Head work

From GM Wiki

Contents 1 Introduction 1.1 What is a port and polish job? 2 Past the basics 2.1 Extrude Hone 2.2 Misconception of polishing 2.3 Areas to touch and not to 2.4 Final Notes on Porting 2.5 Valve Job 2.6 Important Information 3 Tools 3.1 Electric Die Grinder 3.2 Rotozip 3.3 1/4" Air Die Grinder 3.4 Dremel 4 Bits 4.1 Carbide Burrs 4.2 Cartridge Rolls 4.3 Mounted Stones 4.4 Flap Wheels 4.5 What I use 5 Walkthrough 5.1 Intake Side 5.2 Exhaust Side

Introduction

This guide was restored with saved copies from 60degreev6.com. It has been completely reformatted to fit the wiki, and many errors (spelling, grammar, etc.) have been corrected.

There is a lot of information on the internet on this subject, so we will give the information as simply as possible. There will be links to more detailed info for those that want to know.

What is a port and polish job?

Porting is the process of removing material. Generally, this is a port match, or gasket match. Port matching and gasket matching are just like they sound, you are opening up the ports to match each other between parts. With a gasket match, you use the gasket as a template to cut away the port. You can see the stock lower 3.1 manifold port vs the gasket here.

The same is done for the head, and that would be a gasket matched lower intake to head. This is really just the start though. Making the ports larger to match helps reduce turbulence, but it is just the beginning.

Polishing is possibly the most misunderstood part of a port and polish. There are some parts you want to polish, but there are others that you want to keep a rough surface on. We will get into that a bit later. Polishing has its place, and all you need to know is that its smoothing the metal, not really removing the metal.

Past the basics

Instead of rewriting whats already out there, we will simply link you to some VERY good information.

Essential basics: Standard Abrasives DIY head port page.

Theory that should get you thinking: Endyn page for a honda motor, but the concepts are what you want

Extrude Hone

The idea behind extrude hone, is that you can port match all day long, but if the runners themselves aren't any larger than stock, you aren't going to flow a lot more over stock. The process isn't cheap, and may not be worth the gains you would expect for the money. There are not first hand accounts of this work being done to relate, so you are really on your own for guessing what the gains may be.

You can do a decent job on your own with some intake manifolds, with a long extension for your die grinder or dremel tool. A sand blaster is what I personally used to smooth up the runners a bit from the casting finish.

Misconception of polishing

Just in case it wasn't brought up in the links from the first page, or you didn't read them, there is a negative side to polishing everything you see. If fuel goes past it, you don't want it polished. When fuel hits a smooth surface, it can come out of suspension (atomization) and drip along the wall. This isn't good for fuel delivery, as it will not burn as efficiently or at all. It is best to not polish the intake ports on the heads, or the lower intake manifold after the fuel injector. You can port them out, but make sure to go over the area with 80-120 grit grinding stones (or flaps for alum heads).

The rest of the manifold should be fine to polish, as well as the exhaust port. The exhaust ports however, don't gain too much from polishing them, as the port design matters more after the exhaust builds up a layer on the walls anyway.

Areas to touch and not to

I think it is important to know that you can hurt flow, in numbers and quality, from porting the wrong parts. Using the 3.1 heads as a guideline (because the ports are larger than the DOHC for visuals), I will point out some important areas.

With that picture open, you will see 3 areas labeled.

1. The top of the port. This is a high flow area and should have more attention paid to it than the floor, which is something you want to leave alone (almost completely). The sides of the port are a safe bet to do some clean up work as well.

2. Leave this part alone as much as possible. This is called the short side radius, and the airflow over this section is much lower than anywhere else. If you cut down the floor of the port you will hurt air flow! The air wont be able to make a sharp turn on this short side radius, and will cause some pretty bad turbulence right above the valve seat. No thanks!

3. This is the high flow area of the valve seat. You want this area to have a smooth transition from port to seat to combustion chamber.

Final Notes on Porting

For the exhaust manifolds, if you decide to port match the exhaust to the heads, you will be doing yourself more harm than good. You want to have a difference between the ports so that the exhaust gases don't end up back in your combustion chamber due to the exhaust pulse. The proper way to "port match" would be to have a larger manifold port than the exhaust port on the head.

This same theory applies to the intake as well, thought the effect may not be as severe. It is best to have the port on the head slightly larger than the lower intake manifold, and you want the lower intake manifold port slightly larger than the plenum. It is ok to perfectly port match them, but it is best to err in favor of small to large, not large to small for intake flow.

Valve Job

This isn't something you will most likely be doing yourself. A valve job requires precise angles to be put onto the valve seats with a grinder. The basic valve job is a 3 angle job, with the "race" version being a 5 angle. I will go into this further once I dig up some pictures as well as the exact angles for each type.

