OST-013: Massaging a virgin ;)

[NoHachi]

Couple of questions for people in the know. But first a disclaimer: I'm asking this genuinely as someone who doesn't have the funds to send a head on a round trip to the US and have work done, but could take a risk on junking a 150euro replacement head in a diy effort. Since this thread has become an excellent primer on head work I thought that this would be a logical place for my questions:

@Oldskewltoy: Do you do before and after flow bench tests on your work? The reason I ask is because subtle browsing on the net has shown very unreliable results for modifications sometimes considered a "no brainer". I've seen ports lose flow after a mismatched seat was cleaned up. Enormous differences in flow based on which 3 angles you choose for your seat+valve and their widths.. all within a small band of variation. Etc..
Is there some kind of safe area where you don't pickup much flow, but don't risk on losing much of it either? Maybe there are some before and after results already on the net you could point me to?

@Bean Bandit:
In this pic (thanks for taking the time to show this):


What would be the method of choice to tackle this? Do you machine away that part of the valve seat in an attempt to blend? Wouldn't you risk ending up with a dead pocket in that location and a loss of velocity? Or do you epoxy/weld some material in?

In this pic:

The guides and guide bosses have been chamferred. I know from my old physics book that a circular cross section has an equivalent frontal area that is several times that of a teardrop shape. However it seems that the chamfer has been made in the opposite direction of what my physics book would suggest, with the tail pointing towards the direction of flow. Is there a reason for this? Are there any resources from which I could study this more?

Finally, I've seen ported MX5/miata engines from some great engine builders (Rebello, Sunbelt etc) pick up MASSIVE horsepower simply after porting the head and replacement of only the intake cam shaft. Otherwise some massaged stock manifolds and stock exhaust cam. Jumps from 110whp to 170whp. Does anyone on the boards here have any experience and software tooling to match a cam profile to head flow? In my Formula Student days I did some GTpower engine simulation, but getting a license for this kind of stuff is damned expensive. There are definite gains though and cam grinding is cheap.

[oldeskewltoy]

I can do flow testing... BUT that usually costs MUCH extra do to time required to set up and then remove, port a bit, and then re-set the flow bench. In fact flow testing a head is often the difference in a $750 porting cost, and a $7500 porting cost (as in the cost of an Atlantic head)

Concerning 3 angle (or in some cases multi angle) I do not have the machining equipment to do this, I have Loynings do these for me. I TRUST Loynings work, they are an active racing machine shop who have built many hundreds of 4AGE engines... as well as others. Loynings has 27 SCCA championships accredited to their work, they are the shop that ported my smallport head... with which I've planted 145whp and 112#/ft, also measured @ the wheels... that is also emissions friendly

The ports you are seeing are intake ports, so the un-tapered part is away from the air stream - tucked behind the valve. The area behind this is very small and is very disturbed air, by not tapering the back more I'm minimizing this and minimizing the disturned airflow behind the guide. Part of the tapered guides is to "follow" the minimized guide boss, since the guide boss is minimized, the flow up to the guide would be more disturbed if not tapered.

I have had my work checked on a flowbench - note the spec they are measured @ is 25", most flowbenches use 28". If you do the math, the intakes would flow @ 212cfm if measured @ 28"




Each head is different, you bring up the Miata head, 175whp is unheard of... the head is crappy, and the intake ports are to long horizontally, to make very good power in N/A form... the head is a big reason why most Miata guys go turbo because not a lot is achieved by porting a 1.6 BP head. The 4AGE head is better, and the old Ford Cosworth head even better then the 4AG head.

Interesting thread on Miata engines/builds - http://forum.miata.net/vb/showthread.php?t=365171

Concerning the 4AGE head, the key areas to port to gain power is on the exhaust side. The port and the bowls are decent, but some serious taper work allows the exhaust flow to merge at a better angle allow less turbulence, and superior flow. While the exhaust tends to be the "problem" with 4AG heads, the intakes can be bumped to flow significantly more overall as well.

Finally.... a point about flowbenches... they are very good @ measuring flow... BUT not as good @ measuring how an engine responds to this flow... the reason for this appears to be that an engine is not continuous flow, but actually is interrupted flow because of valve opening and closing events..... the flow bench can not measure these effects since it runs continuously.

