'99 Mustang build

BRN2RUN

Active Member
Well, I obviously have a bit more money than brains. :) I decided to buy a set of remanufactured 3.8 heads (new valve seals, valve guides, crack/ pressure tested, valves re-done, milled surface, etc) and work on another ported head design. I could have just taken some off a car at the wreckers, but I wanted a fresh, clean slate to work with that may not potentially have valve seat pitting and worn valve guides and seals, or whatnot.

I decided against the SC engine swap, and ruled out the Mark VIII swap. In the case of the SC swap, I don't think that I want the threat of two cars being under the threat of head gasket failures (even with MLS gasket upgrades and ARP bolts). Plus, although there's a good presence, online, for used parts, the fact remains that (aside from the oil filter, coil pack or accessory belt), it's a bitch to find parts in an emergency, ie: walking up to the auto parts counter and buying something. PCV valve is SC specific, too, etc. Even at the parts store, everything is a couple of days away, unless something is air freighted in. My worry is that--as the Stang is a winter driven car and literally is a year round driver (and the SC is stored in the winter, meaning that in the winter, I don't have the luxury of just stepping in the other car in case of repairs)--that I need something as common as possible, and everything that I've needed for the Mustang has been available at the parts counter, immediately. And there's always usually two or three base 3.8 Mustangs at the wreckers at any given time. Finding an SC is near impossible to find.

The Mark VIII's, after the intake/ tune/ bolt ons just don't make as much power as they should. Some major cam/ head work needs to be done to get it to be on par with the Cobra engine. Thought of dropping a Coyote engine in the car, but the engine would be worth way more than the car, itself, and if the car got written off, the engine's value would go way down (it's tough haggling with the insurance company). A GT engine swap would be cool, too, but really, compared to the modern engines, they're pretty slow, too, in an automatic car. GT's of this era usually don't go for very much more than the 3.8's here (depending on vert vs coupe, mileage, colour of the car, etc), which would be a good deal if one were to buy one, but at this point, an engine swap would cost more than the car would end up being worth, especially as the miles pile up on a daily driver car. Even though my engine is at 205,000 kms, it makes more sense just to drive it until the engine gives out and then figure out what to do at that point. A 16 year old car is still a 16 year old car, even if it has a lower mileage engine dropped in it.

So that leaves me with the original factory 3.8, and I dunno......I just think that there's something cool about having a numbers matching car, and working with the deficiencies of that era's designs (like someone maintaining a carbed setup, instead of moving to an EFI system). I think that there's something cool about the split port engine, even if it doesn't make that much power.

In my previous head design (http://www.v6mustang.com/threads/my-current-build-head-work-etc.278414/), it is true about what they say--they end up being practice heads. :) While almost all of the things that I did, I would continue to stand by, there's a few things that I will now do differently, to improve power and reliability:

1. valve guides: I think that I ground them down too much. In a race car only application, I think that this would be fine (and would undoubtedly flow more CFM), the weakened support would likely be a detriment at higher valve lifts on a custom camshaft. Maybe not. But on a daily driver car, I'm doing things for reliability, instead of all out power. In the next design, I will taper them down from the valves, which should improve flow, but still retain the strength of the stock valve guides

2. too much material removed from combustion chamber: I don't think it's a huge issue, as static compression really isn't worth tons of power, but I think that there's a tad too much removed, and the sides of the combustion chamber had too much material removed in that it's too close to the gasket edge. The spark plug boss would end up being less shrouded, but I'm now worried if too much material may have been removed and would weaken that area. I will now just smooth out some rough casting spots, and any sharp edges.

3. too much material removed from intake bowl: seeing as that they were ported and polished when I bought them (likely a DIY home job) that were done pretty well, whoever had done them had filed down a lot of the first valve seat angle that transitions from the bowl to the valve seat area. I think that this would slow down velocity at low to mid lift quite a bit on a stock or mild cam, and might make up for it at higher lifts, but that's also not where these engines spend the bulk of their time at

