Intake Manifold Porting Show ‘n Tell

[Bigchief632]

Holley Strip Dominator 300-25 in progress...

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Quick question Scott although probably covered before: When doing a gasket match like that are you using the bolt holes as "dowels" or do you go so far as to actually pin the manifold flange.?

"Port matching" intakes is usually done wrong. Most guys slap the gasket on, scribe it out, and grind to the lines. 8 of 10 times, the width at the outlet is wider than the minimum width at the pushrod pinch. Even after doing extensive rework in that area. You're reducing performance usually.

Head is an M2 CNC Brodix track 1 I am repairing. See weld. Intake is the Holley 300-110 OTB

[skinny z]

"Port matching" intakes is usually done wrong. Most guys slap the gasket on, scribe it out, and grind to the lines. 8 of 10 times, the width at the outlet is wider than the minimum width at the pushrod pinch. Even after doing extensive rework in that area. You're reducing performance usually.

You kind of lost me there.
Case in point. The heads I have look to have an application suitable MCSA at the pushrod pinch. 2" x 1". This is less than an inch in from the mating flange.
The opening at the head flange is certainly larger in area in both dimensions. Opening that to match the gasket makes it larger still.
One reason for matching the gasket on the head is because it's a fairly good fit on the manifold already and the port on the head hangs inside obviously obstructing flow (or at least I would think it is).
So what do you there?
Digging into pushrod pinch is not an option at this time.

[mt-engines]

"Port matching" intakes is usually done wrong. Most guys slap the gasket on, scribe it out, and grind to the lines. 8 of 10 times, the width at the outlet is wider than the minimum width at the pushrod pinch. Even after doing extensive rework in that area. You're reducing performance usually.

You kind of lost me there.
Case in point. The heads I have look to have an application suitable MCSA at the pushrod pinch. 2" x 1". This is less than an inch in from the mating flange.
The opening at the head flange is certainly larger in area in both dimensions. Opening that to match the gasket makes it larger still.
One reason for matching the gasket on the head is because it's a fairly good fit on the manifold already and the port on the head hangs inside obviously obstructing flow (or at least I would think it is).
So what do you there?
Digging into pushrod pinch is not an option at this time.

If the pinch is the smallest point.. making it YUUUUGE upstream is a waste of time and won't gain anything.

I normally will blend the pinch back to whatever the flange area is. And square it to look nice. I won't carve it out to 1.310 if the pinch is .850 or even 1.200. Its a waste of time.. and does nothing.. most times the intake manifold gets some plenum blending and some work a inch from the flange . But rarely does it get the gasket width.

[ChopperScott]

Quick question Scott although probably covered before: When doing a gasket match like that are you using the bolt holes as "dowels" or do you go so far as to actually pin the manifold flange.?

I’m not using the drill and pin method. I have the AFR 220 CNC ported heads on my old 355 block for reference to prep multiple manifolds.
- I tape a 6901 gasket to the head with black masking tape, and install the manifold with 4 bolts snug.
- Check port alignment through runners, then remove tape from the head and transfer to manifold. Remove manifold with gasket and scribe reference points.
- Repeat with a 1206.
- Mark lines with a square on machined surface.
- Use 6901 to mark radius in the corners

A 6901 is taller than a 1206. I’m shaping the ports on the manifold to match the AFR head, but still be able to fit a 1206 port. I’m also using an inside caliper during the process to maintain port size and shape. I’ll recheck alignment and final finish after all 8 ports are close.

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This is how AFR CNC matches the ports on the Eliminator manifold…

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[Bigchief632]

"Port matching" intakes is usually done wrong. Most guys slap the gasket on, scribe it out, and grind to the lines. 8 of 10 times, the width at the outlet is wider than the minimum width at the pushrod pinch. Even after doing extensive rework in that area. You're reducing performance usually.

