MA12 cylinder head porting?

As far as porting the ma12 cylinder head goes has anyone here on MSC done this and have any knowledge to share in the subject?

Especially the intake ports hence they're ovalized 30mm by 34mm(not a confirmed number) I'd figure to ease the breathing by taking them up to the region about 34-38mm. This is a lot of material to remove no doubt and I'm not completely sure of how much one can dig until you breach into the oil/water canals.
Of course, porting the exhaust will come in order as the intake has been machined.

Any help on the subject would be appreciated and hopefully of good use of others.

Kind regards, Aron.
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So I'm back again and since no one replied on my thread I decided that I would give it a go anyway and thought I would share my work if anyone else would be interested in the same modification of their MA12 cylinder head in the purpose of performance enhancement.

This is by far not the utmost serious work on a cylinder head that could be done, take this to account while reading the content below that everything shown below was done while I was in a very tight schedule since I really needed the head on my daily driver and up and running ASAP hence no deeper thought nor calculations and no flow testing has been executed on this head. All the work is done fluently and by "free hand" as I work my way through.

Starting with the exhaust there is some cast bumps an edges that have the potential of easing the escape of exhaust gases.
Especially the second exhaust port(the ovalized one shown in Figure 1) where the EGR port is placed on the manifold we have a cast bump with its sole purpose to create a more turbulent flow(a slower gas flow with more whirly flow lines). As we aim for a improvement of performance and this particular engine is a naturally aspirated one we'd like a fast, steady and as laminar gas escape flow as possible with as little back pressure from the exhaust system as possible.

Figure 1

With that mentioned, we'll grind this cast bump away(the result can be seen in Figure 2).

Figure 2

If we look down the exhaust port from the combustion chamber we'll see a quite nasty edge(shown in Figure 3) that are working against our goal with this work(it's slowing the exhaust gases down).

Figure 3

And thereby we'll remove this as well while creating a smooth pass from the valve seat to the exhaust port orifice shown in Figure 4.


The crosscut area of the exhaust port across the valve steering is reducing and creating a form of a ledge in the port, this reduced crosscut area creates an increase in pressure of the gas and this leads to an increase of back pressure when the exhaust gas is moving out of the combustion chamber thereof a loss of power produced. To ease this problem of a crosscut area reducement we'll grind some material away at the sides of the valve steering an creating a more smooth profile curve of the exhaust port, Figure 5.

Figure 5

At this point, we're looking at something like as shown in Figure 6.

Figure 6

There can still be a lot done on these ports if I would've done a more thorough work on this head but I had to settle with this result and no further work was performed on the exhaust ports. If someone would want to perform further work it would be the face finish of the port walls and maybe enlarger the diameter of the port and perhaps bigger valves and the valve profile itself has improvement potential.

Now to the most important part of cylinder heads as it comes to flow, the intake ports!
The factory stock intake port is least to say quite small and in my opinion, they do not possess the optimal profile. Thereby we'll be going to machine this a bit and I'll do my best to describe what I've done and what my thought behind this was as I was doing it.

Figure 7, The stock intake port.

As seen in Figure 7, the intake port orifice is at an ovalized profile, 30mm by 34mm, and almost immediately reducing its dimensions to 26mm by 30mm creating a ledge, just like there is a small 26mm by 30mm port with a bigger orifice of 30mm by 34mm. This is not the profile curve I'm looking for at all, I want a smooth decreasing crosscut area of the port so that the airflow will experience a pressure increase as its approaching the cylinder because as we have a particular flow of air through the port and the area of the profile the air is flowing through is thereby forced to accelerate to uphold the mass flow built up. And this acceleration of air will result in a higher airspeed entering the cylinder and packaging as much air as possible in the very limited time it has before the valve closes and no air can no longer enter the cylinder.

Therefore we'll be going to evening the area decreases continuously as the air flow through the port, not in one step as the stock port does. And as we are doing this we'll end up with a port that is suddenly like a port that is 30mm by 34mm and with an orifice that has the same size as the port. Note that by doing this we've actually increased the ports dimensions by a whole 4mm in both(vertical and horizontal) directions. Remember that as the port will have its inlet orifice horizontal and it's outlet orifice vertical this will create a form of L-shape looking at the port from the side(front of the engine to back). This change of direction(from horizontal to vertical) will leave you a corner unless you use a radius to smoothen the shape out. And when it comes to gasses flowing through ports we want a nice radius that is not too small, since just like a pipe where you have a flow, the smaller the radius is the bigger resistance and loss of flow you'll end up with. As this mentioned you'll want to be careful with the machining of the "floor" in the port and rather be raising the "roof" hence this will leave you with a bigger radius of the port curve and less loss of flow, (Figure 8).

Figure 8, Intake port has been machined. Note that the cylinder head is placed upside down.

And we'll do the same with the intake ports as we did on the exhaust port towards the valve seat, we'll even the edges so that the crosscut profile of the port has an even transition to the valve seat(leaving no edges in the port towards the valve seat).
Figure 9 will show the result we have at this moment, looking down the ports from the combustion chamber.

Figure 9

This is where I settled with the porting and as mentioned there is a lot more work that can be done to this head then what I've brought up here. But this will perform a lot better than it did before the work.

I can almost hear your thoughts from here "but did it got any better, did the engine leave more power than before?" and unfortunately the answer is not that concrete hence I haven't any power curves or charts to prove this but I can really tell there is a lot more life under the hood nowadays. At this very day, I run the car with stock parts around the engine, stock intake manifold and exhaust system(heat shield to intake is removed and exhaust manifold shielded off the intake) with standard filter mount etc. And there is a lot more pull in the car, especially in the higher rpm band. It is a shame though that the speedometer only goes to 160km/h since I'm still accelerating.

Feel free to ask any questions.

Kind regards, Aron.
Nice work :D , since I will restore all my engine i am planning to do the same thing my self on my ma12 on the shop I work, I work as a mechanic (just know the basics I am still learning), do you have any warnings for me or something before I start?

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