4. re-evaluate exhaust port: it's a small valve/ port, which builds up lots of low end torque, but I'm going to go over some exhaust port designs in other types of engines with smaller ports/ valves, to see what works for them. Headers/ shorties don't improve power much, likely because of the small size of the exhaust port/ valve, but if some additional CFM can be gained without hogging things out too much, and keeping up velocity (but at some higher RPM's and maybe helping to contribute to a higher torque peak and a more gradual torque peak), that would be great. I don't want to lose too much torque, but I'd like something that isn't too peak-y, either, because the weak 2nd gear ratio in the 4R70W just feels so much slower when it's out of the torque powerband when it shifts from 1st to 2nd and drops to 4000 rpm in my car, and not having that gear multiplication mask the engine's lack of breathing at those RPM's. Even 4.10's still feel slow when it hits 2nd gear, but in the lighter car with heavy wheels (56 lbs apiece--112 lbs total rotational weight versus about 80-83 lbs in stock 15" wheel form with 205/60/15's) versus the SC (with 3.27's and an AOD), at cruise speeds (when the SC isn't in boost, or is at low boost at 1-3 psi), the Mustang feels much quicker on the butt dyno, and the throttle is way touchier than the SC.

5. lapping the valves: buying a set of reconditioned heads seems to make more sense, since lapping the valves (according to some experts) doesn't provide the longevity that re-doing/ replacing the valve seats will. Again, out of longevity concerns, this seems to make more sense.
 
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BRN2RUN

Active Member
I've spent a ton of time on a new reconditioned set of heads, and it was great to get a clean slate with an as cast factory reconditioned set of heads, instead of working with an already ported set. Until I flow bench this set and mill them for a compression increase at maybe 9.5-9.8:1 and put them on the car, everything that I'm doing is hypothetical at this point (ie: no pictures), but I will say that i've flowed them using a vacuum with a light thread/ string run through the ports to see where the majority of the airflow is at varying valve lifts, and I had also put some aluminum shavings on various sides of the port, to see where a vacuum draws the air resources from, and I can safely say that in the intake ports, the port floors flow the majority of the air (short side radius), the top flows a bit, and the sides flow next to nothing in comparison. Most of the effective porting work seems to result in directing the airflow towards the short side radius (a good half of the intake valve seems to flow really well from the two ports merging their high velocity into the short side radius, just based on how quickly a string/ thread will circle the outer diameter of the valve), but the downside is that there's only so much air that you can flow through that area. That's why I think that these engines are so tough to get the high end out of--and why flow bench data is somewhat irrelevant--just because the air is so lazy on all the other areas of the port, and that the majority of the CFM numbers are what you can physically cram through the short side entry.

I'm going to try a couple of different port designs and do some more string/ thread flow testing and see what happens.
 

6 Shooter

Well-Known Member
Just a precaution--Milling the heads down to increase compression will cause problems with the lower intake fitting correctly against the heads and lower manifold gasket. The holes in the lower intake manifold will not align correctly with the holes in the heads and the angle between the heads and lower intake changes as well. Milling just 10 thousands is OK. Twenty, maybe. Thirty and hole alignment and angular difference begins to be a real problem with gasket sealing.
 

BRN2RUN

Active Member
Thanks for the info! I believe that the FelPro headgaskets that I had bought had said to mill the heads 10 thousandths to compensate for the gasket thickness, but I will be wary of doing much more than that.
 

BRN2RUN

Active Member
The short: I think that there's additional power to be found in these heads. Hopefully i've found it.

The long (and incredibly long at that, don't say I didn't warn 'ya, heh heh), because I've spent a ton of time porting and doing some actual R&D on it: Man, I feel like a brand new human being or something. :) The vacuum/ string theory I'd came across at this website below:

http://www.diyporting.com/thread.html

Indeed, it does impart more actual useable flow data than even a flow bench could perhaps tell you. Flow data is great, but if you don't know where exactly the heads are flowing, it's possible to have great flow data on a bench, but lower than expected dyno/ road performance numbers in that quality flow isn't necessarily there. What i've found through an almost finished pair of heads (non-polished) with a makeshift velocity tube of the same relative size as the exhaust gasket openings (plastic cylinder that is see through) with a vacuum and string hooked up to it, and with an exhaust port design that leaves the sides alone (there is not as much flow on the sides), and with the short side opened up and the port roof opened up, at a high valve lift, on the long side/ port roof, what happens is that the majority of the airflow bounces off the first valve seat angle off of the seat and straightens itself out to flow through the majority of the center of the port. This is where the factory multi-seat angles really pay off.

