Originally Posted by BurlyHatch

I'm brand-new to this forum (used to be on JDMcivic.com) but hopefully I can become a consistent contributor. I'm bored tonight, so I figured I write up a little basic head porting article. Power is in the heads, and if you're on a budget you can free up as much as 20 hp just from porting and polishing. Obviously there are more "sophisticated" ways of doing this....but double digit horsepower for the cost of common shop tools? It sounds good to me. And also it doesn't take a brain scientist to port heads. The #1 most important thing is attention to detail. Oh yea, and a little bit of time on your hands...so here we go, I'm not garunteeing (sp?) perfection! hehe
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One of the most important rules of high performance building is to remember that the horsepower is in the heads. The total investment in the cylinder heads of a high performance engine can represent a significant portion of the entire engine budget, and in the search for horsepower, you can't go wrong ordering a set of heads from one of the cylinder head gurus. But what if your budget is not within the "guru" price range? Noticeable gains can still be made by the do-it-yourselfer through careful portwork and attention to detail. Follow along as I walk you through the basics of head porting.

This is a description of basic porting techniques used to port a stock Honda/Acura casting. These include the B-series, D-series, and H-series, with either stock or aftermarket valves. Heads with larger valves should have much more porting work done in order to flow to their full potential. I am not a professional. The head porter's trade is truly one of a Black Art form. Don't expect your heads to flow as well as a professional's would.

I like to use a rotary file of different shapes (ball, acorn, and tulip shape). For finishing, I use a sanding roll and small flap wheels (80grit). These are all available to fit a Dremel Moto tool, available at any well-equipped hobby or hardware store. To keep things the identical, I like to do one step at a time to all 4 ports before moving on to the next step. This process usually takes approximately 10-20 hrs. to complete.

Valves and Seats
The use of stainless steel valves will always improve flow over standard stock valves, as they have a much tighter radius on the backside, allowing for less obstruction at the opening when the valves are open at low lifts. A good 3-4-5-angle valve job will enhance the flow improvement even more. You can pay a professional to do this work. I have access to some really nice grinding stones at work and have good success grinding the valve angles by hand, with the exception of the sealing 45 degree angle. I leave that one alone.

Port and Chamber Area Around the Seat
The valve seats are steel inserts pressed into the aluminum casting. There is usually a mismatch of metal in the port and in the combustion chamber. Take time to blend the port and chamber until the step (mismatch) is gone, using your finger to feel for imperfections. When working around the valve seat, take extreme care not to accidentally nick the 45 degree angle in the set, or you will be taking the head to the machine shop for dressing the seat. If the heads are used, the do the port work first.

Combustion Chambers
Too much deck height is a bad thing, resulting in loss of turbulence at TDC when the mixture is ignited and reduce combustion efficiency. Deep combustion chambers are another problem, as they tend to shroud the valves giving very little room for flow around the valve into the chamber. I like to lay back both the plug side and non-plug side of the chamber by widening the angles. I also unshroud the valves by opening the sides of the chamber up to the cylinder bore diameter. I then blend all this together, smoothing all imperfections and casting marks. This means that the chamber is opened up all the way around, making for a much clearer entry for gasses into the cylinder (and exit for the exhaust). I then flycut the heads to get the desired chamber CC's (with .050" - .070" deck height). I then use a flapwheel to remove the sharp edge all the way around. Take care not to round the sides where the cylinder will seal against the head. It is a good idea to scribe a line around the head where the cyl will meet the head, and to drop some junk valves into the heads to protect the valve seats while working in the chambers.

The goal is to provide the best port-match for the specific valve. "Hogging it out" is not the goal. The stock size port does not need to be enlarged very much to get good results, and too big of a port will cause a loss of port velocity and create unwanted turbulence. The goal is to reduce the restriction of the port.

Set the head in front of you with the intake flange facing you (right side up). The ports are round, and we are going to make them oval in the direction of the sparkplug holes, similar to a "V" shape. If you have a intake gasket or pattern to borrow, now is the time to draw/scribe it out onto the intake flange. Hold the grinder perpendicular to the flange and open up the ports to the new port shape. Don't worry about blending into the port yet. Take your time and make all the port openings look the same.

Set the acorn file out as far as you can in the grinder to give maximum reach into the port. On most heads the port has a casting part line right above the intake guide boss. This part line makes for a major corner right above the guide boss blocking any flow trying to go over top of the guide. You will want to blend this corner away by plunging the grinder down through the port going over top of the guide boss. Once through, work from the chamber side of the port to blend the contour. There is a fair amount of metal to remove here so take your time and study the port closely. The goal is to make the port above the guide look like it does below the guide, in effect straightening the port. This will open up a new flow path for intake charge. I also like to thin the intake guide boss, as it does very little anyway. Shape the metal into a nice teardrop shape around the guide, working from both ends of the port.

Once the major porting has been performed, blend the whole port together, removing all the bumps and corners, radiusing the port into the new openings. Use your finger to feel for irregularities. The contour should be one nice smooth blend all the way to the valve seat. Work slowly!

Exhaust Ports
I pretty much go by the book here. Without removing too much guide boss material, I like to contour the boss much in the same way that we did the intake bosses. Because the boss takes up so much of the port in that area, it helps flow to widen (or squeeze) the port around the boss. Working from the seat side of the port, start widening the port on either side of the boss just below the seat. You can blend these wide pockets into the port from the exit flange side. There is a sharp edge on most heads on the inside radius of the port, and it is almost impossible to see (you have to use your finger to find it). Tighten-up the inside radius, leading away from the seat, blending this edge away. Do not take too much material away here or there will not be enough left to support the seat properly. Lastly, open up the port at the header flange. Use an appropriate size exhaust gasket for this pattern.

Finishing Up

I like using a flapwheel wherever I can, as they do a great job of smoothing out the bumps and blending everything (and they last a long time). If the flapwheel will not smooth it out, go back to the rotary file. If you have done it right, you will have a professional looking port job. With any luck you will have one that flows almost as good as a professional port job as well.

Match-Porting
To take full benefit of your efforts it is important to match-port the intake manifolds. I use the same pattern gasket and transfer the port shape to the manifold base.


Good luck and remember, this is free personal advice.

Originally Posted by HEAD

I don't know if you grind everyday but you certainly explained it well. I hope you don't mind but I would like to say that I perfer using a cartrige roll over a flapper wheel 60 grit on intake 120 on the exhaust mostly for time concerns it takes way to long to sand a port out with a flapper(my opinion not fact)and to me it's also real hard to get out all the grinding marks using the flapper but I think it also really depends how much patience you have for such a thing. As far as grinding around the seat if you get some junk valves with the same head diameter and take them to a machine shop have them cut the 45 angle till there is no margin and the valve is almost razor sharp it will cover the seat and you can blend the valve job in alot nicer.
As far as sanding the intake side I have never seen more than a couple of cfm from doing it I think it does help using the flap wheel over the short turn because most of the time using a cartrige roll in this area will leave a point at the top of the turn and I would also like to see this done to blend the valve job in, but I have never seen it hurt flow or performance by sanding the port, I would say if you went crazy on polishing and mirror polished it that would hurt atomization causing the fuel to puddle or fall out of suspention . but that's just my opinion.
oh I almost forgot to say for another porting tip would be if you are grinding with an aluminum bit go back over it with a cast iron bit slowly when I say this I mean slow the speed of the grinder down and push a little harder this will make it either A. a smoother finish than the aluminum bit gave(it's actually preety close to polishing it) or..
B. will make it easier for you to polish
Good Luck to those that try!And thanks for the good thread I enjoyed reading it!