Let’s talk heads for a few minutes. For a primer on head flow theory, check out Vizard’s article that I have added to the end of this post. It is about as complete as any I have found and includes much of the information that I have gleaned from HVH.

There are any number of heads you can choose for your project. Factory iron heads are the cheapest and most common, but they vary considerably in flow. Joe recommended that I stick with the later Vortec style heads as they have several engineering features that make them flow much better than their predecessors. If you are interested in using stock iron heads (either OE SBC or Vortec), check out the article “Guide to Vortec vs OE SBC Heads” also at the end of this post.

There are also many aftermarket heads available, both cast iron and aluminum. Iron is cheaper but heavier and more difficult to port. Aluminum has the advantage of light weight and being easier to work, but the softer material will also make it easier to make a mistake. Both versions (iron or aluminum) come as-cast or CNC’d.

As-cast heads have minimal cleanup done to them and vary according to the quality of the casting. More expensive heads generally have better casting tolerances but not always. Before choosing a set of heads see if you can find someone who actually has a set.

CNC’d heads have been cleaned up using an automated program on a CNC machine. If you are leery about doing your own porting work you probably want to buy CNC’d heads. Hand work can improve a CNC’d head but not nearly as much as an as-cast version. My HVH heads came as-cast, I have included a picture of the intake port of a nice quality cast head and of a CNC’d version of AFR’s 235 heads so you can see the difference.


Nice cast port on the left - CNC AFR 235 on the right

And here is a picture of the inside of a cast intake port at the valve. You can see at the bottom that someone has done some hand work, but the port can still benefit from further work in the areas marked with the yellow arrows. Note particularly the cast valve guide boss which pretty much always needs some work.


Areas for work in a cast port

The ultimate is having a custom shop hand port your heads for you. A good shop can work miracles over what most people can do in their garage, that is why racers pay the bucks to have them do their head work. (Bill at B&R has a set of HVH heads that were hand ported by a local professional who did contract work for HVH, Joe described them as “a work of art.”) Be careful to check out the reputation of a shop before you lay down big money to have heads ported.

And don’t be swayed by a nice polished port. Vizard’s article discusses why. Joe used to say that polish was only a sales feature, for most racing applications HVH actually sandblasted the intake port to rough up the finish. You can polish the chamber and exhaust as that helps keep to keep down carbon buildup. Joe recommended no more than 400 grit for that.

If you have been following this post for a while, you know that I traded work for a set of HVH Double Hump Heads. I found the figures I posted earlier for the HVH heads were slightly off (too low). Here is the actual tag from the box. Since these were as-cast heads there was room for improvement.


HVH Double Hump box label

The HVH heads are not my first plunge into the world of head porting. Joey Martin worked with me on an experiment with Rover heads for my Spitfire project. Joey was the CNC guy at HVH before he moved away. Joey was the one who digitized head designs for CNC porting at HVH and was a pretty decent head porter in his own right. On my Rover heads we started with 145 cfm max flow on the intakes and when Joey was done he had gotten 208. While we did use larger valves most of the increase was in the port shaping (the Rover had tiny ports). So I had confidence in Joey’s ability.

Joey owned me a favor and agreed to clean up and gasket match the intake ports on the HVH heads for me. I would do the exhausts, the combustion chambers and the bowl cleanup with his input and supervision. As I mentioned, this was not my first time porting heads so I was not a neophyte. If this is your first try you probably want to pick up a head from your local u-pull and test on that.

A word about gasket matching. One of the importance considerations when assembling the top end of an engine is making sure that the intake and exhaust ports line up when you assemble the engine. The biggest mistake most people make in the top in in buying and bolting on components WITHOUT CHECKING to see how well the components match. Manufacturing and casting tolerances vary widely so it is pretty common to find a mismatch in even reputable components. You ALWAYS have to check, don’t assume anything.

Gasket matching is the process of using the intake or exhaust gasket as a template for making sure the ports match. It is not a foolproof method, but it is a good place to start (I will go into more detail about matching ports later). I have heard that comment that gasket matching “does not add any horsepower” which is true as far as it goes. The problem is if you don’t match your ports you can wind up LOOSING considerable horsepower if the ports are mismatched. Just think about the effect of a sharp edge sticking out into the air flow ….

