You have to start somewhere if you want to learn something. That goes for pretty much anything in life, and starting out tackling small jobs can provide helpful experience and instill confidence as you proceed to larger jobs. Performing basic port matching of induction components is a good way to introduce yourself to the world of porting. It also gives you an excuse to buy a few new tools and it will save you a bit of money when performing the work yourself.

As we always hope is the case, but rarely is, different components don’t always work with other components when it comes to using aftermarket parts on your vehicle. There are a number of reasons for this, including a wide range of manufacturing tolerances by the OEMs, different tolerances between aftermarket companies, changes that occur over time in the casts used to make the parts, and more. Thankfully, the differences aren’t usually too difficult to overcome.

If you’ve ever torn an engine down, you’ve likely seen casting differences between the OE induction parts (cylinder heads and intake manifolds) on a stock engine. Since we’re all about improving performance, we want to optimize any combination of parts and this can be accomplished by making sure that the port sizes on two adjoining components, like cylinder heads and intake manifolds, are the same size so as not to reduce or disrupt airflow through the port. You may also find that the physical ports do line up, but maybe the gasket between them does not. You can modify that to optimize flow as well.

If you do find differences in port size, or obstructions that you would like to remove, the tools needed to remedy these situations are not expensive. We picked up a simple, yet comfortable, straight die grinder from Summit Racing Equipment for a little over $68—you’ll find a myriad of uses for a die grinder in your home garage so it’s money well spent. To do the cutting, we ordered a four-piece carbide cutting kit for $65, as well as a stick of grinding wax for $10 and a cartridge roll porting kit for $40. One other thing you’ll want if you don’t already have it is a quality air blow gun with a long barrel on it ($9.25). Depending on what you are working on, you may need the added reach the long barrel provides, and the more focused blast of air will make it easier to get all of the metal shavings out. So we’re in for under $200 on our porting supplies, and you’d likely be spending much more than that to pay someone to do the work for you.

Sounds good to us.

There isn’t a whole lot to getting a pair of ports to match up, really. You can start with the gasket as a guide, but more often than not, you’ll find that one of the castings is a bit larger, so start with the largest port and match everything to that. Port matching isn’t the same as porting a cylinder head or an intake manifold runner, which is a job that shouldn’t be taken lightly. That sort of porting requires additional research with regard to the available material in the castings you are working with, as well as an understanding of airflow and fluid dynamics. Changing the physical design of an intake runner can have both good and bad implications on performance. That is beyond the scope of this article, though, as we just want to clean the edges up and make sure that the parts are all fitting nicely together without creating any unnecessary turbulence or restrictions to the airflow.

That said, we’ve been in the process of assembling an updated, Tuned Port Injection-based engine for a third-generation F-body. The first step to optimizing a TPI setup, even a stock one, is to clean up the inside of the upper plenum. Tuned Port Injection systems are well known for creating great torque thanks to their long-runner design, but this comes at the cost of upper rpm horsepower—most TPI engines are all done by 4,800 rpm or so. While there are larger aftermarket runners and lower intake manifolds available, no one makes a larger upper plenum and that becomes the biggest restriction. Optimizing it is thus essential for the application. In the photos below, you’ll see how we opened up the upper plenum to match the larger openings of the aftermarket throttle body we are using, as well as the larger intake manifold runners.

Here are a couple of tips before you get started with your port-matching adventure. First, the metal that comes off is going to go everywhere, so wear some sort of leather footwear unless you are sure that the metal filings will not reach your feet. Said filings are a royal pain in the behind if you’re trying to extract them from porous and intricately designed sneakers. Second, long sleeves are a good idea, though the air blower gun does a good job at removing the metal filings from your arms. It goes without saying that eye protection is a must—you only have one set of eyes so take care of them! When it comes to performing the work itself, always be mindful of the thickness of the material you are working with, and be sure to use Tap-Ease or some other bit wax to keep your equipment clean.

