Porting vortec heads will only gain you a couple more HP. They were made to flow as much as possible from the factory already. They did a good job making them you're not gonna improve much on what they've already done.
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Old 11-05-2012, 07:19 PM
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Porting vortec heads will only gain you a couple more HP. They were made to flow as much as possible from the factory already. They did a good job making them you're not gonna improve much on what they've already done.
i knew this already but i was just curious on cleaning up the inside casting marks not porting or reshaping
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Old 11-05-2012, 07:41 PM
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Originally Posted by BraveLil305 View Post
Porting vortec heads will only gain you a couple more HP. They were made to flow as much as possible from the factory already. They did a good job making them you're not gonna improve much on what they've already done.
A good port job can pick up 30cfm... that can be something significant to some people.
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Old 11-05-2012, 08:24 PM
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i knew this already but i was just curious on cleaning up the inside casting marks not porting or reshaping
I'm picking up what you're laying down
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Old 11-05-2012, 08:37 PM
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so guys based on the pics i posted what do you all think will it hurt what has been done?
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Old 11-05-2012, 09:09 PM
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so guys based on the pics i posted what do you all think will it hurt what has been done?
They're fine- you're worrying too much, me thinks.

In the future what you can look to remove is any "overhang" into the port that is seen as viewed from the intake into the head's intake port. You don't want any of the head's intake flange obstructing the flow from the intake manifold's port into the head. If there's a mismatch as seen looking from the head back into the intake, this can be ignored. Actually, some say this mismatch can reduce reversion in some cases.

It takes careful measurements to get this precise- to the point of mocking up the heads on the block then mounting the intake using templates (or intake gaskets) as references.

What can happen when doing a simple gasket matching of the ports, is a bulge is created where the head and intake meet. Someone here referred to it as looking like a snake that ate a rabbit, or something like that. This is to be avoided! What will happen is the flow slows as the cross section enlarges and this can cause turbulence and reduced flow.

You can do a search for port matching as opposed to gasket matching for more details.
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Old 11-06-2012, 04:53 PM
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Originally Posted by cobalt327 View Post
They're fine- you're worrying too much, me thinks.

In the future what you can look to remove is any "overhang" into the port that is seen as viewed from the intake into the head's intake port. You don't want any of the head's intake flange obstructing the flow from the intake manifold's port into the head. If there's a mismatch as seen looking from the head back into the intake, this can be ignored. Actually, some say this mismatch can reduce reversion in some cases.

It takes careful measurements to get this precise- to the point of mocking up the heads on the block then mounting the intake using templates (or intake gaskets) as references.

What can happen when doing a simple gasket matching of the ports, is a bulge is created where the head and intake meet. Someone here referred to it as looking like a snake that ate a rabbit, or something like that. This is to be avoided! What will happen is the flow slows as the cross section enlarges and this can cause turbulence and reduced flow.

You can do a search for port matching as opposed to gasket matching for more details.
so now that I messed up on port maching with gasket am I now am forced to gasket matched my intake manifold???
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