What I can determine, so far, is that port roof porting to an appropriate angle on the short side not only improves the short side flow, but also to straighten out port roof flow at higher valve lifts. Right now, I can't really tell what happens at low valve lifts (ie: the valve is in the way of sight, though I can peer through the port a bit from the exit angle), but i'm assuming that port roof modifications along the valve guide/ boss will help pick up some flow, though not much. And the valve stem is a huge hindrance in the straightness of that flow. Also, the ridge that is along the port roof, it may scream "remove this", but I believe that it is there to fight reversion at low valve lifts. I don't have the luxury of seeing other people's ported bowls, but if that ridge is removed (which would also take the exhaust bowl to a size slightly larger than the valve seats, I suspect that may be a partial reason as to why many of the ported examples don't make as much power as they should. Removing that ridge likely reduces velocity on the port roof, and invites exhaust gases back into the combustion chamber. Similarly, there's also a step that's a mm or so right below the short side radius, on the last angle of the valve seat area. It's tempting to remove it, but I'd leave this alone, because it likely is also helping to fight reversion. Some guys may blend this in, but air in the forward direction skips right over it because of the steep "cliff" of the exhaust port, and when air is trying to make its way back into the engine. On its way back, it's going to hit that step on lower valve lifts.

I'd hooked something I call the "Combustinator" up on the combustion side (really, it is just a Slurpee cup modified to have the same bore as our 3.8 :) but with a variable part in it that can be moved up and down with a vacuum attachment to simulate some pumping motion and with the intake valve closed and at low valve lift to simulate some overlap). It may sound hilarious, but a large Slurpee cup with a hole cut out in the end for a vacuum attachment provides a lot of suction with a spark plug in the chamber (t will pull the sides of the cup in when the intake valve is closed), and you can move the attachment around in there to vary the angle of vacuum and the closeness of the vacuum to simulate a moving piston. The reverse flow is non-existent at low valve lifts, and is very lazy at mid to higher ones, and the reverse flow that does exist is mostly on the short side radius and there appears that there is nothing that can be done about this, since the ports, despite their size, are incredibly efficient in their design, and I think that it's inevitable that some of the tradeoff for the outstanding flow on the one side will result in a tradeoff of some reversed flow. For example, i'd intentionally left a spark plug out of the chamber, to see if it would draw much resources through there. It did--way more than through the exhaust port with the velocity tube (ie: simulation of a header/ manifold pipe). I have BBK shorties on my car, and the gains aren't really there, but this exhaust port design should keep up the velocity, with some added flow.

The Super Coupe heads, for example, i've done the same analysis and the SC ports are huge, but they lose an incredible amount of the velocity of the split ports. The split ports have tremendous velocity on the short side, whereas the SC ones do not. It's nearly impossible to keep the valve closed by hand on the split ports with a vacuum/ velocity tube hooked up at lower lifts, whereas on the SC heads, it's relatively easy to keep the valve open. With the velocity tube, no matter which angle I placed it at or how far away it was, the majority of the airflow on the split ports is on the short side radius, and the tuliped shape valve is a great design. I think that there's still benefit to doing the long side/ port roof, as the scavenging effect of the exhaust, as well as the piston moving things through at an extremely high pressure will force things out each side of the port.

With the exhaust port, I believe that its shape is a problem. It otherwise fights way higher than its weight class, due to the great velocity that it has, and the multi-angle valve seat angles. It has a slight bias towards one side, and as mentioned, the sides don't flow as much, and the port roof flows some air, though with not as much velocity as the short side. Trying to straighten out the port will reduce the velocity without really giving the right gains. The answer there, I think, is to port the short side/ floor heavily to give it the steep slope but give the middle section a bit more room and drop it off with a slightly beveled edge. As far as the exhaust port exit is concerned, there's debate as to what is the proper sizing--gasket match or not? The theory is that leaving a step helps to fight reversion, but since the reverse flow that i've observed from hooking up a vacuum in reverse, the reverse flow is only at very high lifts, is very lazy, and comes from the center of the tube towards the short side, rather than on any of the sides of the port. Opening the port floor and port roof almost up to the gasket (minus 2 mm or so) and leaving the port sides yields a lot of flow, but I can say with all certainty that the reverse flow is still minimized. You have to open the valve up to at least 1mm or so before it starts pulling the string back through the tube/ valve, but even at that, the velocity of the reverse flow isn't nearly as much. For example, it's difficult/ impossible to keep the valve closed at lower lifts, by hand, when the vacuum is pulling through the port in the normal way with a velocity tube, but the cylinder area is so much larger in comparison (even when the vacuum source is extremely close), that the tradeoff in flow improvements on the short side radius are worth doing, because the ratio of any forward flow to reverse flow is going to be there, just based on the shape of the short side "cliff" velocity.

