#9---C.N.C. Super Prepped Heads

6/27/2014


     CNC SUPER PREPPED HEAD (updated6/7/12)
Mopar Muscle Magazine asked us to send them a tech article on these heads and we thought it would be a good thing to adapt it to our website so that you could see what you will get when you order these heads. This entire article may or may not end up in its complete form in the magazine...but here, at HughesEngines.com, we give you the full meal deal!

    Cylinder heads and their modifications are always a hot topic of conversation among gearheads, from rank amateurs to the top of the heap, professionals. Big ports, small ports, high velocity, reversion, C.F.M., F.P.M., etc. are all jargon that needs to be understood to enter into these high tech discussions, however, once into conversations you will likely find lots of disagreement on what is and what is not important.
    Any engine can benefit from some sort of air flow increase whether it’s a custom high flow valve & seat job on a Resto-Cruiser or a Hot Street car that includes a bowl porting. For the Hot Street and Street/Strip engine on a budget the question is what gives the most bang for the buck? Part of that answer will be how much bang do you want?
    The cost of ported heads directly relates to how much work is put into the heads along with how productive it is. The most bang for the buck comes from improving the low and mid-lift flow, for many reasons. First of all the price will be lower because of the time it takes to do the job. Any flow increases at low and mid-lift will benefit the total air flow available twice, once when the valve is opening and once more when the valve is closing. Whereas at maximum lift, the valve is only in that position for a short period of time reducing it’s contribution to the total flow. If the possibility exists that the heads may be completely C.N.C. or fully hand ported at a later time, what is done now, if done properly, should not have a negative effect on that later work.
    We will try to give you some ideas on what to expect from the porting that Hughes Engines calls their CNC SUPER PREPPED HEADS, for small blocks, when applied to the popular Edelbrock aluminum heads.

    The most important area of the port is the valve seat and the one half inch area before and after the seat. The actual seat, its angles and widths are the most critical areas and receive as much attention during research and development of the ports as the rest of the entire
 

port. With that in mind, Hughes Engines concentrates on the seat area to start with. The intake seat is generally comprised of a number of special angles and widths. These angles and widths will vary with the configuration of the port and valve. The angles and widths are
 

designed to improve the low and mid-lift air flow and wet flow. Low and mid-lift flow should not be confused with low and mid-rpm power output. More flow thru the valve & seat area, at ANY lift, helps power at ALL RPM levels.    

    The exhaust seat is a different deal and incorporates some radii’s along with angles.  The area below the seat is called the throat and transitions into the bowl. Each of these areas is customized into the seat and eventually into the runner.  The area above the seat is blended into the chamber. This blending may include opening the chamber wall to unshroud the valve, especially around the intake valve. Blending may also include laying back the wall of the chamber directly across from the intake valve. All these are dependent on the port, seat, chamber, etc. In some heads these modifications are very productive; others it is a waste of time or can even hurt the air flow and power.  Testing is the only way to know.
    The seat area and valve angles have the greatest effect on the air flow up to about .350” to.400”lift.. The port runner shape, size and finish have little effect up to that point. Above this lift point the port shape & size of the port starts to affect the flow. The seat area, although still effective, is not the major influence on the flow from about .400” lift on up. 
    A major mistake among new or inexperienced engine builders is to look for the maximum air flow at peak lift. What you should be concerned with is the “area under the curve”. One of the things you will learn when porting cylinder heads is that you have trade-offs. You can concentrate on high lift flow at the expense mid-lift flow and vise-versa. You should make a choice that gives you the most area under the curve. This means more flow at each lift point.  
    A port that flows 15CFM more at .600” lift is not nearly as good as one that flows 15 CFM more at .300” lift, especially if you only have .600” lift.

    In photo 1 we see a stock Edelbrock L.A. and Mopar Performance chamber and valve seats. The small block Edelbrock head flows up to 40 CFM more than the iron L.A. heads like the “X” and “J” that they replace. They have smaller combustion chambers and have a 
double quench area, just what the doctor ordered.

    Photo 2 shows the chamber and seats after Hughes Engines newest C.N.C. Super Prep work. The intake seats are a multitude of proprietary angles and widths. The exhaust is based more on radii’s than angles on edges. The reason for the angles on the intake is for more fuel shear and better wet flow characteristics.  
 With the Hughes seat the angle 45 ºactually sets a little proud from the other angles, Photo 3 -vs- photo 4.This helps the wet flow and can be cut when the heads are freshened without altering the seat width. 




   The CNC machined chamber un-shrouds the intake valve increasing the air flow and encourages better wet flow in the chamber. Better wet flow increases power through better burning.
    Photos 5 &6 shows the before and after pictures of the port opening. The porting work at the gasket is Hughes’ deep port match and is part of the CNC Super Prep work.


   

Chart # 2  shows the out-of-the box air flow on both the intake and exhaust ports. This chart show the air flow on the same flow bench after the seat & port work, and what the chamber work does for you. The flow figures shown are the average of 3 different ports. It is important to note that the heads were flowed on the same bench before and after so the gains are accurate and relative.