You kind of lost me there.
Case in point. The heads I have look to have an application suitable MCSA at the pushrod pinch. 2" x 1". This is less than an inch in from the mating flange.
The opening at the head flange is certainly larger in area in both dimensions. Opening that to match the gasket makes it larger still.
One reason for matching the gasket on the head is because it's a fairly good fit on the manifold already and the port on the head hangs inside obviously obstructing flow (or at least I would think it is).
So what do you there?
Digging into pushrod pinch is not an option at this time.

The inside divider is showing the narrowest point inside the intake port of the head. Then, I'm showing you how wide the untouched manifold is at the exit using that dimension compared to the head. If you scribed the gasket out, or even close, and then started hogging away, the outlet at the manifold would be an easy 1/8 wider than the minimum point at the pushrod pinch. It's wrong in my opinion to do that. It's really not an opinion really. Follow?

[skinny z]

"Port matching" intakes is usually done wrong. Most guys slap the gasket on, scribe it out, and grind to the lines. 8 of 10 times, the width at the outlet is wider than the minimum width at the pushrod pinch. Even after doing extensive rework in that area. You're reducing performance usually.

You kind of lost me there.
Case in point. The heads I have look to have an application suitable MCSA at the pushrod pinch. 2" x 1". This is less than an inch in from the mating flange.
The opening at the head flange is certainly larger in area in both dimensions. Opening that to match the gasket makes it larger still.
One reason for matching the gasket on the head is because it's a fairly good fit on the manifold already and the port on the head hangs inside obviously obstructing flow (or at least I would think it is).
So what do you there?
Digging into pushrod pinch is not an option at this time.

The inside divider is showing the narrowest point inside the intake port of the head. Then, I'm showing you how wide the untouched manifold is at the exit using that dimension compared to the head. If you scribed the gasket out, or even close, and then started hogging away, the outlet at the manifold would be an easy 1/8 wider than the minimum point at the pushrod pinch. It's wrong in my opinion to do that. It's really not an opinion really. Follow?

I do now. (I'd missed that one picture was of the manifold). Thanks.

That said, and a question I've asked before (but I don't recall to who), what's your (or any contributors) take on the port opening being smaller than the manifold? One reply quoted Joe Sherman and his view on oval port heads to square port manifold. Joe said it didn't make a difference but the evidence points to that being an outlier.
I'd think it be worth some effort to at least even them up.
Or is this a non-issue?

[Tom68]

I'd think it be worth some effort to at least even them up.
Or is this a non-issue?

The old "it depends" would apply, matching them at least makes them right, but a big manifold runner stepping to a small port would take dyno testing against blend/matched to know, a flow bench would probably show improvement with a long blended match for the different sizes.
If the head port and manifold port have similar csa's either side of the gasket for a couple of inches you'd think matching would be important.

But yer it'd be nice to see some actual testing.

[Tom68]

To add to matching, we don't all get to throw perfect combos together hence the potential to have large variances in CSA's between head and manifold runners, if you're running a low dual plane on some decent heads the lower runners will be very small, the upper runners may have some size but then the floor will be too close to the carby anyways.

The Old Edelbrock C3BX and some Weiands seem to try and address the port size by using width, I'm not familiar with newer ones but there are some shockers despite some of those performing reasonably well.

Single planes are whole nother ball game, at least with siamese ports on a SBC we get some length in the center runners.

[skinny z]

I'd think it be worth some effort to at least even them up.
Or is this a non-issue?

The old "it depends" would apply, matching them at least makes them right, but a big manifold runner stepping to a small port would take dyno testing against blend/matched to know, a flow bench would probably show improvement with a long blended match for the different sizes.
If the head port and manifold port have similar csa's either side of the gasket for a couple of inches you'd think matching would be important.

But yer it'd be nice to see some actual testing.