[NoHachi]

oldeskewltoy Wrote:I can do flow testing... BUT that usually costs MUCH extra do to time required to set up and then remove, port a bit, and then re-set the flow bench. In fact flow testing a head is often the difference in a $750 porting cost, and a $7500 porting cost (as in the cost of an Atlantic head)

Concerning 3 angle (or in some cases multi angle) I do not have the machining equipment to do this, I have Loynings do these for me. I TRUST Loynings work, they are an active racing machine shop who have built many hundreds of 4AGE engines... as well as others. Loynings has 27 SCCA championships accredited to their work, they are the shop that ported my smallport head... with which I've planted 145whp and 112#/ft, also measured @ the wheels... that is also emissions friendly

I have no doubt that Loynings know what they are doing. Similarly I fully believe that its possible to reproduce port work on another head that you know has been proven to work on previous flow bench tests. I was just curious how you developed your ports since all the old scool guys with flow benches say that it is easier to ruin a modern head (ala 4AGE) then to improve on it. (just to be clear, I'm not insinuating you ruin a head, quite the opposite, hence the curious questions... I want to learn.)

oldeskewltoy Wrote:The ports you are seeing are intake ports, so the un-tapered part is away from the air stream - tucked behind the valve. The area behind this is very small and is very disturbed air, by not tapering the back more I'm minimizing this and minimizing the disturned airflow behind the guide. Part of the tapered guides is to "follow" the minimized guide boss, since the guide boss is minimized, the flow up to the guide would be more disturbed if not tapered.

This doesn't jive with the water drop shape idea, its actually the exact opposite. Many things happen inside a port so it probably isn't a straightforward thing. Do the Atlantic heads use similar profiles?

oldeskewltoy Wrote:I have had my work checked on a flowbench - note the spec they are measured @ is 25", most flowbenches use 28". If you do the math, the intakes would flow @ 212cfm if measured @ 28"
http://i79.photobucket.com/albums/j143/o...after2.jpg

That is a very nice result indeed.

oldeskewltoy Wrote:Each head is different, you bring up the Miata head, 175whp is unheard of... the head is crappy, and the intake ports are to long horizontally, to make very good power in N/A form... the head is a big reason why most Miata guys go turbo because not a lot is achieved by porting a 1.6 BP head. The 4AGE head is better, and the old Ford Cosworth head even better then the 4AG head.

Actually the later 99+ miata heads aren't as bad as their predecessors. They'll flow 200CFM at 28" out of the box. 140whp with only bolt-ons.
Spec Miata has seeded much development work. So reliable ported street engines sit at 165-170whp with mostly modified stock parts (all be it expensive Rebello street engines) and 7300rpm rev limits. Those built for higher rpm are far above that. What the pro miata builders have discovered after doing many spec customer engines is how to match their cam profiles to port shapes and vice versa. Which is quite interesting.

[Bean]

NoHachi Wrote:Couple of questions for people in the know. But first a disclaimer: I'm asking this genuinely as someone who doesn't have the funds to send a head on a round trip to the US and have work done, but could take a risk on junking a 150euro replacement head in a diy effort. Since this thread has become an excellent primer on head work I thought that this would be a logical place for my questions:

@Bean Bandit:
In this pic (thanks for taking the time to show this):


What would be the method of choice to tackle this? Do you machine away that part of the valve seat in an attempt to blend? Wouldn't you risk ending up with a dead pocket in that location and a loss of velocity? Or do you epoxy/weld some material in?

I tried the DIY effort myself on a spare bigport I have but as I am aiming closer to 200fwhp than 160fwhp a DIY job is pushing it (i.e. wilder cams/ more rpm would be needed for similar results) - to save my parts doing a round trip I sourced everything in the US so it only needs to go one way. Still it's not cheap but no serious build is and compared to prices charged in Switzerland I'm still saving a lot.

filling it would be ideal but it's an expensive thing to do and can go very wrong if not done properly. As you can see on the sliced head pic posted by Project D there usually is a bit of material under the valve seat itself which allows a bit of blending... everything not being a perpendicular wall in the stream helps. If you look at the picture from Dan with before and after view through the intake (the one with the red arrows) you can see the same area and how it's been blended. I guess on my head which is at Loynings this process was easier and smoother to do as new and bigger valveseats are used to accommodate the OS valves.

[oldeskewltoy]

NoHachi Wrote:

oldeskewltoy Wrote:I can do flow testing... BUT that usually costs MUCH extra do to time required to set up and then remove, port a bit, and then re-set the flow bench. In fact flow testing a head is often the difference in a $750 porting cost, and a $7500 porting cost (as in the cost of an Atlantic head)

Concerning 3 angle (or in some cases multi angle) I do not have the machining equipment to do this, I have Loynings do these for me. I TRUST Loynings work, they are an active racing machine shop who have built many hundreds of 4AGE engines... as well as others. Loynings has 27 SCCA championships accredited to their work, they are the shop that ported my smallport head... with which I've planted 145whp and 112#/ft, also measured @ the wheels... that is also emissions friendly

I have no doubt that Loynings know what they are doing. Similarly I fully believe that its possible to reproduce port work on another head that you know has been proven to work on previous flow bench tests. I was just curious how you developed your ports since all the old scool guys with flow benches say that it is easier to ruin a modern head (ala 4AGE) then to improve on it. (just to be clear, I'm not insinuating you ruin a head, quite the opposite, hence the curious questions... I want to learn.)

