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How to polish the interior of an intake manifold
First, remove the intake manifold from the vehicle so you can readily reach all intake parts.We suggest starting with a product called Purple Power, or something very similar. You'll want at least the following:
- Purple power, or an automotive metal cleaner
- A long bristle brush that can reach into the manifold
- Rubber gloves
- Optional: an automotive snake camera to see the before and after
- A place you don't mind getting dirty
Polishing the inside of an intake manifold is fairly easy, assuming you have the ability to take the intake manifold out. While there are different metal types for an intake manifold, from plastic to aluminum, or cast iron, Purple Power still works. You will want to be careful with Purple Power though. It can cause oxidization and corrosion if you let it soak. We will discuss the important steps to using Purple Power below.
Getting started: Pour Purple Power In
Pour purple power into the intake manifold. You should also be sure to follow the instructions on your specific bottle and for your vehicle in case it calls for dilution – or adding water to lessen the strength of the cleaner.
Start working with the long bristle brush right away to avoid having the purple power sit too long. Push the bristle brush into the intake manifold and “scrub” it back and forth to start loosening and removing carbon. While it is not especially easy to see just how clean your intake manifold is getting on the inside while there is Purple Power, water, and junk in there – if you see a steady flow or black and brown debris swimming out, you are probably doing something!
Do this to every port on your intake manifold until you are done. Doesn't matter what order as they are all the same.
Once you have completed the process for all your ports, thoroughly rinse the ports out with water and allow the manifold to dry. The purpose of rinsing is both to get extra junk out of the manifold, and because Purple Power has the potential to degrade any gaskets and aluminum if let to sit for too long.
While you don't 'need' to do this by any means and it is probably not worth it if you don't already have one – but some automotive enthusiasts have a scope camera on a long wire they can push into the manifold. This will give you a good idea of where most of the carbonized junk is, and know the current state of the manifold. Doing a before and after photo scan is a good idea to show just how much stuff was removed and find any other potential problems like corrosion.
Why would I polish the intake manifolds inside?
There is a chance you'll increase engine performance. Why? Intake manifolds are precision built to bring in the right amount of outside air into your vehicle so that it can combine the oxygen with gasoline for combustion. Carbonized (hardened due to heat) fuel, debris, and many other things have the potential to get stuck in your intake and make it difficult for air to flow freely. An engine, and especially a higher performance engine, needs all the air it can get to function at a high level.
While this article won't cover the process in much detail, you can also “Port” your manifold by cutting slightly larger holes with a grinder or drill and attachment. These allow for more air to flow in, and potentially faster, and are much more of a modification than simply polishing the interior with a brush.
Aside from the more difficult process of “porting” your intake manifold, polishing does have something to offer for performance.
How to polish intake manifold outside
We'll be a little honest about the idea of polishing the exterior of your intake manifold. There aren't many performance advantages associated with this particular project. However, if you do like to bring your vehicle to car shows or otherwise like a spotless engine, it is a good idea to make it look clean and original.
Just like cleaning the interior of the intake manifold, the exterior is often even messier though a much different process. Since your intake manifold sits in your engine, it is likely coated in dried grease, a few layers or dust, dirt, and whatever else might pop up from the undercarriage. Unless you have a ceramic coated intake manifold or some way or protecting it, the intake manifold probably looks a bit darker than when you first bought it.
With all of that said, you'll need:
- A (preferably) air powered grinder with compressor
- Sanding and polishing pads for the grinder with a range of tough to fine grits
- A respirator
- Ear protection
- Work gloves
- Safety glasses
- A liquid polishes for the end
Start out by removing the intake manifold from your vehicle. Since this involves work and time you might want to clean the exterior of the manifold before the interior while you still have it out.
Get your air compressor setup with your air grinder and a sand disk tough enough (we might suggest 180+ but it depends on how bad the manifold is) to cut through the first bad layer of junk. The manifold exterior is very tough and has survived high temperatures since manufactured and probably won't be harmed by grinding.
The first step is to put on your safety glasses, ear protection, and gloves. There will be pieces of dust and carbonized who knows what actively flying off your intake manifold, and your eyes and ears are not places you want these bits to go.
Turn on the air grinder and begin grinding away at the worst parts of the exterior. Another option here is to use a rotary tool with sanding bits. Try to angle and move your grinder to reach every inch possible, including the use of different disks that fit better into unique locations. Your other option here is to hand parts of the intake manifold by hand, which of course will take longer.
You can move on to a lighter grit after one pass, and potentially clean up with the first pass- and yourself. The idea is to use a lighter grit to make the first pass move smooth while cleaning up anything left. Note that you can move in the opposite direction and put a tougher grit on if the first pass didn't work as well as you hoped.
