Toyota MR2 Message Board - View Single Post - How to modify the 3vz-fe cylinder head (and others).

4v6 · 07-06-2009, 05:39 AM

Feather these into the seat insert and port as youve done with the rest of the bowl.

Now turn the head over ( prop it up on a length of timber if needs be) so the intake manifold face is pointing downwards.
The short side radius turn is next up.This is opposite the bowl that youve just blended in.
If you look at it, youll notice an apparent lip, almost an overhang where the factory tooling has cut into the port to produce the seating area for the insert, its the "arch" shape you can see on this port.

This sharp lip is detrimental ( very) to getting air into the cylinder because air dosent like to take sharp turns and when its moving at close to supersonic speeds as in a port it really dosent like to change direction because air has mass. Hang your hand out the car window at 80mph and feel the force.
The air coming off that lip creates vortexes and back eddys that make the stream turbulent which stops air further back up the intake from going where we want it.

When reshaping this turn we want to be making it aerodynamic, as in an aerofoil section of a wing, which is what the profile will resemble when we've finished on it.

Ive already done the hard work for you here and made a copy of the profile to aim for in 3D out of silicone rubber.
Compare it with the mould of the stock port on the right for the differences.
You need to try to copy the shape as closely as you can and use it to check the shape of the turn as you go.
This is one of the hardest parts of the job and itll take quite some time to get it just right but the payoff is way better flow with the valves in than youd get just by rounding that edge off.

Once youve carefully shaped the short side radius, you need to apply some efforts to the sides of the port walls where the SSR meets the vertical parts.
If you position the head on its end and look back up the intake from the valves, youll notice a "hump" type shape as the port wall makes the turn.
Its present on both outer and inner walls ( splitter side).
Youll need to be careful how you approach this bit of the job, what youre doing is making room for the air as it slows and goes around the SSR and blending the sides and SSR together, but not cutting into the already modified SSR.
In my case I transfer the head back and forth to the bench, test it, modify the area then retest to check the changes, takes ages.
Youre not going to be able to do that, so just aim to smooth and flatten that hump on both sides of the port, blending it in to the SSR at the apexes.
A gentle touch with a finger can usually detect what the eye dosent, so use that as a guide and stop when it feels smooth and flat.

Now youve done all these, turn your attention to the port divider/splitter.
The basic idea here is to slim the bluff nose of it down, reducing its width at the leading edge and smoothing the surfaces as it proceeds further into the port.
No need to knife edge it, just apply a small radius so its not dead sharp and dont work solely on one side, itll end up biasing the flow one way or the other which affects overall flow, again patience and care will see you right.
Use a pair of dividers to keep it central in the port by measuring.

You can see the basic shape to try and reproduce on the following photos of the port moulds.

Once youve completed all the major works in the ports you can start to apply a surface finish.
I use 80 grit sanding drums and 80 grit emery wrapped around a rod to further flatten and smooth the surfaces and impart a nice flow friendly surface.
Its best to run this at a moderate speed as too fast will just make it uncontrollable and the media wears faster.
You can use wd40 to help but I dont find it always necessary except in the chambers.
Start at the port mouth and work around the periphery, youll feel and see the effects of it almost immediately, continue that method all the way .
To get that cross hatch effect, stroke the tool back and forth covering the entire port, but be sure to not dwell in one area, keep it moving until youre satisfied with the results and you have a uniform finish.
This is what youll end up with.

In the chamber, use the sanding drum to carefully dress the surface and remove the myriad of pits and marks in the alloy.
Youre just aiming to remove sharp edges and blending surfaces.
Try to form smooth contours where the alloy runs down to the seats.
There are lots of edges in this part of the chamber and I use a homebrewed cutter to remove them evenly, but its possible to use old valves with the outer diameter reduced and the head ground with a bevel to protect the seats while youre working in the chamber with a sanding drum( its what I use).

Aim for a 120 grit finish in the chamber. You can go smoother but it takes a lot of effort and time and its likely not worth it.
Aim to get the ports and chambers as shown in the photos.