Keep in mind that if you are using one of the newer intakes based on fluid dynamics, they may have shaped ports for specific flow characteristics. In that case you might want to avoid changing the shape of the ports. But Joey assured me that on the HVH heads I was using a gasket match would be the best place to start.

First we sent the heads over to HVH to have them “bowl hogged.” This is essentially the process of boring out the throat diameter to the maximum for the valve size and requires special equipment. In general, street heads are bored 0.85 valve diameter and racing heads 0.9. After this the heads went to B&B for a three angle valve job (competition is five which was deemed not necessary for my application). Next the heads came back to me to work on the combustion chambers. I will discuss that in the next post.


Cast chamber after bowl hogging and 3 angle valve job

 

good info! thanks

 

If you want to do your own head porting you are going to have to invest in some tools. It is going to cost you about $250 if you don’t have some of the things you need around the shop already.

First, you will need either an air or electric die grinder. Air die grinders use HUGE amounts of air so if you choose to go that direction be sure you have a compressor large enough to keep up. I have a 5hp 60 gallon compressor which seems to do nicely. Joe swears by an electric grinder. I like the air models for better speed control. You will probably want a regulator if you compressor does not have one.


Electric die grinder

I started by using a standard length Cobalt air grinder but found when I got to the port work that the nose was not long enough to get deep into the ports. I got a model with an extended nose from Harbor Freight for less than $20 on sale and it has become my grinder of choice. So far it has performed flawlessly and gives you a much better grip. The Cobalt came with an adapter for 1/8” shafts (most common is ¼”), so I leave it set up for smaller work like the flap wheel.


Cobalt short air grinder and flap wheel


Long nose air grinder

I also made a wooden stand to hold the heads like the ones they use at HVH. With a wood stand you have less chance of dinging an important head surface. Mine works great and you can clamp it down to the workbench to hold it steady.


Home made work stand

Here is the way the HVH guys held their grinders which is not what I would have done. With the grinder pointed down grab the body with your dominate hand, then grab the extension with your other hand. Reverse your hands if that feels more natural to you. The position seems strange at first but once you get used to it you will find that you have much better control of the tool. You can also lean the top of the tool against your chest to provide even more security.


Tool grip

You are going to need an assortment of bits and sanding rolls. I opted for the Standard Abrasives sanding roll kit (about $65) that contains different grades of sanding rolls and two 3” mandrels. If you are ordering you probably should order a 6” mandrel as well as you are going to need it when you start working on the ports.


Standard Abrasives sanding roll kit

Standard Abrasives has a head porting guide which has some useful information. I have included it in the pdf files at that bottom of the page. The one thing I would suggest different from their recommendations is using carbide bits rather than stones. I have not found stones to last very long and if you are working with aluminum they clog up pretty quickly. They work better on steel.

Next you want a decent set of carbide bits. I opted for an assortment from Neiko and they have worked well for aluminum (About $70 - one is out of the case). I have done some minor work with them on steel with good results. If you spray them with WD40 periodically it extends the life and keeps the aluminum chips from building up.


Neiko bit set

Might as well order a six inch bit as well as you are going to need it for port work. My favorite is SGS Tool’s 16353 which is pricy at $25 but great for getting down inside ports


SGS 16353 6" bit

You will need some sandpaper of various grades for hand work. I also used a flap wheel for my chamber work. It is the small tool in the picture with the Cobalt die grinder above. And a set of old valves slightly smaller than you plan to protect the valve job. All it takes is a nick to cause a problem. I think I used a 1.94 and 1.5 for the 2.02 and 1.6 valves I was planning to use. Bill at B&R had plenty of used ones laying around.

And at some point you will want a carbide stylus for marking shapes. You can use dye for this purpose but I found that a Sharpie works about as well. For some processes you can use blue masking tape which was easier for me to see. Just make sure you score as lightly as possible to avoid causing a sealing problem.