My secret.... isn't a secret @ all, I've studied a number of Loynings heads (ever heard of monkey see, monkey do?) I also DON'T promise I can match their work... because I can't. Just to be accurate, the 4AGE head is NOT as modern as some people would have you think. I promise a boost of 3hp to 10hp from my work (just to compare... my Loynings head makes 20+hp). All my work is taking a casting that is fair, and improving it - that is why I claim 3 to 10hp... some castings are that bad.

Finally, I've learned from a few friends that I have a talent when it comes to working with the equipment I use(mostly Dremel based). The owner of OST-007 is a close friend, and with all I was able to explain to him, he just couldn't operate the equipment with the same capability as I.

NoHachi Wrote:

oldeskewltoy Wrote:The ports you are seeing are intake ports, so the un-tapered part is away from the air stream - tucked behind the valve. The area behind this is very small and is very disturbed air, by not tapering the back more I'm minimizing this and minimizing the disturned airflow behind the guide. Part of the tapered guides is to "follow" the minimized guide boss, since the guide boss is minimized, the flow up to the guide would be more disturbed if not tapered.

This doesn't jive with the water drop shape idea, its actually the exact opposite. Many things happen inside a port so it probably isn't a straightforward thing. Do the Atlantic heads use similar profiles?

Hmmm, I use "drop tank" theory The large end of the drop tank is in the front - into the air stream. The back tapers to allow the air to flow smoothly past. Also placement of the guide in the bowl has something to do with it as well, some bowls (see link) are deeper than others, and allow the air to flow smoothly past(earlier in the radius). On a 4AG intake, the guide is very close to the bowls edge(later in the radius), the air is in mid transition from horizontal flow to a more vertical flow as it heads down to the valve

http://www.ws6transam.org/int_port_mod1.jpg - view showing guide in bowl center - early in the radius

Some Atlantic heads use very tapered guides, while others do have the guides removed. A significant difference in longevity(shorter) allows them to use techniques I can't use.

[oldeskewltoy]

NoHachi Wrote:(just to be clear, I'm not insinuating you ruin a head, quite the opposite, hence the curious questions... I want to learn.)

not taken wrong.... but it is GOOD to question because it often makes me re-think things. I've learned a great deal from many questions I'm asked because if I don't have an adequate answer, I can quiz the guys @ Loynings and get the lowdown from their experience.... monkey does a bit more than see :wink:

[Bean]

oldeskewltoy Wrote:

NoHachi Wrote:(just to be clear, I'm not insinuating you ruin a head, quite the opposite, hence the curious questions... I want to learn.)

not taken wrong.... but it is GOOD to question because it often makes me re-think things. I've learned a great deal from many questions I'm asked because if I don't have an adequate answer, I can quiz the guys @ Loynings and get the lowdown from their experience.... monkey does a bit more than see :wink:

Hope my loyning head will help you as a learning source aswell

[oldeskewltoy]

Bean Bandit Wrote:

oldeskewltoy Wrote:

NoHachi Wrote:(just to be clear, I'm not insinuating you ruin a head, quite the opposite, hence the curious questions... I want to learn.)

not taken wrong.... but it is GOOD to question because it often makes me re-think things. I've learned a great deal from many questions I'm asked because if I don't have an adequate answer, I can quiz the guys @ Loynings and get the lowdown from their experience.... monkey does a bit more than see :wink:

Hope my loyning head will help you as a learning source aswell

I have EVERY intention of checking out what they will be doing... but as you said, their work will be sibstantially different... because of the O/S valves, and the work that entails

[oldeskewltoy]

Its been in the mid to upper 90s(f) here, I haven't had a lot of time to do more work, but I was able to do this.........

Here is something you just don't get to see everyday... What you see below is a cropped together photo using the gasket as a guide. What is shown here is ports #1 and #4, taken at similar angles, with one view mirror image to match the other view. Finally, the views were split and swapped to show what I actually do on the exhaust ports

It shows quite a story, can you (all readers) describe what you see? What can you see... besides one upper, and one lower is shiney

[Project D]

port matching with the exhaust gasket, clean the mismatched seat and removed all the casting I presume