Important Information

For an idea of the tools you will need to start this project, please check out the next section: Tools. The section on how to do port work will give you some more valuable information and links. I also want to say that this is by no means the BEST way to port heads. As of this writing, I do not have the flow bench setup so this is more or less a walkthrough for how I have done my heads and this particular set.

Tools

Electric Die Grinder

Got this from harborfreight.com $50, long snout, 1/4" chuck.

Pros

• 1/4" inch chuck
• Comparatively cheap
• Easy to work with, powerful
• Very easy to control with 2 hands

Cons

• Single speed only: 25,000rpm
• Crappy collet system that makes bits wobble (this particular one, professional ones are better but at $200 and up)

You can fix the speed issue by making a $20 speed control. Put a 5 amp ceiling fan rheostat and a single plug outlet in a dual gang box with cover. This works great, but the collet system still sucks. So I returned it.

Rotozip

I bought one of these for Christmas to use as a general purpose tool. Turns out it makes a kick ass head porting tool. If your gonna buy one, I'd suggest the "revolution" which has an electronic 4speed control.. 15k, 20k, 25k and 30krpm. I have the "rebel" 2spd, and it works great.

Pros

• 1/4" chuck
• Powerful
• Variable speed
• Collet system is dead center, no wobbling even at 25krpm
• Can also be used as an angle grinder with the attachment
• The scotch brite pads on this thing cant be beat for removing gasket material
• 1yr warranty and after that its a $36 replacement fee

Cons

• Expensive, but a lot cheaper than a variable speed die grinder
• Needs long bits since its a short snout
• If it breaks within a year get it replaced under warranty! Mine had a few problems and I waited too late.

1/4" Air Die Grinder

This is a great tool to use for head porting, and most shops use air tools for most everything. You will need a compressor to run it, and it must provide plenty of airflow (CFM, not psi) to keep it going since it's almost constantly on. I used a 3hp 8 gallon compressor and it was just enough to work good without running the compressor all the time. (Ben: I use a 5 hp 20 gallon compressor and a mini die grinder from Eastwoodco. The cost was 20 bucks plus the bits. It's easy to vary the speed for the cross buffs and sand paper rolls by turning the air pressure down some. You can also push the lever down less but I wouldn't advise it unless you have used the die grinder for a while.)

Pros

• Cheap initial cost for the tool
• 1/4" chuck
• Does not "grab" work
• Smaller so it's easier to maneuver and see around
• Lightweight

Cons

• Must also own or buy a compressor, but that has its advantages
• Noisy depending on compressor location
• Must oil the tool before use each day

A water separator in the line would help. Water and oil will shoot out the back of the grinder if you don't, and most of the time that means its on your shirt or in your eye.

Dremel

Most everybody has one, and since they already have it figure "Why buy something else when I can port heads with this?". Yes you can use it, but its the wrong tool for the job. I've used this myself for head porting. I'm sure everyone has, but once you step up to a 1/4" grinder you then realize why the Dremel was not meant for head porting. (Ben: I killed a set of heads with a dremel tool. I butchered an intake manifold or 2 as well.)

Pros

• Small
• Lightweight
• You probably already have one
• Durable (Ben: Durable....not for me they aren't!)

Cons

• 1/8" chuck system
• Underpowered for this kind of job, will take forever
• Limited bits available and they are way too short
• Quality of work is equal to a butter knife on an ice sculpture

Bits

Carbide Burrs

Best for quick material removal, depending on cut type (single cut or dual cut). Available in many shapes and sizes (flame, round, tree, tapered, straight) so you can do any type of porting with these. They do cost a bit, but they pretty much last forever and don't need sharpening. You will need some type of lubricant while porting, such as Grinders Grease Eastwood or WD-40. Dual cut is best for iron heads, and aluminum heads can take dual or single cut. They do leave a semi-rough finish, so go back over with a flap wheel or cartridge roll. Since these bits remove material quickly, stop often to check your work. You can easily create pits if the tool stays in one place for too long, and you can't add material back. Make sure you have a good hold on the tool, some of these bits used in an electric grinder can grab the work and easily ruin a valve seat if your not careful.

Cartridge Rolls

Best for moderate material removal and finish work. Available in many shapes (straight, tapered), sizes (3/8" - 1" thick, 3/4" to 2" long), and grits (40, 80, 120). Must be used with an appropriate mandrel. Small cost involved depending on shape/size but have a short lifespan. You can port heads entirely with these if your just doing touch-up work on a stock head, but major porting should be left to carbide burrs or stones.