 

Chart #2: These were new Edlebrock 60779 (LA) or Mopar P5153849 heads just out of the box. All numbers are checked & corrected @28”.
Chart  #2      Out of Box Test
 
Intake cfm
 
Exhaust cfm w/o pipe
.100”
67.6
 
 
.200”
128.0
 
84.4
.300”
185.2
 
129.8
.350”
208.1
 
142.6
.400”
227.1
 
151.2
.450”
240.6
 
157.2
.500”
253.7
 
161.2
.550”
256.4
 
163.3
.600”
257.7
 
164.2

Notice how the stock intake flow levels off at about .500”. That pattern will continue throughout the other  upgrades. To increase the flow above .500” will require the complete port to be opened up.

                         Chart #3 is the same ports on Edlebrock 60779 (LA) or Mopar P5153849 with Hughes Engines CNC super prepped porting modifications. 
Lift
INT cfm
Flow Gain cfm
 
EXH cfm
w/o pipe


Gain cfm
.100”
72.1
+4.5 
------
-------
.200”
150.4
+22.4
87.0
+3.4
.300”
209.5
+24.3
136.5
+6.7
.350”
231.3
+23.2
153.0
+10.4
.400”
248.5
+21.4
169.1
+17.3
.450”
257.0
+16.4
178.4
+21.2
.500”
252.9
-.8
182.2
+22.9
.550”
253.2
-3.2
186.6
+23.3
.600”
254.4
-3.3
188.7
+24.5
.650
256.4
+4.2
189.8
+24.9
 

    We also do this same work on the Edelbrock 61779 (Magnum) heads. 
The Mopar P5153847 head can be ported this same way.

Test Lift Stock int. cfm CNC S/P Intake Int. Flow Increase Stock Exh CFM CNC S/P Exh Exh. FLow Increase
.100 67.6 72.7 5.1      
.200 124.6 150.7 26.1 78.3 89.7 11.4
.300 181.5 206.4 24.9 132.2 138.7 6.5
.350 204.2 230.0 25.8 147.2 162.3 15.1
.400 224.9 249.8 24.9 162.3 177.4 150.1
.450 236.2 259.6 23.4 171.8 191.4 19.6
.500 246.5 265.5 19.0 180.8 199.8 19.0
.550 247.8 267.3 16.5 187.2 204.9 17.7
.600 244.5 265.0 20.5 192.5 209.1 16.6
.650 245.5 265.9 20.7 196.7 212.2 15.5

 
The chamber work helped both the intake and exhaust sides, but that work was much more effective on the intake side. This indicates the shrouding on the intake side is much greater than the exhaust side, and it indicates the potential when these heads are properly worked. The seat and port work were more effective on the exhaust side at higher lift.
 What do these charts tell you? On the Intakes side you can see that the Intake flow shot up at 200”, 300”, 350” and .400”. An amazing 22 to 24 CFM and these double digit increases stayed around up to 450”. Above that lift a tiny bit of flow was lost, however the tremendous gains below that more than offset this insignificant loss. Plus the gains were at the lowest lifts where the valve spends more time because it is there twice in each cycle (remember?)

On the Exhaust side, the gains are greater at higher lift because the port is considerably shorter. This flow improvement helps to reduce reversion. Reversion is the effect we see at the overlap point when the Intake valve is just opening and the Exhaust valve is just about to close. This is when the exhaust gas can flow up the Intake port, diluting the intake charge. The greater the overlap of both valves the greater the reversion. The art of building engines is filled with trade-offs and overlap is one of them.
    Let’s talk about the slight flow loss on the Intake from 500” lift. Cylinder head ports are passages with twists, turns and restrictions. As a restriction is removed the flow goes up, but there are still some restrictions left. As the restrictions that effect flow at lower lifts are eliminated, the flow volume increases to a point that pre-existing restrictions that were not problems, now become problems. This causes the flow at high lifts to stagnate somewhat. The ports can be fully C.N.C. ported and 2.08 valves installed which will remove most all of the restrictions and flow a lot more air “for a few more dollars”.
And if you are really power hungry, Hughes can move the intake pushrod over .200” and supply off-set rockers, photo #9.    The combustion chamber work will enlarge the chamber volume about 3-4 cc. Normally we will mill the head a few thousandths to return the volume to stock size. These CNC Super Prepped heads work well for hot street applications, all street/strip applications and in a budget oriented strip only application.
    So, O.K., how much power are the Hughes C.N.C. Super Prepped heads worth over out of the box heads? This depends on how the engine is built. On a 360 C.I. with a mild cam, good dual plane intake, headers and a true 10.5:1 compression ratio (Aluminum Heads must run more compression the iron heads), C.N.C. Super Prep work might be worth 20 – 30 more HP. On a Hot 408 C.I. or 416 C.I. stroker you might be looking at 30 – 50 more HP.
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