Carbide scribe

So now you are ready to start porting. I elected to start on the chambers while I waited on Joey to have time for the heads. Here is the process with pictures. My primary aim was to smooth the airflow and remove any sharp ridges without changing the shape of the combustion chamber. The first picture is of the as cast chamber. (Note: all the pictures are not of the same chamber, just the best ones I had of each step of the process)


As cast chamber after bowl hogging

I started with a sanding roll to take down the roughest sections. Note: It helps to have an old head gasket to check the proximity of your chamber to the bore. You can also mark the bore if you are concerned about clearance. Mine cleared with no problems.


Sanding roll work

Next the flap wheel was used to smooth out the casting surface.


Flap wheel work

Now on to hand sanding. First the 150 grit.


Hand sanding 150 grit

Then the finish work with 400.


Hand sanding 400 grit

I found that it took between 2 and 3 hours per head to take the chambers from start to finish. I took my time and took frequent breaks to avoid making mistakes. I was pleased with the final result and Joey thought they looked excellent when I sent the heads to him for the next step, gasket matching the intake ports.

 

Joey of HVH owed me a favor so he offered to take the heads after I had completed the bowl polishing and do the gasket match on the intake ports. With his hectic schedule it took him a couple of weeks to get to them. Here are some pictures of the heads as I got them back from Joey.


Joey's intake port work


Intake port gasket match

The intake ports look real nice. Joey admits that he went a little wild on the port size but a little wild does not both me. He also got the intake bowls cleaned up and they look very smooth.


Intake bowl blending

Here is what the worst intake and exhaust bowl looked like after the bowl hogging and before blending. The red arrows are places that need to be blended. You can compare this picture with the previous one to see what Joey did. The yellow areas indicate the short turn radius. In most head castings there is a ridge left here by the casting process. If you have a ridge problem here you can very easily feel it with your finger.


Bowl areas needing work

You want to be very careful with the short turn and not take too much off, just smooth it down. While some argue that manufacturers leave a lip here for flow purposes Joey said he had never seen a head that did not improve flow from smoothing the ridge in the short turn.

Joey had cleaned up the intake bowls so I set to work on the exhausts. Here is a typical picture of what a cast exhaust boss looks like. As I mentioned, the HVH head castings are pretty good as they come from the factory.


As cast valve guide boss

The black tape surrounding the valve seat is Gorilla Tape. I know, it looks funky but I didn’t want to nick a valve seat and the Gorilla Tape really works. I have also used it to mask off areas when I am bead blasting, works well for that too! Here is the exhaust boss after using the carbide cutter.


Carbide cutter work

And here it is after doing the rough sanding (using a sanding roll). I did do a finish sanding with a finer grit but didn’t think to take a picture


Rough sanding roll work

 

Good info -- added to my Amazon wish list!

 

If you have any trouble removing the mastic residue WD-40 does the job well (Gorilla Tape is seriously sticky). Another one of those things every shop should have. I love it when something designed for one purpose works well for a completely different situation.

 

WD-40 is good for that, but I've found 3M Adhesive Cleaner works far better, and as a bonus does not leave a residue. It's safe on most cured finishes as well. I get it at my local auto body supply house.

 

Having the intake side of the heads finished, I turned to the intake manifold. The first thing is to check the alignment of the manifold ports to the ports on the head. For this you will need to mock the heads up on the block (preferably the one you are using) with a set of used (compressed) head gaskets of the proper thickness, and a set of gaskets for the intake.

If you are using a single plane manifold, it is often possible to look down the ports through the intake manifold once everything is mocked up and with a small mirror and goose neck flashlight actually see where the ports are mismatched. The more radical the intake the easier this is. But if you are using a dual plane manifold this is not going to work. So you have to go through the tedious process of marking all the ports on the edge of the head and manifold and then compare your markings (keeping the marks out of the sealing area). Here is a summary of that process.

To mark the ports in the head, use a straight edge and mark the horizontal height of the ports on the end of the head.


Port height marked

Do the same with the intake manifold. Then with a square mark the vertical locations of the ports in the head and intake.


Use a square to locate match marks


Make vertical marks you can see with the manifold assembled.

Next mount the heads on the engine with your used head gaskets (U-pull gives them away for free here). Then bolt the intake to the heads using the proper gasket and snug them down. Now, compare your sets of marks and see how much your ports are off.

Uh oh! Serious problem. There was a significant mismatch vertically and horizontally of the ports in the head and on the intake. I went through the process of checking the dimensions of the ports with my micrometer and came up with the following sketch.