Of course, there's no real way to measure the actual vacuum dynamics inside of the engine, but under pressure, the laws of air physics do not follow a set of rules, as the center of the vacuum/ pressure and resulting swirl happens. When I hooked the Combustinator up to the intake side, the airflow went in wacky directions that I had no idea that they travelled in. Varying the amount of vacuum/ location of the source, sometimes the air went in a completely opposite direction than I thought it would. Still using a string, what happens is when you only introduce a small section of string (airwave being shorter and lighter / string is lighter?), it tends to want to follow a certain path, but when you let more string go (airwave is heavier/ string is heavier and takes the new path of least resistance?) it takes on a different path yet again. This is where port shape on the sides appears to affect the string/ air's ability to be able to cycle between its paths of least resistance at varying vacuums/ valve lifts.

At least half of the intake valve flows really well on these heads, and the shape of the sides of the port when entering the bowl, really assist in directing airflow around that half of the valve.
 
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BRN2RUN

Active Member
There are many myths that surround head porting, but some of them are rooted in the carbed days, and unfortunately, there is very little actual information for the most effective porting out there on our heads. I've always wondered why some people have got H/C/I done by some professionals, only to see 210-220 rwhp with a cam. There should be more power to be had, especially given the split ports and the multi angle valve seat job from the factory. It's bugged me, and it has bugged many others, too. You can take or leave this information, but it is the most comprehensive that I can offer. So here goes:

After doing quite a bit more vacuum/ string testing, I can say that Ford did a great job on their design of these heads. They put a lot of thought into them. While the valves are shrouded in the combustion chamber to a certain extent, the interesting thing is that the sharp angle of the combustion chamber on the bottom side (long side/ port roof) and chamber wall side of the exhaust valve, deflects onto and at the exact angle of the second valve seat angle. The third valve seat angle assists greatly of the flow out of the port floor (long side) and sides on higher valve lifts, into the fastest way out of the port.

My synopsis of the intake is that there's not really a whole lot that needs improvement, or better yet, that can be done that isn't already there. After gasket matching the ports, there should be some gains to be had with a gasket matched intake, because of the availability of additional air resources, as long as the gasket match is about an inch or so into the port. If I were to do another set of heads, I may even only gasket match about half of the port (the floor and left hand side of the port, when looking at it as it would be installed on the car). Those are the sides that flow the most, and the most quality airflow with the straightest air path. On the low end torque runner port, what happens on the left hand side of the port entry, is that it skips basically entirely over that curve that is a few inches of length into the port, and bounces off the first wall of when the port when it goes around the bend to accelerate itself, and angles itself down into the short side. The high RPM port/ runner (the round one) is much more effective, as it is much straighter, and the air flows off of the sides of the port with good velocity when it needs to draw additional air resources towards the short side entry into the bowl area.

One half of the intake side ports (both the short and long runners) flows really well and the other side is a low pressure one and/ or with turbulence (ie: the pocket coming right out of and after the injector) is a low pressure area and a turbulent one when it picks up velocity. The bowl pocket on the long side of the high RPM port is a low pressure zone. I had sucked some aluminum shavings into the port to see where things were going, and some had got hung up in that low pressure zone. If one were to put some additional metal in there, it could definetely increase flow on the intake side, by being high enough to direct some air resources towards the long side of the bowl. Although, I wonder if this wasn't intentional by Ford, to slow air up on that side so that it can mix better with the fuel as it enters into the bowl. The long side runner entrance into the bowl definetely is a higher velocity area without that low pressure air pocket. I can't really see exactly what's going on around the seats/ short side on low lifts, about a mm to 1.5 mm, but I can say that only about a third of the intake's port has any velocity or pull, so the bowl shape/ blending the final angle of the seats into the bowl helps flow. Knife edging the split port merge area (as many do), only assists in transitioning the higher flowing side wall of the port, to assisting quality flow out the short side of the port into the bowl area.

