The Secret Behind: "Ford's New Super Cobra Jet!"
Ford's new SCJ cylinder head
When Root Industries approached us about creating a new 429-460 cylinder head to upgrade the A-429 aluminum CJ head, we knew it would be a monumental task. In the 1980's we helped design the A-429 CJ, which has turned out to be one of Ford Motorsports' most successful products. (At least 19,000 sold.) We had to make this new head achieve enough improvement to warrant the existing CJ owners to want to upgrade.
Our self-imposed rules:
Original intake and exhaust port size and location
Original bolt patterns, intake and exhaust
Original valve cover height and bolt pattern
Original valve diameter and length
Original chamber size (72 CC)
One of the first challenges we faced was resisting the temptation to raise the exhaust ports. By doing so, this would have canceled out millions of vehicles for which these heads were intended. Re-focusing the way we went about designing this new head was a little unconventional, but in the end, the results were worthwhile. We started with Ford Motorsports 514-crate motor, sent to us by way of Ed Lyons. Initial dyno testing was superb, as it came in the door with a best of 645 HP. Ford rates them at 600HP, but they've learned to under-rate things so that if they are dyno checked, they won't fall below expectations. During the course of testing we would pull one plug wire off at a time and make a dyno run. We mapped out the engine to see what the power levels were on each cylinder, and then we pulled one head and worked on only one cylinder. We didn't want to waste time on all eight until we had the modifications perfected and were absolutely sure this is what we wanted. After re-configuring the cylinder and testing it, we had picked up about 10 HP on the newly modified cylinder, with the whole engine gaining 10 HP overall. Now the real work began. For some unexplained reason, it takes 20 times longer to do eight cylinders than one!
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Exhaust port SCJ (left) has much more gradual turns and a smoother casting. Notice the short turn height difference. |
What Is Different?
Until you know what to look for, the new SCJ heads might seem like a tune-up of the existing heads. It is not supposed to be a secret, but most people don't know the huge changes we've made.
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The exhaust port length difference is apparent, in the SCJ on the right. |
The current thinking on racing cylinder heads would be as follows:
The intake valve should be as far from the cylinder wall as possible.
The exhaust valve should be as close to the cylinder wall as practical, without hurting the flow. This makes room for the intake valve, which was moved toward the exhaust.
The intake valve should be as close to the exhaust as possible without scraping, leaving no room for larger valve diameters. Again this is for maximum bore clearance.
The intake valve wedge angle should be flattened out to 8 degrees. This has several benefits: The long side, or spark plug side of the valve won't be an obstruction to line of sight airflow. The long side of the valve will sit higher in the chamber, making it easier to achieve a small chamber. The piston's valve pocket won't need to be as deep, resulting in a stronger piston with higher ring placement.
The intake valve location should be moved not only away from the bore, but also towards the intake manifold side of the head. This results in a more gradual turn the air and fuel mixture will have to make on its way down into the bore. An air/fuel mixture doesn't like to make sharp turns or crash into steep walls, etc. Think of it as being more like Talladega than Martinsville.
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The SCJ intake port (bottom) has a much higher short turn. |
The new SCJ heads incorporate all of these changes with a few extras. The exhaust valve was moved toward the intake side of the head. This was done primarily to make the port longer. In the old head, the exhaust had to make a terribly sharp turn in order to fit the low header placement. The longer port on the new version makes for a more gradual turn. The exhaust valve wedge angle was also changed from 15 degrees to 4 degrees. This makes the floor of the exhaust port, or "short turn" taller, resulting in an even more gradual turn.
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The intake for the SCJ, on the left is slightly shorter and wider at the short turn than the CJ, on the right. |
With the valves being moved, the rocker bosses needed to be repositioned and angled differently to accommodate the adjustments. New guide plates, unique to these heads, were then manufactured and the spark plugs were positioned deeper into the head at different angles, keeping the wire end near the original placement.
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The exhaust ports in the SCJ (bottom) are slightly larger and have smoother casting than the CJ (top). |
With all of the modifications completed to both heads, it was back to the dyno. The first run produced a little over 700HP. With great relief, we looked forward to some serious dyno testing.
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Notice how drastic the difference in chamber and valve location is between the CJ (left) and the SCJ (right). |
First we thought we would try a little more cam. Right out of Crane's book we picked an R-268/420-2-10 P/N 358821 cam. It measures 268 degrees intake, 278 degrees exhaust, @.050", .718 lift, 110 degree lobe center. This cam change resulted in an increase of 55-60 HP. We were now at 755HP. Ford's crate motor required a slight piston valve notch adjustment (intake only) to run this cam. We used an Isky tool, run with a drill using the SCJ head as a fixture, right in the dyno room. Thank God for a 6HP Sears shop vac! It only took about 30 seconds per piston. The new cam needed a better valve spring and retainer (more installed height and pressure). At this point we changed to the original CJ heads with a power loss back to 665HP. With the larger cam, the new SCJ was 90 HP better. Talk about things working together! All CJ and SCJ heads now come with 2.200 intake valves. Some heads manufactured in the last five years, have had a problem with the valves scraping each other. To remedy this, they reduced the valve size from 2.250 to 2.200. The new SCJ heads will accept the larger valve with no problem. With a larger intake valve and corresponding valve job, we saw an increase of 15 HP, up to 770. We feel that at about 700 HP and above, the bigger valve is worth looking into, but with a smaller cam or less cubic inches, there wouldn't be much difference.