Height mismatch sketch

I emailed Joey in a panic with a picture of the sketch. His response was “I have seen way worse, that can fixed.” OK, blood pressure starts to come down.

I talked to Joe later who reminded me that this kind of problem is why shops like HVH are in business. Guys who simply buy parts and bolt them on never check things like this and then when their engine runs like crap they come in to see what is wrong. Most people, however, never know that they are losing serious power because the new parts result in an improvement that “feels” significant over what they had. Be wary when someone says their engine “feels” like it has great power. Unless you have a dyno sheet you really don’t know what you have.

The solution to the height issue was to match the ports in the intake to the head and then adjust the port height in the intake manifold. There was enough metal in the intake manifold that this was not a problem.

But there was also a significant mismatch in the vertical sides of the ports. One divider between the ports was offset so much I could not compensate by adjusting the port, there would have been nothing left. This problem required a little more radical solution. After a lot of head scratching and figuring, I determined that the problem was that the mounting holes in the intake manifold were off by about 1/8”.

I happened to have a friend (Eddie Rickenbacker said, “I would rather have a million friends than a million dollars”) who had a machine shop. He volunteered to put the intake on his mill and lengthen the holes by 1/8” so I could shift the alignment. (Note: if you shift the manifold too much you start to run into clearance problems with other things, best get another manifold in that case, but it may have the same problem!)


Slotted mounting holes to align the ports

That did the trick. Now I was able to get everything to line up horizontally and vertically. I laid out everything with tape and went to work. This took a fair bit of effort as the metal shaving indicate.


Intake manifold port work

I added a match marks to the head and manifold edge to indicate the proper alignment with the new slotted holes when they are finally assembled (sorry, forgot to take a picture) and I was back in business.

The next task was to add the plenum divider in the manifold. Joe had an HVH Street Sweeper on hand and we matched the upper edge to that and then shaped the opening according to HVH’s tests.


Plenum window matched to HVH Street Sweeper

Boy I’m sure glad that is done. I hope we don’t run into any more problems. Little did I know …. More next post.

 

For anyone else trying to accomplish this task I can give you a fairly easy and much more accurate method that works identically with an open plenum OR a side-by-side manifold where you cannot actually "see" the port alignment. There is really no need to look inside at all.

Below in red is a copy of a previous post I made explaining this method, we do it this way on almost every hi-perf build.

Thanks, Gary in N.Y.

P.S. This procedure is 100% accurate, no better way to accomplish the goal.

(Quote) The ONLY effective way to a true 'Port-Match".

1-Have heads pre-mounted on block to be used, with both head gaskets in place.

2-Use 2 pieces of masking tape or 2 spots of silicone and position intake gaskets in place.

3-At this point make sure the intake gaskets (marked R/L) fit the head ports the way you want them.

4-Lay the intake in place with 4 corner bolts, at this time you'll know if bolt location is OK.

5-Snug the bolts down, and using a 1/8" drill, drill 4 holes (1 at each corner) through the intake making sure where you drill you will hit the gasket (don't drill where there is no gasket below).

6-Let the drill tip go right through the gasket and stop on the head. Remove the intake and lay the gaskets on the respective sides as templates, (we use 1/8" "cleco" buttons to mount the gaskets back on the intake sides) and you can use (2) 1/8" drill bits for alignment. With the gaskets mounted on the intake, simply scribe out the ports on the intake and "grind away". By using this method we can literally leave a perfect "overhang" (reversion-wall) on the intake runner of .020"/.030" or we can make it "straight-wall" deal, no "overhang"!!

In simpler terms, the head port is slightly larger than the intake port. It's your choice to line up the port perfectly or leave the "overhang".
The entire procedure takes about 20/30 minutes to achieve and guarantees a "perfect" fit on the final ***'y. This procedure can be done on assembled long blocks that have been running and getting an intake change. We run the intake port "inside" the head port for anti-reversion only on street engines and not on the “track only" units due to the higher VE of race prepared engines.

Thanks, Gary in N.Y.

P.S. There is no other accurate way (that I'm aware of after 38+ years of engine building) to get "perfect" port alignment, period! (End quote)