The exhaust, I think that the biggest impediment to flow is not the valve guide or valve boss area, is the valve stem. On the bottom shrouded part of the combustion chamber around the exhaust valve, the angle of the air deflects off of the second valve seat angle (as previously mentioned), but a modification that could (and should--I will be doing this) likely really help flow, is to taper the valve stem a small bit, because on the bottom long side of the valve, airflow at high lifts doesn't get anywhere near the valve guide. The genius is that Ford used the sharp edge of the shrouding to straighten the air on the side of the valve that otherwise doesn't flow well. It tries to go straight through the port, and the valve stem is the biggest impediment. The airflow on the lazier port roof/ long side in this case is straight, high velocity, and with little turbulence. 'Ya gotta love that. :)

That weird edge on the long side that looks like it's the first contender to be removed for more power--I've confirmed what I had originally thought: if your heads have this ridge removed, whoever ported your heads (with stock valves, at least) screwed up. Go and demand your money back :), because although these exhaust valves are small, they're effective. Unless the porting guy can explain it to you in these terms, they don't know why they removed it, other than that removing it yields more gains on the bench. The Super Coupe heads, for example, look like the bowls are full of weird, sharp casting lines that make no sense, but the issue with taking those lines out is that it's a low pressure zone that yields no real world gains (if not losses-though it will look better on a flow bench), but will introduce a ton of reversion back into the heads; killing power.

I can say this, since the other heads that I worked on, I had ruined them. They looked great, but after I had flowed them, they were disappointing. I removed too much material from the cross section of the port, and I had removed the ridge in the exhaust bowl, and had taken the combustion chamber shrouding on the long/ port roof side, and what ended up happening is that the airflow slowed down in velocity in a big way out of the sides of the exhaust ports. I didn't put the heads on my car, but there was no need to--at lower RPM's, they would have lost a lot of power and it would have needed a big cam to push enough air through. When I de-shrouded the exhaust valve on the port roof side in the combustion chamber, what ended up happening is that the airflow on that side that is coming from the chamber wall, bounced off the main valve seat and directed itself lower into the port, closer towards the valve guide area, which then bounced off the valve guide with more turbulence and way less of a straighter flow. So be careful when doing combustion chamber work--deshrouding in the wrong place has the unintended consequence of an otherwise helpful ping-pong effect to guide the airflow out the center of the port.

If you think you're not making enough power, check the bowls and see. If that ridge is gone, you'd gave up a lot of high and mid level valve lift for whatever low lift gains there would be (and based on the airflow on these heads, extremely low valve lift isn't very much, because it's limited by the port shaping). And there is likely a lot of exhaust reversion back into the combustion chamber because of it, as well. The reason for this, is that after tons of actual airflow and directional airflow testing (and not a flow bench), is that this ridge helps steer air velocity towards the short side of the port, and if the exhaust ports were opened up while removing it, you had gained flow on the flow bench, but lost tons of velocity. On the combustion chamber wall side on the exhaust port, you'll notice that the exhaust bowl ridge has a more pronounced ridge, that leads to a sharp point. This sharp point takes a low pressure area and speeds it up so that it skips entirely almost over the exhaust bowl side that flows the least. The exhaust port bowl side that is coming off the center of the combustion chamber has a smaller ridge, but the reasoning is because that side already flows well. Based on the airflow directionality at mid to high lifts, the most crucial angle to additional flow, as mentioned, is that combustion chamber edge bouncing off the second valve seat angle. You're otherwise only getting roughly a quarter of an exhaust valve that has any real velocity (the quarter that is closest on the short side, towards the spark plug).

The exhaust port is way more fun to work on, just due to all the creative and interesting angles that Ford had gave it, just due to it being a comparatively smaller area. The rest of us just have to interpret their creative angling and work with it, instead of removing things.
 
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6 Shooter

Well-Known Member
Got to looking for some photos the other day and found these, which relate to your discussions about head porting. Forgot about them. Hope this head porting shows what was done. The olive drab color is ceramic coating. The intake is not coated. The exhaust port is coated.