Happy porting!

grinding tool with carbide bits and air gun
throttle blade inside a throttle body port mouth
close up of a port on a manifold gasket
throttle body with gasket applied to mark where porting should occur
applying grinding compound to a grinding tip
close up of mating service on a tpi intake plenum
close up of port machining work done on an intake
man testing smoothness of an intake port using his finger
porting work done on an intake manifold
magic marker used to show where to grind a port
tpi intake plenum mouth
tpi throttle body

You don’t have to spend a lot of money to get what you need to do basic port-matching. A few key tools and a couple that make your life easier while performing this task is all it takes.

Upon bolting on a new throttle body to our classic Tuned Port Injection engine, we found there to be a large difference in size between the new throttle body and the factory upper plenum. Since the goal of bolting on larger intake components is to increase the amount of air going into the engine, it only makes sense to open up the plenum to match the throttle body. Otherwise the sharp edge will inhibit flow and create turbulence.

On the sides of the plenum, we have a similar issue with the oversized intake runners being a larger diameter than the factory ones. This isn’t as much of a problem as the throttle body, as you’re going from a smaller port to a larger one, but gains in airflow can be had by opening up the factory plenum to match the size of the gasket that was included with the larger runners. You’ll want to verify that the gasket isn’t restricting the runners as well here.

Turning our attention back to the throttle body, we’ve mocked up the gasket that came with it and used a Sharpie to mark the plenum face. As you can see, there is quite a bit of material here to remove. Be sure to verify that the plenum, or whatever you are porting, has enough material on the backside so that you don’t break into a water jacket or the outside of the piece.

We can’t recommend using Tap-Ease or a similar substance enough when porting. It prevents the millings from clogging up the bit and keeps them cutting like they should. This is especially important when porting aluminum, as the softer metal likes to melt into the cutting surfaces of the bit.

One thing to note about TPI plenums (some, not all) are the small walls that are just inside the throttle body opening. In this picture, you can see the wall on the left side, and that it has been removed on the right side. They are not so much of a nuisance with a stock throttle body, but taking them out is essential when you’re opening the front for a larger throttle body.

Here you can see that the inner wall has been removed and we are giving the entire surface inside a clean-up. If you find that there is a corner that you can’t seem to get to, like the one in the bottom right to the back of the throttle body opening, just leave it alone. It’s not worth going after it when the risk that you’ll break through to the other side is greater, and it’s likely already larger than the rest of the port anyway. Being mindful of what is on the other side of the metal you are working will keep you from making decisions that could trash an expensive part or require a professional to repair.

Just because it looks flat and smooth doesn’t mean that it is. Use your fingers to feel the subtle changes in the surface and you’ll likely find that there is more work to be done.

When you’re porting, it’s very possible that you will encounter casting flaws. Here you can see that there was some air trapped in the casting of the plenum on the right side. Again, it’s better to leave such things alone, especially when it’s so miniscule in size. If it’s a bigger issue, you can always epoxy it or weld in some additional aluminum and then finish your porting.

In this photo, you can see how rough the carbide bit has left the surface on the left side. The right side has seen two grit changes with the cartridge rolls to further smooth out the surface. You can get really carried away and polish the innards to a mirror-like finish, but we’re just mostly removing obstructions in this case and cleaning things up.

With both sides of the throttle body opening ported and rough-polished, our TPI upper plenum is looking quite spiffy. You can see how thin the plenum gets in the center, and it is pretty thin on the backside of the mounting flange in the corners as well, so keep your eye on those areas when removing material.

With the new throttle body mounted up and opened, you can see that the big shelf that once was there is now just a smooth transition into the upper plenum. The walls on the floor of the plenum are also gone and now the intake charge is free to zoom in and take advantage of your larger induction components.


Author: Steve Baur

Steve Baur is the founder and principal of Driven Media Works, a Florida-based creative-services firm serving the automotive aftermarket. After attending the University of South Florida for journalism, Steve signed on with Muscle Mustangs & Fast Fords magazine, where he served as associate editor and, later, technical editor during his nine-year tenure. In 2010, he was promoted to the editorship of Modified Mustangs & Fords, a publication he helmed for four years before launching Driven Media Works in 2014. A lover of all things automotive, Steve has contributed to a wide range of motoring publications, including Car Craft, Truckin', Modified, Super Chevy, Race Pages, GM High Tech Performance, Fastest Street Car, and High Performance Pontiac.