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The upper two punch marks are indicating the SCJ guide centers, while the lower marks are old CJ locations. |
The last thing we tried was porting the last 2" of the Ford/Victor intake manifold. By making it closer to the size of the head, it gained 10 HP. Our final record for power was 781! You have to admit that's not bad for streetable compression (10:1). I see no reason why a good 600" race motor with these heads wouldn't make 900+ HP.
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Notice how close this valve is to the simulated bore in the older CJ head. |
This example takes a look at how much room the line of sight flow path, has to make its turn. |
This cylinder head surpassed our wildest expectations and was ready to take to the market. On a snowy February morning in 2001, Alan Root and I presented this head to the Ford Racing Technologies Team in Romulus, Mich., for consideration. On hand to hear our findings were: Angelo Giampetroni, Ed Lyons, and Jim Long. We presented an hour long "dog and pony show" on why this head was better, why they needed it, and why they should scrap the existing CJ head. We left Michigan with a firm commitment that they wanted the head.
At that point, Root Industries took over the project. At that time, all we had were two working prototypes with more weld and epoxy than original aluminum. From these samples, Root built completely new patterns and production tooling to mass-produce the new SCJ heads. The first articles were dyno tested in August 2001 at JKRE and then at Ford Motorsport. The first run of heads was shipped in the fall.
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Another view of the CJ with a valve close to the bore. |
There is a lot of room around this intake valve. These heads need only 28 degrees of total timing. (5 degrees less than the CJ.) |
Throughout the process, one thing has been consistent with this cylinder head; everyone that has run it has seen an increase in power. The more aggressive the engine (cu. in., cam size, compression, carb size, etc.) the more increase in horsepower. Keep in mind that we are comparing the new SCJ head to a head that is very good when compared to what previously existed. The old tried and true CJ aluminum is at least 100 HP better than most base 429-460 cast iron heads.
If there is any one thing that is magic on the SCJ head, it is the intake valve placement and angle. As compared to other passenger car style heads, (low intake port entry) you won't find a head that will out flow it at .500-.550 valve lift.
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This example shows no room around the intake. |
A lot of room around the intake is depicted in this photo. |
Ford bought a generous supply of these cylinder heads, and I believe their current inventory will last at least another six months. The M-6049-SCJ cylinder head (page 44, 2003 Ford Motorsports Catalog) is available at Jon Kaase Racing Engines, 770-307-0241, or through any of the Ford Motorsport dealers.
Notes on airflow
Most high flowing intake ports that have the entry down close to the deck have trouble with turbulence at high valve lifts. Ford Cleveland cast iron or aluminum heads were famous for this. The air will break away from the floor as it approaches the valve seat and starts to tumble. The problem is in the sharp turn it has to make going uphill, and then trying to turn straight down. If it were an airplane wing, we would call it a stall. The SCJ heads share this personality with their cousin from Cleveland. The only thing I can say about this is that we don't know how much of a problem this is when the engine is actually running. During our testing we tried all different tricks and styles of porting to get rid of the turbulence. To be honest, we never saw any difference in the power. We had heads that leveled off at .550 lift with 360cfm and ported the short turns on the same heads where they flowed 390cfm at .700. It just didn't seem to matter; the heads made good power regardless of airflow. About once a year we will pick up the airflow in our 815" hemi heads, lose 50 HP, and then unplug the flowbench for another year.
Notes on Ford's 514-crate motor
The 514 is a remarkable engine. They are all first class parts that will take real punishment. We made hundreds of dyno pulls with only one minor problem, and it was pilot error. We had the heads off and on so many times, that it was losing a little oil each time. I noticed it lost a little oil pressure at the end of every run, but I was in denial. Did it kill the bearings? Of course! Did we have to rebuild the whole motor right in the middle of testing? Of course! The reality is that the 4.3"stroke crank likes to suck all the oil out of the uncovered oil sump of a pan that's a little too small. Find a good windage tray and a better pan that will fit your car.
Piston/Valve clearance
The exhaust valve will never hit because it is up in the head really far. The intake is a little more delicate. On a crate motor, with it's 254 degree intake lobe at 111 degree centerline, you will have about .080" piston to valve clearance. That would be just enough. It should always be checked though. The SCJ heads should clear the pistons with just about any street performance cam. If you need a little more room, the Isky tool is a great thing!
Other Important Facts
You can mill these heads all you want. The deck is .625" and the intake seat is deep in the head. You will not mill the seat away.
The pushrod lengths in our crate motor were 8.850" intake, 9.150 Exhaust. Original CJ pushrods were all 8.550". You can figure you need .300" longer intake, .600 longer exhaust.
The existing supply of CJ heads is about to run out. I believe all the crate motors built from now on will have the new SCJ heads on them.
We have stud girdles in stock for either cylinder head in stock.