Something about the air and fuel arriving at an abrupt edge somehow to me doesn't seem conducive to good flow.
But again, as you say, testing would tell the tale.
I'll have to get in there with an inspection camera as it's a dual plane with no line of sight or some means of transfer to get a proper determination on how much of a mismatch there is. The old gaskets still stuck to the heads in some places and to the manifold in others might prove useful.

[Tom68]

Something about the air and fuel arriving at an abrupt edge somehow to me doesn't seem conducive to good flow.

Bad for the air, maybe good for the fuel stuck to the walls from going around 90 degree corners.

[Tom68]

Something about the air and fuel arriving at an abrupt edge somehow to me doesn't seem conducive to good flow.

Bad for the air, maybe good for the fuel slowly flowing along the walls after going around 90 degree corners.

[1980RS]

I am still a believer in what Joe Sherman said years ago, that "port matching is a waste of time". In 2019 I ran my GM super victor Vortec intake but the ports were so bad on it I had to open them up to a 1206 gasket from the Vortec pattern. When I decided to run that on my flat top 406 with my 062 2nd Vortec head test, the side walls and port roof were horribly off, but I ran it anyway. Didn't seem to matter, the car ran like a scalded cat and I blasted down the track into the high tens. Never in a million years would I have ever though that something that badly matched would go that well. Reminds me again of the Square port intake on oval port heads, still seems to work.

[Bigchief632]

I am still a believer in what Joe Sherman said years ago, that "port matching is a waste of time". In 2019 I ran my GM super victor Vortec intake but the ports were so bad on it I had to open them up to a 1206 gasket from the Vortec pattern. When I decided to run that on my flat top 406 with my 062 2nd Vortec head test, the side walls and port roof were horribly off, but I ran it anyway. Didn't seem to matter, the car ran like a scalded cat and I blasted down the track into the high tens. Never in a million years would I have ever though that something that badly matched would go that well. Reminds me again of the Square port intake on oval port heads, still seems to work.

The reason port matching is a waste of time, is because in many cases, the manifold is already bigger than the head. See picture above. It doesn't look trick, and shiny, and fast like Scott's pictures above, but I would bet the intake is much wider at the outlet than the narrowest point in the head he has pictured. There's no pushrod pinch in the intake, measuring the cross section is much easier, and if it has more area , then adding more, is a negative, and or, won't gain anything. Squaring them up, and making them even, is good, using the gasket as a template, and "matching" them isn't what you want.

[skinny z]

I am still a believer in what Joe Sherman said years ago, that "port matching is a waste of time". In 2019 I ran my GM super victor Vortec intake but the ports were so bad on it I had to open them up to a 1206 gasket from the Vortec pattern. When I decided to run that on my flat top 406 with my 062 2nd Vortec head test, the side walls and port roof were horribly off, but I ran it anyway. Didn't seem to matter, the car ran like a scalded cat and I blasted down the track into the high tens. Never in a million years would I have ever though that something that badly matched would go that well. Reminds me again of the Square port intake on oval port heads, still seems to work.

A 1206 manifold opening to a Vortec port? That's about as far off as I could imagine.
Looking at the RHS port and the Edelbrock 7516 intake, it's night and day compared to the mismatch above. In fact I'd say it's pretty good judging by the imprints on the gasket.
It may be that aside from a little trimming of the gasket that's edging into the port in various locations, that this will go back together just as it came apart.

[Monza355]

I am still a believer in what Joe Sherman said years ago, that "port matching is a waste of time". In 2019 I ran my GM super victor Vortec intake but the ports were so bad on it I had to open them up to a 1206 gasket from the Vortec pattern. When I decided to run that on my flat top 406 with my 062 2nd Vortec head test, the side walls and port roof were horribly off, but I ran it anyway. Didn't seem to matter, the car ran like a scalded cat and I blasted down the track into the high tens. Never in a million years would I have ever though that something that badly matched would go that well. Reminds me again of the Square port intake on oval port heads, still seems to work.

Joe Sherman also said the Intake Manifold was just there to hold the carburetor