Mounted Stones

Use only on Iron heads, aluminum clogs stones and renders them useless. Moderate material removal, but also less chance to make mistakes. Many shapes/sizes available and can be dressed or reshaped to best suit the application. Low cost, and moderate lifespan. Be sure to check manufacturers suggested speeds, some low quality stones can fly off the mandrel if used at too high a speed.

Flap Wheels

Also 3M Stars: These are mainly used for finish work on ports after your done porting. They also come in different sizes and grits, and must be used with appropriate mandrel. They last quite a while. Some must be used with a lubricant and low speeds for best lifespan and finish.

You can buy these tools most anywhere, but the bits and things are harder to come by. I buy my stuff from [1] Goto the site and have them send you a catalog, you'll love it. You can also get stuff from [2] and [3]

Generally J&L has the best prices, especially if you buy in bulk, but you almost certainly need the catalog since there are so many items it renders the online catalog useless.

What I use

Rotozip:

Cartridge rolls

• 1/2" x 1" x 1/8"(center hole for mandrel) 120grit straight
• 3/8" x 1" x 1/8" 120grit tapered
• 1/4" x 1 1/2" x 1/8" 120grit straight
• 4" / 6" / 8" x 1/4"shaft 1/8"x1" roll mandrel

Burrs

• 1/2" x 1" tree single cut x 6" long 1/4"shank
• 1/4" x 1/4" ball singe cut x 3" long 1/4" shank

3M star

• 1 1/2" stars on 8" mandrel. I haven't used them yet, but I have them for when I need them.

Walkthrough

Intake Side

This is the head, already decked and cleaned and checked for cracks. This is very important, because there is no point in porting a set of heads only to find out there is a crack in it and you can't use it. Decking the head is a good idea because of the combustion chamber work being done later.

Here is the intake port side of the head matched up with the gasket. 2 of the ports are pretty close, but that third port has some real issues. The part you can�t see is that the gasket is smaller on one side as well so not only will some head side removal be required, but the gasket needs some modifying as well.

This is the bit I use with the air die grinder. It�s just a tree shaped sand paper roll. You can use a straight one that is worn down and rounded as well, which is what I did this time to conserve the tree shaped bit.

After some smoothing it�s obvious that the casting flaw on this port is pretty deep. Since I am not to the point of enlarging the port itself, I have left a small amount of it here. There is no need to do every step all out at once, which I learned the hard way. For NA heads, you really do NOT want to hog these out. If you are going for all out top end power though, you can go a bit further than I will be demonstrating at this time.

(Full-size image missing) Here is another angle of the same port, looking through the intake valve bowl. It shows the pain in the ass part of the port as well, which you will have to deal with later.

(Full-size image missing) After cleaning up the intake manifold side a bit, I start on the bowl side. If you look carefully, the bright ring just inside the intake seat is the lip you want to eliminate. Although it�s not as bad for a lip on the intake side as it is for the exhaust side, the turbulence created from flowing over it makes it worth smoothing out.

I use a straight sand paper roll for this. It is important that you keep the roll moving at all times in an even and circular fashion around the throat area. Check often so you know when there is no more lip. It is EXTREMELY important that you don�t cause a lip in the opposite direction, as that will create more of a problem than you are eliminating. It�s possible to take away metal on the steel valve seats but it�s much easier to work with aluminum.

This is the bowl area after matching the seat with the throat. Picture doesn�t show this too well but the untouched area between the throat blend and the initial port work has a significant drop off. The area just inside the throat is larger than the throat area itself, which means some blending is in order to at least remove the sharp transition.

I use a smaller rough sand paper roll for the initial blending. After I have got it to a nice bell mouthed transition, a well used large sand paper roll works to finish it up before the final steps which have a ways to go.

This is what it looks like blended for the most part. I have already gone over it some with a large rough cross buff. It�s important to use your finger to feel the work you do. You can feel the smallest bump and indentation and any other flaws.

This is the cross buff that I use to finish blending. Although I am not done with the blending, it makes any irregularities in the port easier to feel with my finger.

After get the port fairly cleaned up, its time to sand blast (if you don�t have a sandblaster, don�t worry, it serves no real important purpose on heads). I use it to remove all the carbon traces which can deceive the eyes a bit. Before sandblasting it is important to mask off the valve seats and prevent sand from wearing the inside of the valve guides.

Back to my favorite part of the intake bowl...not really. I used a tapered sand paper roll (the tree shaped one) to get to as much of the rough bumpy area as possible. It�s nearly impossible to get everything, even with the narrow rolls I have, and the cross buffs. Don't worry too much about touching every area, just focus on what you can get and don�t take away to much material here.

This is how much I did to the hard side of the bowl. It's just enough to remove the bumps .

