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Old 11-05-2009, 01:35 PM
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porting intake manifold?

Hey guys is there such thing as porting your intake manifold such as the same way the heads are being done nowadays? I have a set of AFR eliminator aluminum heads fully ported and polished along with an edelbrock performer rpm air gap manifold that is "as cast" in the plenum. It has a very rough finish to it in the runners, I would assume it would be a good idea to port your intake manifold and smooth out the runners if your heads has port and polished runners. I can't see only having the head runners port and polished would make much of a difference unless the intake manifold was done the same way? Would a machine shop be able to port the intake manifold? Suggestions?

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Old 11-05-2009, 01:39 PM
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For a dual plane manifold you may want to look into extrude honing.
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Old 11-05-2009, 04:30 PM
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Like AP hinted at, a dual plane is virtually impossible to port like the head because you can't reach every inch of the port with your grinding tools. This type of porting is usually only viable on a single plane manifold. The only ways to port a dual plane are to cut access holes in various places, do the port work, then weld the access holes back up and finish them off, or send it out to be extrude honed.

Extrude Honing is where they pump a grit filled mud-like substrate through the manifold under high pressure, the grit in the mud cuts away at the most restrictive points in the manifold and polishes everything. It's $$$.

You are correct in that a small intake port will hold back the heads potential. If you are that worried about power, you should be running a single plane anyway, as it will be high rpm power that is hurt by a too small intake. Low end will be virtually unchanged.
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Old 11-05-2009, 06:29 PM
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All things considered, you don`t want to polish the runners. Leaving them rough causes the air/fuel mixture to tumble that aides atomization which is important in helping combustion. This is especially important when using nitrous oxide. And it`s equally important if the engine has a poor quench distance.
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Old 11-05-2009, 07:48 PM
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As mentioned smooth intake runners promote fuel separation and are not desirable. The only porting work I would do on a performance intake would be to port match the runners to the heads and that's it.

Vince
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Old 11-05-2009, 10:54 PM
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Ok so to port match the runners to the head what would be involved? Is this something that one can do themselves at home or does the intake and heads have to bet sent to a machine shop? I can tell just by comparing the ports on the intake and the ports on the head that they are not the same. The ports on the head look larger (because the runners have been ported) and the ports on the intake manifold dont even all match in size themselves! I think edelbrock stuff is being made in China now.
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Old 11-05-2009, 11:27 PM
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basic procedure for that is to make a template that matches the ports and then register the template to the manifold..once that is done then scribe around the port on the manifold and then get to work with the die grinder on the manifold..If you have a long nose die grinder you can get quite a ways up the mainifold runner and do not worry too much as some roughness will help as previously discussed..We made our templates from scrap pieces of formica as that seemed to work well..

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Old 11-06-2009, 06:53 AM
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It's fairly common to use an intake gasket identical to the one that will ultimately be used to do the final assembly of the engine with. When the gasket is placed onto the blued intake flange of the head and intake, a mark indicating the port opening is scribed.

The only "trick" to this, is to be sure that the intake gasket is aligned the same on the head as it is on the intake. Because the intake manifold and intake gasket's bolt holes are larger than the bolt itself, care must be used.

Taper the port as gradually as you can. This will depend on how long the tooling is that's being used. I'd shoot for at least 2", if possible.

You can secure the gasket using a few short bolts w/flat washers. Center the gasket holes to the head's holes; same thing w/the intake manifold, except the bolts need to have nuts.

Sometimes, bolting the intake to the heads will leave a gasket imprint, but the problem here is duplicating the exact position of the gasket. In this case it will be necessary to glue the gaskets in place.

What you don't want is a big "bulge" right at the gasket. Too much cross section here could cause turbulence that could undo all your work.
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Old 11-06-2009, 11:21 AM
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Quote:
Originally Posted by sexypizzaman
Hey guys is there such thing as porting your intake manifold such as the same way the heads are being done nowadays? I have a set of AFR eliminator aluminum heads fully ported and polished along with an edelbrock performer rpm air gap manifold that is "as cast" in the plenum. It has a very rough finish to it in the runners, I would assume it would be a good idea to port your intake manifold and smooth out the runners if your heads has port and polished runners. I can't see only having the head runners port and polished would make much of a difference unless the intake manifold was done the same way? Would a machine shop be able to port the intake manifold? Suggestions?
The only way to work inside a 180 degree manifold is to cut holes into it that allow a die grinder access. Once complete, the access holes are closed with soft plugs.

Manifolds are tricky to port and get effective results. The twists and turns really throw the flow all around and you get a lot of unexpected results. This is best done using a salvage manifold of the type you're planning to use on the engine with the head your planning on using and all this on a flow bench. It is a lot easier to screw a manifold up than head ports. But done right, there is a lot of flow to be had here. To a great extent, we hot rodders tend to overwork our heads to a place where the intake manifold has no possibility of coming close to feeding the head port the amount of flow it can use, so the manifold is really the pacing element to getting more flow into the cylinders. In simple terms it doesn't matter if the port can flow 200 plus cfm if the intake runner can only deliver 150 cfm, so your thoughts are in the correct place, but this isn't a simple thing to work out. Something to start considering is that the lower plane of a 180 degree intake flows about 20% less CFM than the passages of the upper plane. Also, generally, the passages on the ends supplying cylinders 1-2 and 7-8 on a Chevy are the lowest flowing passages for the plane they are on.

As these things go, the Performer RPM is a pretty good manifold. The problem it has for a street machine is common to all unheated manifolds in that it's so cold it tends to get a lot of fuel separation from the air flow. The only solution available is to keep the RPMs up so the flow velocity picks up the fuel condensing on the floor and walls. To this end you don't want smooth passages as the roughness of the casting promotes enough turbulence to throw the fuel back into the faster flowing streamlines.

I'm rather out on the usefulness of port matching unless this is an out and out competition engine and you're spending the effort at assembly to insure the ports and passages match with no more roughness than that created by the in plane seams of the manifold, gasket, and head surfaces at the joint. The slightest mismatch, where a piece of gasket or a head side port wall sticks into the streaming flow will cause all sorts of difficulty to that flow. If you must err, and often you must, it is less disruptive to have a head port and gasket outside the line formed by the intake runner. The disruption to flow tripping from a smaller to a larger edge is much less than that of a flow on a large edge approaching and having to move inward for a smaller edge.

Bogie
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Old 11-06-2009, 09:15 PM
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Thanks for all the info guys. I will go ahead and port match the intake manifold to the heads because the manifold's ports are as much as 0.200" smaller in some places!! My next question now would be regarding the appropriate intake gasket. The port size of my intake runners on the head measure approx. 2.10" high by 1.25" wide. Would I want a gasket slightly larger than this since it will crush once torqued and "swell" out a bit protruding into the port? I also remember hearing that you need a special intake gasket if using aluminum heads with an aluminum intake. Any info on this stuff is appreciated!
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Old 11-06-2009, 10:21 PM
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Quote:
Originally Posted by sexypizzaman
Hey guys is there such thing as porting your intake manifold such as the same way the heads are being done nowadays? I have a set of AFR eliminator aluminum heads fully ported and polished along with an edelbrock performer rpm air gap manifold that is "as cast" in the plenum. It has a very rough finish to it in the runners, I would assume it would be a good idea to port your intake manifold and smooth out the runners if your heads has port and polished runners. I can't see only having the head runners port and polished would make much of a difference unless the intake manifold was done the same way? Would a machine shop be able to port the intake manifold? Suggestions?
The best thing to do is port match your intake to your heads.
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Old 11-06-2009, 10:26 PM
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haha i guess im too late
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