 

BRN2RUN

Active Member
Those look great! Looks like they knife edged the split ports at the bowl. I can't really see the edge of the exhaust bowl that well, so I don't know if they had removed that ridge or not.
 

BRN2RUN

Active Member
I've finally finished my heads (don't want to even say how many hours it took ;)), but probably in the first week of January, I'm going to get each intake port/ exhaust port flow benched and will mill the heads no more than what Six Shooter mentioned. I'm thrilled that someone around here had a flow bench, because I wasn't sure if anyone did. You can't totally go on flow bench data, but i'm just looking for a ballpark figure of what the heads flow as an overall reference, and also something to factor in when getting a custom cam ground for my setup. It will also be nice to provide for others, to see what gains can be had with perhaps a somewhat different head design than some other ones.
 

6 Shooter

Well-Known Member
Can't believe how far back in time this was, but in Nov 2011, did some bench flowing of a head and the new Freestar intake. Here is the results of the head flow without the intake. The column of numbers on the right must be multiplied by 3 to get the number. The column of numbers on the left were (I think) RPMs in thousands. Ideally, the best numbers based on the redline of the motor would be close to 300 at 7000 rpms. Just do not recall if the head tested was one of my ported heads. Not likely as they were probably being ceramic coated during this buildup process. But we were trying to get baseline numbers, so it did not really matter if it was a stock head or not, at the time.


Photo shows my stock Freestar intake before cleanup and porting.


My Freestar lower intake manifold after porting and modifications for coolant flow. The ported lower intake is also bolted to the same head bench flowed earlier. The goal was to see IF the addition of the intake increased or decreased the flow of heads while bolted to the heads. Will say that to everyone who observed amazement, the flow numbers increased by about 10 vs stock numbers posted above. So, 270 became 280 with the Freestar lower intake manifold attached. In way too many cases, the flow numbers of the heads will drop after attaching the intake.


We than added some clay around one of the holes to see if the flow of the heads numbers improved, which they did a little more. This was my proof of concept about whether a Freestar intake would be an improvement over a ported stock 3.8L lower intake. This photo should have been #2 above instead of #4 show here.
 

BRN2RUN

Active Member
That's awesome! Do you still have it on your car? What did you do for the upper intake part? Did you use your custom box?

270 cfm is a great accomplishment. I'm hoping for 250 or so CFM on a stock valve configuration. SSM's stage 3 heads flow 260 on the intake side. The Freestar intake seems like it would draw air resources quicker than with the stock Mustang intake, since the opening into the lower intake ports have less of a defined runner. The upper RPM ports have a nice, unimpeded shot to the bowl area, whereas the low end torque runner has a lot of length, which should be great for low end torque, but not as good for upper end horsepower, since the air has all the way to travel back through the runner when it hits the back of the intake valve. I guess that's a similar concept as to why the GM TPI engines make such great torque, but not that much higher RPM horsepower......the air wave/ pulse has that much further to travel back down the runner.
 

6 Shooter

Well-Known Member
Yes, the Freestar lower intake manifold is still on the car. Throughout all the various ideas and setups. the twin turbos do not have any turbo lag, and pull like a bull. Even with the street tune, the acceleration is wicked. Even with the 10.5" rims, the wheels will spin a little when the full boost occurs somewhere around 3000 RPMs. Things happen real fast when hitting the gas and I do not have a Go-Pro camera to watch all that is going on.

And yes, am still using the custom box upper which all fits under the stock Mustang hood, even with a 3/8" phenolic spacer to reduce intake heat.
This is the inside of the air box. Bottom plate attached to the Freestar lower intake.


Air box upper intake fabricating.




Check this out. Quite interesting. Notice the part about intake/head porting and velocity. http://www.enginelabs.com/engine-te...ustom-inline-six-dragster-engine-turns-heads/
 

BRN2RUN

Active Member
Thanks for your ongoing help and advice! That is one of the best custom intake manifolds that i've seen--any car, any setup.

Those velocity stacks would give some serious power on a FI engine. I've pondered the lower intake manifold on my Thunderbird, as well.....the problem is that it's crammed in there pretty tight, and the ports in them don't allow for much modification....some of the ports do, but other ports would be a problem, since they have a solid wall of metal right beside them. The biggest enemy is even distribution between the cylinders, and the threat of going lean.