The exhaust ports are far simpler to work on believe it or not.
They too suffer from all the intakes casting flaws and can be improved quite markedly.
The 3vz fe has a compromised head design especially on the exhaust ports because theyre not identical across all three of them.
Two are of a "dog leg" design whereby one side of the port is a straight shot out with the other runner coming in at around 40 ish degrees and merging.
This creates turbulence and a loss.
All we can really do here is improve it so it flows better.
The "odd" port out on the end of the head is more of a siamesed design with almost equal length runners and this definitely flows better to the tune of around 10cfm over the other exhaust ports.
That kind of leads to a bit of a quandry.
Improve it or not?
Well yes, but bear in mind itll easily outflow the other exhausts if you apply the same measures to it as all the others.
I tend to develop the dog legged ports to flow equally and as highly as I can and then do that "straight shot" port last, balancing the airflow to match the others.
Takes time and effort.
All youll be able to do, is make them resemble each other as closely as possible and leave it at that.
I have it on great authority that balancing the exhaust flows isnt as critical so im happy to bow to much greater knowledge on that score.
Heres the 3vzfe's exhaust ports in silicone rubber, not a pretty sight.

Ok, proceed with the exhaust ports as per the intakes, removing casting lines and imperfections at the port exit (at the face and working inwards).
Theyre awkward to do due to their shape, but stick with it and youll get there.

The guide bosses are a fair size on these.
Reduce them as per the intakes, mostly on the widths and the "ramp" at the front of them leading to the guide, smoothing and blending them in.

Once youre happy with these, turn the head over and examine the bowl area ( under the valve head).

Youll notice some material just on and below the seat which needs removing and a rather large overhang.
I try to blend the overhang into the seat insert/ port but its pretty much impossible to remove it entirely as youd have to burrow into the material far deeper than really is good and its purely an aesthetic operation to remove it which you wont see when its all together anyway.
In this case, just smooth it as best as possible.
The sides of the ports at the divider have a similar "hump" to the intakes, so again its a case of basically flattening them and blending in to the rest of the port.

