speedtigger

iTrader: (16)

Recently, I tested a new intake manifold compared to my old one. The Victor Jr. was a faster on my combo than the Old Performer RPM. Now that I decided to keep the Victor Jr., it is time to port match the intake to the PRC CNC ported LS6 heads. I am excited to see if even more power gains are possible.

I thought it might be nice to share pictures of the process I use to perform port alignment and port match between the heads and the manifold.

Here is a picture of the intake on the motor ready to begin the process:

speedtigger

iTrader: (16)

One of the things that I learned from port matching my Performer RPM manifold to the PRC heads is that the port entry size on the PRC CNC 243 heads is so large that you cannot get a true port match while retaining the factory O-ring gaskets. So, it is necessary to fill in the the gasket o-ring receiver grooves with epoxy on the Edelbrock manifold and then use the Mr. Gasket paper gasket.

The next thing that I learned is that the port alignment on the Edelbrock manifolds is pretty far off. This situation assures that you cannot use the o-rings when pursuing a good port match with the PRC CNC heads. Notice how the scribe of the intake port goes right into the o-ring gasket receiver groove.



Now that we have covered those obstacles, lets get started with the port alignment and matching process.

parks450

iTrader: (17)

wow that is pretty far off, is that due to the prc heads or maybe a slight casting flaw in the intake? perhaps both?

speedtigger

iTrader: (16)

Before I get ahead of myself, I want to share my process for manifold alignment and port alignment. The challenge is to get the ports to line up perfectly and transfer the size and shape of the larger port to the smaller port for a perfect match. This is not easy because once the manifold is on the car, you can't see if it is lined up and have no access to the mating surface to scribe it for modification.

On old school motors like small block Chevy, the standard process is to just port match both the head and the intake to a popular sized gasket. On the PRC CNC ported 243s, they do not appear to be ported to any gasket size I am aware of, so a custom match is necessary.

Since there is no gasket to match to, we need to make a template from cardboard. So, here we go:



As you can see, I am using a blue manila folder for a template. In the picture you can see I am using a small-ball peen hammer to tap around the edge of the port. This cuts the paper in the perfect shape of the cylinder heads intake port.(this tip was from Mike at T. E. A.). It is important that the cardboard is secure so that the template does not move during the process which could cause you to lose alignment.

speedtigger

iTrader: (16)

Here I am removing the paper covering the port after peening the edges to cut the paper as described previously:

speedtigger

iTrader: (16)

A little further along:

speedtigger

iTrader: (16)

All the ports cut:

dopy

Thanks for the Info so far.

speedtigger

iTrader: (16)

Here, the intake is back on the motor. One nice advantage of match porting the victor jr is that you can see the alignment of the center 4 ports by looking into the intake through the carb pad.



If you do not have this luxury, you can use a socket. Simply find a socket that is just large enough not to fall into the cylinder head intake ports. Lay that socket in the intake port of the cylinder head sideways, then set the intake on top. The shape of the round socket will let the intake set down on the heads, but it will center the intake. If the socket is the right diameter the intake will go on but will not slide forward or back. If it does still slide forward or back, use a larger diameter socket. If the intake will not set down on the head flush, try a smaller diameter socket.

speedtigger

iTrader: (16)

Once the intake is optimally centered front to rear, scribe the outside of the intake perimeter with a pencil onto the template. This will serve as a double check later:

speedtigger

iTrader: (16)

I forgot to mention to put the intake bolts in and snug them up. This makes sure the intake is fully seated so that the vertical port alignment will be correct when the intake is finish installed.

Now that the intake is snugged up, i drill two 1/8" holes on each side through the intake flange, through the template and slightly into the head. This will provide us a hole in both the head and the intake for an 1/8" guide pin for perfect alignment. This will allow for perfect transfer of port size, shape and alignment from the head to the intake via the template.

speedtigger

iTrader: (16)

Once the guide pin holes are drilled, vacuum up the metal from the drilling process before removing the intake. Once the metal is cleaned up, I remove the intake and put it on the bench. Next I take the template and lay it on the manifold centering it and securing it with two 1/8" guide pins. In the photo you can see I use two 1/8" arbor dremel bits as makeshift guide pins:



Make sure you label the templates drivers side and passenger side.

speedtigger

iTrader: (16)

Here is a close up shot. We can see how much larger the CNC ports are than the stock Victor Jr. ports:

speedtigger

iTrader: (16)

Notice how off center this particular port is compared the port in the previous photo. Mike at T. E. A. told me I would run into this with this intake. He was right.



If you notice, the upper left hand corner of this port is right on the edge of the o-ring receiver groove:

speedtigger

iTrader: (16)

The next thing that is needed is to paint the intake manifold gasket surface so it can be scribed from the template. The proper product to use for this is machinist die. However, I don't have access to that today, so I will use fast dry paint for demonstration purposes. The down side with using paint is that it will not hold up to exposure to the oil that is used to lubricate and cool the die grinder bit used in the porting/grinding process.



Now to scribe the paint:



And the finish scribed port ready for grinding. As you can see, the port location will go right into the reciever groove for the o-ring gasket. So, the o-ring receiver grove will have to be filled in with epoxy and let cure before the porting/grinding begins:

speedtigger

iTrader: (16)

One last thing that needs to be done is some light grinding in the carburetor flange/plenum area. Notice that the spacer & gasket do not line up leaving an exposed sharp edge under the carburetor which could be a source of unwanted turbulence:

speedtigger

iTrader: (16)

One of the key elements that must be noted in intake manifold port matching is that just opening up the area of the port at the gasket like a funnel is not optimal. The ideal arrangement is to have either a uniform port cross sectional area from end to end or a slight taper down. So, some measurements must be taken to assure that this can be accomplished. We are looking to see the port is larger in cross sectional area in the plenum than the cross sectional area we hope to open the port to at the head. On many high performance manifolds, the port tapers from larger to smaller. This allows a porter to accomplish this fairly easily. However, many others like the Performer RPM do not have taper. In these cases opening up just the area at the cylinder head side of the intake port may have little to no performance benefit and some chance of detriment.

speedtigger

iTrader: (16)

What I found in measuring is that the port openings in the plenum were approx 2.825" x 1.10". So 3.10" square inches cross sectional area.

At the cylinder head, the Victor Jr. factory port size is 2.70" x 1.0". So 2.7 square inches.

This means the Victor Jr. is designed with the port taper we were hoping to find. However, we need to compare the plenum area port opening to the size port that we hope to open to. We hope to open the intake port to 2.70" x 1.150" or 3.10 square inches. Lucky? Yeah, I would say so.

Now that we know the intake manifold design can be ported to the size we need. All that is left is some hours of careful measuring, grinding and porting and blending.

Stay tuned for track testing to see the actual net performance gains.

The last trip to the track produced a 7.28 @ 95.6 MPH in -100 d/a with a 15 mph headwind. I am excited to see the results.

mbaker3

What epoxy are you using?

Paul57

This is great timing. I was going to start my intake tonight.
How did you know you weren't drilling into the water jacket??
Did TEA do your RPM too??
What is the part number of the gasket that is needed??
Any chance you want to sell your RPM intake?? I just bought PRC Stage 1's.