I've been mulling over some design ideas on the short side radius in the heads. Flow testing/ directional testing still proves that the short side flows the most amount of air on these heads, and that the high and low rpm runners both have the most flow/ velocity on the short side. The question really is how much turbulence is induced by opening up that area too wide, where you're getting too much air bouncing off of the back of the valve and disrupting the quality airflow. It looks like Ford made the flow pretty straight at the factory.
 

BRN2RUN

Active Member
Either today or tomorrow, I should have pictures of the thread/ flow testing, with the "Combustinator". It's really, really difficult to ever get the thread to flow on anything but the short side, and it's those two "cliffs" that drop off from the two ports that create a ton of velocity. It was pretty difficult to get some pictures because of having to hold the vacuum, camera and keep the threaded wands straight through both ports, but i'd snapped a ton of pictures in motion that best represent each port, with the vacuum source at varying points in the simulated combustion chamber. The two threads from each port didn't cross paths that much, which would indicate that the port job that i've done would keep the two ports flowing pretty well with a minimum of turbulence. I'd put a spark plug in the chamber and taped off the injector port area to keep the vacuum as high as possible.

At higher valve lifts, the low end torque port goes wildly turbulent in the combustion chamber, though it is the more likely of the two ports to utilize the bowl area on the long side (there is a pressure recovery area on the long side from the factory, right before the valve seats). The upper end port will pretty much go wherever the vacuum source is, and I'd assume that the swirl motion within the cylinder would have a good effect on the upper rpm port as a result. The upper rpm port also is the most susceptible to valve size and shape, as the flow is very straight and generally hits the edges of the bottom of the valve. Oddly enough, though the lower rpm port flows oddly and somewhat randomly, almost, at higher valve lifts, it seems to be the port that induces its own swirl (regardless of where the vacuum source in the combustion chamber), which is probably a good thing, since that is the port that the fuel is going through.

The tough thing to tell is the mixture/ swirl patterns in an actual running engine, and how much of it is a good thing, and how much of it interferes with the straighter airflow coming out of the upper rpm port.
 

6 Shooter

Well-Known Member
It is not all that evident in the pictures, but the Freestar lower intake actually has one runner in each hole that is about 1/3 shorter than the other hole. The other thought at the time was that the supercharger or turbos would be cramming air in the cylinders any time that the valve is open, so was not all that worried about turbulence or velocity. Very interesting what you find on bench flowing, strings, and changing port and bowl shapes. Really have no clue on how to do that type of porting. As the video link posted indicates, there needs to be a lot of trial and error bench flowing and temporary port and bowl changing to get the most out of a set of heads. Too often, many do the heads and stop there. What I was trying to show/indicate is that adding an intake or an exhaust to a set of heads can increase or decrease performance and it takes quite lot of experimenting and research to find the best what works best.
 

BRN2RUN

Active Member
I'm taking the heads in to be milled/ pressure checked/ seats checked and flow tested tomorrow! Very excited, but also a bit nervous, because this is where some real official data starts happening. And of course, my heads last year that I had done, there were some errors on them, so the real R&D time in these is astronomical. As per Six Shooter's suggestion, I'm milling conservatively......the heads were milled .003 when I got them (reconditioned) and I'll mill them .015 or so (FelPro recommends to mill them .010 to compensate for their thicker gasket, so the actual real milled surface will be .008 above anything compensating for the thicker gasket).

Anything else that anyone thinks that I should know or to look out for?
 

BRN2RUN

Active Member
Update: I had dropped my heads off with a local machinist who came recommended to me. They may take until early-mid February, as he's backed up, getting married, and wants to be able to flow test each port on the same day, as he finds that as temperatures change, the results do as well. So we'll have to wait and see. I had done a couple more revisions to the overall design that should improve flow in lower flowing areas of the head, but without hurting velocity by keeping the characteristics of the heads that don't need much massaging.
 

davidcseifert

that V6 guy
Hey 6 shooter, would you make another one of those nice upper intakes for the 6-12 lower intake? I have a stock lower for one here i'm thinking about having ported for my car.
 
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