07-06-2009, 05:39 AM	#2 (permalink)
4v6 http://www.Typ-85.co.uk Join Date: Jun 2007 Posts: 184 Thanks: 2 Thanked 24 Times in 14 Posts iTrader Rating: (0/0% )	Feather these into the seat insert and port as youve done with the rest of the bowl. Now turn the head over ( prop it up on a length of timber if needs be) so the intake manifold face is pointing downwards. The short side radius turn is next up.This is opposite the bowl that youve just blended in. If you look at it, youll notice an apparent lip, almost an overhang where the factory tooling has cut into the port to produce the seating area for the insert, its the "arch" shape you can see on this port. This sharp lip is detrimental ( very) to getting air into the cylinder because air dosent like to take sharp turns and when its moving at close to supersonic speeds as in a port it really dosent like to change direction because air has mass. Hang your hand out the car window at 80mph and feel the force. The air coming off that lip creates vortexes and back eddys that make the stream turbulent which stops air further back up the intake from going where we want it. When reshaping this turn we want to be making it aerodynamic, as in an aerofoil section of a wing, which is what the profile will resemble when we've finished on it. Ive already done the hard work for you here and made a copy of the profile to aim for in 3D out of silicone rubber. Compare it with the mould of the stock port on the right for the differences. You need to try to copy the shape as closely as you can and use it to check the shape of the turn as you go. This is one of the hardest parts of the job and itll take quite some time to get it just right but the payoff is way better flow with the valves in than youd get just by rounding that edge off. Once youve carefully shaped the short side radius, you need to apply some efforts to the sides of the port walls where the SSR meets the vertical parts. If you position the head on its end and look back up the intake from the valves, youll notice a "hump" type shape as the port wall makes the turn. Its present on both outer and inner walls ( splitter side). Youll need to be careful how you approach this bit of the job, what youre doing is making room for the air as it slows and goes around the SSR and blending the sides and SSR together, but not cutting into the already modified SSR. In my case I transfer the head back and forth to the bench, test it, modify the area then retest to check the changes, takes ages. Youre not going to be able to do that, so just aim to smooth and flatten that hump on both sides of the port, blending it in to the SSR at the apexes. A gentle touch with a finger can usually detect what the eye dosent, so use that as a guide and stop when it feels smooth and flat. Now youve done all these, turn your attention to the port divider/splitter. The basic idea here is to slim the bluff nose of it down, reducing its width at the leading edge and smoothing the surfaces as it proceeds further into the port. No need to knife edge it, just apply a small radius so its not dead sharp and dont work solely on one side, itll end up biasing the flow one way or the other which affects overall flow, again patience and care will see you right. Use a pair of dividers to keep it central in the port by measuring. You can see the basic shape to try and reproduce on the following photos of the port moulds. Once youve completed all the major works in the ports you can start to apply a surface finish. I use 80 grit sanding drums and 80 grit emery wrapped around a rod to further flatten and smooth the surfaces and impart a nice flow friendly surface. Its best to run this at a moderate speed as too fast will just make it uncontrollable and the media wears faster. You can use wd40 to help but I dont find it always necessary except in the chambers. Start at the port mouth and work around the periphery, youll feel and see the effects of it almost immediately, continue that method all the way . To get that cross hatch effect, stroke the tool back and forth covering the entire port, but be sure to not dwell in one area, keep it moving until youre satisfied with the results and you have a uniform finish. This is what youll end up with. In the chamber, use the sanding drum to carefully dress the surface and remove the myriad of pits and marks in the alloy. Youre just aiming to remove sharp edges and blending surfaces. Try to form smooth contours where the alloy runs down to the seats. There are lots of edges in this part of the chamber and I use a homebrewed cutter to remove them evenly, but its possible to use old valves with the outer diameter reduced and the head ground with a bevel to protect the seats while youre working in the chamber with a sanding drum( its what I use). Aim for a 120 grit finish in the chamber. You can go smoother but it takes a lot of effort and time and its likely not worth it. Aim to get the ports and chambers as shown in the photos. The exhaust ports are far simpler to work on believe it or not. They too suffer from all the intakes casting flaws and can be improved quite markedly. The 3vz fe has a compromised head design especially on the exhaust ports because theyre not identical across all three of them. Two are of a "dog leg" design whereby one side of the port is a straight shot out with the other runner coming in at around 40 ish degrees and merging. This creates turbulence and a loss. All we can really do here is improve it so it flows better. The "odd" port out on the end of the head is more of a siamesed design with almost equal length runners and this definitely flows better to the tune of around 10cfm over the other exhaust ports. That kind of leads to a bit of a quandry. Improve it or not? Well yes, but bear in mind itll easily outflow the other exhausts if you apply the same measures to it as all the others. I tend to develop the dog legged ports to flow equally and as highly as I can and then do that "straight shot" port last, balancing the airflow to match the others. Takes time and effort. All youll be able to do, is make them resemble each other as closely as possible and leave it at that. I have it on great authority that balancing the exhaust flows isnt as critical so im happy to bow to much greater knowledge on that score. Heres the 3vzfe's exhaust ports in silicone rubber, not a pretty sight. Ok, proceed with the exhaust ports as per the intakes, removing casting lines and imperfections at the port exit (at the face and working inwards). Theyre awkward to do due to their shape, but stick with it and youll get there. The guide bosses are a fair size on these. Reduce them as per the intakes, mostly on the widths and the "ramp" at the front of them leading to the guide, smoothing and blending them in. Once youre happy with these, turn the head over and examine the bowl area ( under the valve head). Youll notice some material just on and below the seat which needs removing and a rather large overhang. I try to blend the overhang into the seat insert/ port but its pretty much impossible to remove it entirely as youd have to burrow into the material far deeper than really is good and its purely an aesthetic operation to remove it which you wont see when its all together anyway. In this case, just smooth it as best as possible. The sides of the ports at the divider have a similar "hump" to the intakes, so again its a case of basically flattening them and blending in to the rest of the port.