(Full-size image missing)After getting the bowl area 99% done, I was ready to finish up the port side of things. Before I had left it with a slight amount of casting flaw, which as you can see is now gone. The final port will be done with the gasket matching, which I save for last. The reason I didn�t remove the entire casting flaw the first time was to make sure I could make a smooth transition from port to bowl to valve seat. Doing any part to much will mean I may find myself going back and forth trying to even things out. It�s easier to do this on a much smaller scale (though you can get lucky, but why take a chance?).

You will be happy to know the exhaust side of the head isn't as complex, unless you want to make it that way.

Exhaust Side

The exhaust side of the heads presents a different objective from the intake side. The flow will be coming from the combustion chamber and exiting the port face. You do NOT want to gasket match the exhaust side, because the exhaust pulses will have a tendency to reflect back towards the exhaust valve at certain RPMs (stock manifolds are much worse for this than a good set of equal length headers too). This is called recursion, and the best way to prevent it is to have a smaller exhaust port than the manifold/header.

So let's get on with the walkthrough.

This is the exhaust bowl area stock. You will probably find that some ports are much better matched to the valve seat than others. This particular bowl isn't too bad other than the obvious casting mark.

To get things started, I use a straight sand paper roll. This will show you where the areas aren't flush, and whether it�s a raise or a dip from the seat to the bowl area. Dip is better than a raise, so for the cases of a recessed area I would just touch it up to smooth the area. You do not want to make the recessed area any deeper than you have to. For the raised areas, you want to make it even with the valve seat. Don�t venture too far into the bowl just yet though.

You can see where the sane paper roll isn�t touching the metal right behind the valve seat. It�s hard to tell but this case the bowl area needs to be sanded down to be flush. This picture was taken after 5 revolutions around the seat/bowl.

Same bowl, only completely flush. Doesn�t that look MUCH nicer? It�s important to make it uniform and fluid around the entire valve seat. Focus more alone the backside since this is where most of the exhaust gases will be flowing.

With the bowl area started nicely, it is now time to begin with the port. Again, no port matching so the goal is to clean up the casting flaws and smooth the port floor without removing more metal than needed. Here is a stock picture.

This is a small amount ground away so you can see the casting flaw I am about to remove. I have included both sides so you can see before and after. (Pictures of opposite side are missing)

After hitting the bowl area and the port area, you will be left with the area around the valve guide and the corner/elbow transition from the bowl to port. I use a small sand paper roll to get into the tighter areas.

You want to try and blend the corner area for a smooth transition without taking away too much metal. This is also the short side radius and follows the same principles as the intake side porting did (it�s not visible in this picture however). What this picture does show is the area around the valve guide that needs to be smoothed out, and the casting line in the bowl area that will need to be cleaned up.

This is how the port will look after the sand paper roll has cleaned up some of the corner.

After I have got most of the exhaust bowl and port cleaned up, I like to sandblast so that I can see where any bumps or casting lines may be hiding under the grit and remaining carbon. It�s not necessary but I have the ability and it is nice to have a uniform wall to see and feel before moving on. To be safe, I mask off the valve seat and put paper towel into the valve guide to protect it.

This is where you need to make a decision. For a boosted application, I would wipe out the protruding valve guide. Even some NA applications could find this useful but its untested and a bit on the extreme side. You can also grind down the aluminum around the guide some for more flow, or round it off and polish it up. I will be grinding it down some and rounding off what is left for these heads.

You really need to attack it from both the port side and the bowl side. I like to use a well worn down straight sand paper roll so that it has a rounded edge. You can use an aluminum cutting carbide from the bowl side but you better be damn careful and know what you are doing. If you are removing the guide from the port, you will have to do this for the sake of time.

If you decide to take it out, this is what it will/should look like. These photos are NOT of the head I am working on.

(Full-size image is missing)I decided to use the carbide cutting bit to make this job a lot easier. The key to using it is to GO SLOW! I make several passes to remove a small amount of metal. The nice thing with the air die grinder is that it stalls when you snag something. Electric would start bouncing all over the place.

This is what it looks like after using the carbide cutter. I kept the same angle as the port flows, which means 2 of them face the same way and the 3rd bowl has it facing the opposite. Next I will be using the sand paper rolls to blend it all together.

The sand paper takes a little while to effectively blend everything together once again. It�s important that all the sharp edges are gone and smoothed out.

After using the sand paper rolls and the cross buffs, this is how the guide looks. This is the best picture I can take for some reason.

I will have to try a better picture later of the finished port. I don't want to clean it up and have to do it again later after I do the combustion chambers. I will say that I used the cross buffs to give the wall a nice mirror finish.