Repeat this process going with a lighter and lighter grit.
How should my intake manifold look after being polished and sanded?
We previously discussed going with lighter and lighter sandpaper or polisher grits because the idea is to get the intake as shiny as possible. Lower grits allow for a very even surface that provides a mirror like finish.
The next step after sanding is to use compounds and actual polishes that protect the intake manifold and make them look extra reflective and shiny, if that is what you are going for. These can be applied by hand or with an electric or air powered buffer.
The process of actually polishing and make your intake manifold look extra nice is the easiest part, as the dirty part is over!
Are there alternatives to sanding and polishing an intake manifold?
There definitely are. For people who don't want to spend all the time and effort necessary to clean the exterior, it is possible to paint or powder coat a manifold. These processes make dust and dirt much easier to just wipe off when necessary. Many people who are thinking about polishing their manifold like the original look – and painting or powdercoating doesn't quite achieve this.
Another way: Vibration
There is a less dirty and dusty way to clean your intake manifold, though it doesn't actually “polish” it. Some shops have tubs that provide vibration that can be more effective on delicate parts for your engine, especially if you feel like you don't have a steady hand or the machinery for polishing in your garage.
These tubs vibrate the intake manifold at high speed, and have the goal of knocking the dirt, grime, and carbon out into a waste area that thankfully, you probably don't have to deal with personally. These machines are expensive and often specialized, so unless you are a very serious auto worker, you probably won't have or need one in your garage.
Want to know more? Consider calling or contact your local auto performance shop to see if they have one.
More simple ways to polish your intake manifold
If your intake manifold isn't all that dirty, a simple buffing with a buffing pad an help retain shine. This is moreso if you have recently added a new manifold or otherwise have cleaned it recently – and especially if you don't drive the vehicle that much. These are the kinds of finishing touches mostly left for people who attend auto shows and leave their hoods open to show off the engine.
How long will sanding and polishing in my garage take?
Probably at least several hours. The process of slow because you'll want to start with the lightest grit possible first, and because the intake is probably quite dirty. You'll also be cleaning up in the process. Several people we've read about took an hour or two every night for a whole week to complete the entire process, though that does involve letting it dry and making it look nice and shiny first.
Expect to spend a whole day on it if you have the time and no delays. It is worth saying that many car owners do this just once during the lifetime of their vehicle (unless it is a show car) because the process is lengthy, gross and doesn't add much if anything to the performance of the vehicle.
Polishing the interior of the manifold is much faster because there is only so much you can do, and because you can't readily sand the interior without considerably more work.
How do I keep clean while sanding and polishing?
Our suggestion here is to take frequent breaks and wash down the exterior of the intake manifold as you go. This is to keep from re-sanding and polishing the same areas.
To keep the junk from your intake manifold from getting all over, we suggest just placing plastic sheets on anything you don't want covered in dust and dirt.
Just know that part of the goal is to get what might by years, if not decades, of road junk off of metal, so expect lots of stuff to fly off. This is why we highly recommend eye protection and ear protection. You could also consider wearing clothes you don't care about.
Are there any types of intake manifold I shouldn't grind?
Be careful if any part of your intake manifold is plastic. In the case of plastic, which is unlikely, you'll want to basically wash it off as any grinding will beat it up well.
How often should I polish the intake manifold?
If you are driving around a true “show car” you might end up with polishing your intake manifold more often, but with far less mess. Most people who report a long, dirty process also don't clean their intake manifold but once.
An average driver who notices performance issues with their vehicle and identifies the intake manifold as a problem might need to polish once or twice in the lifetime of the vehicle.
We can't blame people for wanting to polish the exterior though. A thoroughly polished intake manifold does look very nice and original – and a sign that the owner (or someone) is very dedicated to keeping the vehicle looking nice and running right!
Cleaners to use when polishing an intake manifold
For the interior, do a little research. We suggested Purple Power, but there are other products out there. We've learned that Purple Power isn't great for the environment, and unfortunately, if you spill it, the color is all too attractive to kids and dogs who could have some harm if they were to drink it by accident. Do some research and find what fits your needs and surroundings the best.
Why would I need a ventilator to polish my intake manifold?
You don't want carbonization or whatever is leftover in your intake manifold in your mouth and lungs. It's not the worst for you, but the presence of dust and dirt flying around is certain to make you uncomfortable and potentially slow you down.
About The Author
I've spent many years selling cars, working with auto detailers, mechanics, dealership service teams, quoting and researching car insurance, modding my own cars, and much more.Read More About Charles Redding